Difference between revisions of "Anatomical Record 21-22 (1921)"

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==A contribution to the early development of the heart in mammalia, with special reference to the guinea-pig==
 
==A contribution to the early development of the heart in mammalia, with special reference to the guinea-pig==
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{{Ref-Yoshinaga1921}}
  
TANZO YOSHINAGA
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Tanzo Yoshinaga
  
 
Department of Anatomy, University of Michigan
 
Department of Anatomy, University of Michigan
  
TWENTY-THREE FIGURES
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Twenty-Three Figures
  
INTRODUCTION
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===Introduction===
  
 
Since the fundamental investigations on the development of the heart in mammals by His, Born, and others were published, many prominent investigators have contributed to our knowledge concerning the earlier stages of development of the heart and of the pericardial cavity in representatives of almost all classes of vertebrates. The earlier workers began their investigations after the developmental stage in which the embryonal heart tube had already assumed the complete S form. From the results of their work, however, only very general conclusions can be drawn. In many important details the literature shows contradictions, while each theory advanced has been supported by investigators of recognized ability.
 
Since the fundamental investigations on the development of the heart in mammals by His, Born, and others were published, many prominent investigators have contributed to our knowledge concerning the earlier stages of development of the heart and of the pericardial cavity in representatives of almost all classes of vertebrates. The earlier workers began their investigations after the developmental stage in which the embryonal heart tube had already assumed the complete S form. From the results of their work, however, only very general conclusions can be drawn. In many important details the literature shows contradictions, while each theory advanced has been supported by investigators of recognized ability.
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In the study of the early development of the heart and cranial blood vessels in ferret embryos, Wang agrees with Miss Parker in the absence of the ventral mesocardium, there being no fusion of this part of the pleuropericardial wall, nor that any part of the gut closure is effected by the fusion of the lateral folds.
 
In the study of the early development of the heart and cranial blood vessels in ferret embryos, Wang agrees with Miss Parker in the absence of the ventral mesocardium, there being no fusion of this part of the pleuropericardial wall, nor that any part of the gut closure is effected by the fusion of the lateral folds.
  
OBSERVATIONS
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===Observations===
  
 
Stage I
 
Stage I
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EARLY DEVELOPMENT OF HEART IN MAMMALIA
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In the younger stage the pericephaHc mesoderm is situated anterior to the pharyngeal membrane, approximately in the same horizontal plane with the embryonic shield (fig. 5B). But in this stage it is brought ventrally to the pharyngeal membrane, as the foregut has begun to develop; the reversal of the preumbilical portion of the embryonic body accompanies this development.
  
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C. In figure 10 is presented a drawing of a midsagittal section of an embryonic shield of a guinea pig, removed from the uterus fourteen days and twelve hours after insemination. This series includes 166 sections, having a 7 /x thickness. The figure is reproduced from a drawing of the eighty third section, passing through almost exactly parallel to the midaxis of the embryonic shield. As measured by age, this embryonic shield is slightly younger than that discussed under figure 9, but the general findings of the development are slightly in advance of that of the latter.
  
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The craniomedian limb of the pericardial cavity, which lies under the foregut, extends dorsocaudally in a cranioventral direction, and has increased its dimensions in both the ventrodorsal and craniocaudal directions (fig. 10). Compared with the foregoing embryo (fig. 9), its sagittal long axis forms an angle a little more acute with the longitudinal axis of the embryonic body. Its caudal half presents the crescentic coelom cleavage, directing its convexity caudo ventral ward, while its cranial half still remains as a lineal slit. The cranial extremity of the craniomedian limb of the pericardial cavity is practically situated on the same level with that of the head fold (fig. 10). It may be demonstrated, when we compare figures 9 and 10, that the backward movement of the foregut opening from the cranial extremity of the head fold is greater than the rate of progress of the head fold forward from a certain fixed point. This actual backward progress of the foregut opening brings about the lengthening of the foregut. The foregut in this embryo is longer than in the preceding embryo. Its cranial extremity is slightly caudad to that of the craniomedian limb of the pericardial cavity. The ventral wall of the foregut coalesces with the ectoderm, indicating the pharyngeal membrane, while its dorsal wall corresponds to the cranial end of the notochord. The entoderm, which forms the dorsocaudal wall of the craniomedian limb of the pericardial cavity, is reflected from the foregut opening to the ventral wall of the craniomedian limb of the pericardial cavity, representing the so-called cardiac fold (repli cardiaque Tourneux). The cranial wall of the craniomedian limb of the pericardial cavity is formed by the ectoderm, which is reflected from the pharyngeal membrane to the proamnionic region.
  
265
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A few cell strands of angioblasts can be seen between the mesoderm of the splanchnopleura and the underlying ectoderm. The splanchnopleura is present, its convexity turned caudoventrally, in accordance with the entodermic cardiac fold. Its central part has begun to invaginate into the pericardial cavity, rising from the underlying entoderm. Between these two layers the angioblasts are scattered.
  
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Stage III
  
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The material on which the description of stage III is based consists of two embryos, one of which was cut transversely and the other longitudinally.
  
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A. This specimen was removed from the uterus of a guineapig fifteen days and fourteen hours after insemination. This series includes 318 sections, having a 7 /^ thickness. The plastic reconstruction of the cephalic portion of the embryo was made with wax plates, and the whole shield, reconstructed for another purpose, was used for this study.
  
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The neural groove extends from the cranial end to the caudal amnion attachment. It is wide and shallow in the caudal portion, while it is narrow and deepens toward the head fold. The head fold is divided into two primary vesicles; the cranial vesicle is wide and long, projecting laterally and cranially over the cranial and lateral walls of the cranial body elevation. The caudal vesicle is small and passes insensibly into the spinal portion. The anlagen of the trigeminal ganglia, as well as the rudiment of the otic ganglia, are to be seen. Four somites are completely segmented, besides in their cranial and caudal territory, a somite is in process of formation. The dorsal aortae and the first aortic arch are present, while the ventral aortae are not yet completely differentiated. In the region of their anlagen the angioblasts are irregularly distributed. The foregut extends throughout twenty-two sections, appearing first in the twenty-seventh section and continuing to the forty-ninth section, while the craniomedian limb of the pericardial cavity extends throughout sixteen sections, appearing in the twenty-third section and continuing to the thirty-ninth section. The cranial end of the head fold appears in the eighth section, on account of the forward progress of the head fold. This fact can be demonstrated in the dorsal surface of the whole reconstruction model, in which the prominent swelUng of the dorsal surface of the pericardial cavity is much more distinct than that of the foregoing model. The cranial extremity of the pericardial cavity disappears under the head fold slightly caudad to its cranial margin.
  
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In this embryo the mesoderm of the splanchnopleural projects into the pericardial cavity, forming prominent folds, already presented in the previous stage, but in this stage is well developed. These folds are converted on both sides into continuous myocardial tubes. Their dorsal surfaces approach the dorsal wall of the pericardial cavity, coming nearly into contact with it. These lateral myocardial tubes are best developed at the level of the hindbrain, where they are relativel}' dilated and contain the well-developed endothelial tubes. On tracing cranial ward, both myocardial tubes gradually diminish in height and width, until they finally disappear opposite to the foregut opening on its left side, while on the right side the myocardial tube continues into the caudad portion of the craniomedian limb of the pericardial cavity, converting it into the prominent rounded ridge of the mesoderm of the splanchnopleura. In this region the thickened mesoderm of the splanchnopleura, present as a somewhat flattened fold, is elevated above the underlying entoderm. In the space between these two layers a number of angioblasts can be seen (fig. 11 and 12). In tracing still farther cranialward, the relatively thin layer of mesoderm of the splanchnopleura remains attached to the underlying entoderm; between them no angioblasts can be seen (fig. 13).
  
  
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Fig. 12 Dorsal view of the reconstruction of the same embryonic shield (stage III, A) from which figure 11 was drawn. Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. At the caudal part of the craniomedian limb of the perciardial cavity the splanchnopleura projects into the pericardial cavity, forming the prominent fold, which is absent in front of the cranial extremity of the myocardial tube on the left side. E-D indicates plane of section of figure 11. X 100.
  
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Fig. 13 Dorsal view of the reconstruction of the same embryonic shield (stage III, A) from which figures 11 and 12 were drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to show the underlying endothelial tubes and angioblasts. Angioblasts are scattered under the splanchnopleural fold at the cuadal part of the craniomedian limb of the pericardial cavity, almost connecting both cranial extremities of the lateral endothelial tubes. But angioblasts are absent in front of the cranial extremity of the lateral endothelial tube on the left side, where the splanchnopleura has not risen from the underlying entoderm. X 100.
  
  
  
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It can be ascertained that the formation of the mesodermal splanchnopleural folds occurs in loco and progresses cranialward, until both cranial extremities of the myocardial tubes will ultimately unite and communicate with each other at the craniomedian limb of the pericardial cavity. The craniomedian limb of the pericardial cavity increases its dimensions both in the ventrodorsal and in the craniocaudal directions, while the formation of the myocardial anlage in this portion remains in its primitive condition. In the hindbrain region the pericardial cavity reaches its maximum width in proportion to the myocardial and endothelial development. But it shows here a rather narrower space in the ventrodorsal direction, on account of the dorsal expansion of the myocardial tubes. In tracing still further caudalward, the pericardial cavity gradually narrows until it entirely disappears in the somitic region, parallel with the gradually diminishing splanchnopleural folds and endothelial tubes.
  
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The endothelial tubes are differentiated at great length, extending throughout nearly the whole extent of the lateral pericardial cavity. But in many places these tubes are irregularly interrupted, their continuity bridged by angioblast cords. The endothelial tubes terminate cranially opposite to the foregut opening on the right side and slightly caudad to it on the left side. In front of these terminations a number of angioblasts are scattered. Extending still farther ci'aniomedially, by means of these angioblasts, the cranial extremities of the endothelial tubes are connected with each other through the middle plane underneath the flat splanchnopleural folds of the craniomedian limb of the pericardial cavity (fig. 13). There is a distinct significance in the fact that these angioblasts are directly derived from the mesoderm of the splanchnopleural cells in loco. Moreover, in some other parts the angioblasts or endothelial cells are undoubtedly connected with the thickened and indented mesoderm of the splanchnopleura. Therefore, it is conceivable that the productive activity of these cells from the mesoderm of the splanchnopleura is still continued in this embryo.
  
  
Som
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Stage IV
  
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The material on which the following description of stage IV is based consists of two embryos, one of which was cut transversely and the other longitudinally.
  
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A. This specimen was removed from the uterus of a guineapig fourteen days and eight hours after insemination. This series includes 566 sections, having a o ^ thickness, from the cranial margin of the head fold to the caudal end of the mesodermic thickening of the allantois. The plastic reconstruction of the cephahc portion of the embryonic body was made with wax plates.
  
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The head fold has progressed cranial- and dorsalward. Its cephahc extremity is represented in that of the embryonic shield. There are present seven pairs of mesodermic somites, the first and last being small and indistinctly segmented. The neural groove extends from the cranial end to the caudal amnion attachment. In the hindbrain region the neural groove shows very narrow and deep as both the neural plates approach each other.
  
266 TANZO YOSHINAGA
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In the model it can be recognized that the craniomedian limb of the pericardial cavity increases its dimensions in the ventrodorsal direction, while its lateral and craniocaudal extent remains approximately unchanged in comparison with the previous stage III. The cranial extremity of this portion extends at its dorsal part into the mesodermic cavity of the mandibular region on both sides. While their outhne gradually approaches the horizontal plane, the caudal extremity of this portion is continued into both the lateral pericardial cavities, which gradually diminish in width caudalward. In the region of the second somite they entirely disappear.
  
In the younger stage the pericephaHc mesoderm is situated anterior to the pharyngeal membrane, approximately in the same horizontal plane with the embryonic shield (fig. 5B). But in this stage it is brought ventrally to the pharyngeal membrane, as the foregut has begun to develop; the reversal of the preumbilical portion of the embryonic body accompanies this development.
+
The formation of both the lateral myocardial tubes, which has been discussed in stage III, are considerably developed and have so far progressed cranialward, that their cranial portions have partially come into contact and been fused together. Through this portion the myocardial tubes communicate with each other. On the dorsal surface of this fused portion of the lateral myocardial tubes the myocardial \Yalls are reflected directly onto the dorsal wall of the pericardimn, thus forming the dorsal mesocardium on both sides. Between the lateral mesocardial layers there is present an irregular triangular space, which we purpose to designate as the intermesocardial space and through which the endothelial offshoots come out from the myocardial cavity onto the space between the mesocardial layers and the floor of the foregut. Its apex is directed craniaiward, where the lateral mesocardial layers come in contact, marking the cranial margin of the communicating myocardial cavity. Its basal portion is directed caudalward and corresponds to the foregut opening, by which the lateral mesocardium layers diverge from each other and continue farther caudalward along the lateral myocardial tubes (fig. 14). Between the abovementioned adherent cranial margin of the mesocardium and the foregut opening, the lateral myocardial cavities communicate with each other across the middle plane to the extent of eight sections. From this communicating myocardial cavity are sent out two short cranial diverticula on either side, separated by a septal wall in the middle plane, corresponding to the cranial extremities of the lateral myocradial tubes. These diverticula are present as the rounded myocardial horns, directed cranialward and separated from each other by their own inner walls. These inner walls are caudally converted into a wedge-shaped prominent ridge, which continues into the communicating portion of the myocardial cavit}^ and gradually diminishes caudalward (fig. 15). The communicating portions of the lateral mj'^ocardial tubes are directly continued into the lateral myocardial tubes caudolaterally on both sides and they are separated from each other by the foregut opening. The ventral wall of the communicating portion of the myocardial cavity is reflected onto the ventral wall of the pericardium and is recognized only in the caudal portion. The reflection points from the myocardium to the ventral pericardial wall are fused together at the cranial part, but at the caudal part the reflection points diverge from each other and a triangular space remains between them in just the same manner as can be seen in the dorsal wall.
  
C. In figure 10 is presented a drawing of a midsagittal section of an embryonic shield of a guinea pig, removed from the uterus fourteen days and twelve hours after insemination. This series includes 166 sections, having a 7 /x thickness. The figure is reproduced from a drawing of the eighty third section, passing through almost exactly parallel to the midaxis of the embryonic shield. As measured by age, this embryonic shield is slightly younger than that discussed under figure 9, but the general findings of the development are slightly in advance of that of the latter.
 
  
The craniomedian limb of the pericardial cavity, which lies under the foregut, extends dorsocaudally in a cranioventral direction, and has increased its dimensions in both the ventrodorsal and craniocaudal directions (fig. 10). Compared with the foregoing embryo (fig. 9), its sagittal long axis forms an angle a little more acute with the longitudinal axis of the embryonic body. Its caudal half presents the crescentic coelom cleavage, directing its convexity caudo ventral ward, while its cranial half still remains as a lineal slit. The cranial extremity of the craniomedian limb of the pericardial cavity is practically situated on the same level with that of the head fold (fig. 10). It may be demonstrated, when we compare figures 9 and 10, that the backward movement of the foregut opening from the cranial extremity of the head fold is greater than the rate of progress of the head fold forward from a certain fixed point. This actual backward progress of the foregut opening brings about the lengthening of the foregut. The foregut in this embryo is longer than in the preceding embryo. Its cranial extremity is slightly caudad to that of the craniomedian limb of the pericardial cavity. The ventral wall of the foregut
+
This ventral triangular space is covered by the entoderm cephalad to the foregut opening, while the dorsal intermesocardial space is covered by the foregut floor. Ventrall}" to the communicating mj'ocardial cavity, the pericardial cavity passes from side to side, because of the absence of the ventral mesocardium. Along the ventral mesodermic reflection the anlage of the septum transversum of His will be presented in the future development, and the mesodermic reflection may be erroneously taken for the ventral mesocardium, if a single section of this portion should be examined, as many workers claim the existence of the ventral mesocardium in mammals.
  
  
  
EARLY DEVELOPMENT OF HEART IN MAMMALL\ 267
 
  
coalesces with the ectoderm, indicating the pharyngeal membrane, while its dorsal wall corresponds to the cranial end of the notochord. The entoderm, which forms the dorsocaudal wall of the craniomedian limb of the pericardial cavity, is reflected from the foregut opening to the ventral wall of the craniomedian limb of the pericardial cavity, representing the so-called cardiac fold (repli cardiaque Tourneux). The cranial wall of the craniomedian limb of the pericardial cavity is formed by the ectoderm, which is reflected from the pharyngeal membrane to the proamnionic region.
+
Fig. 14 Dorsal view of the reconstruction of an embryonic shield (stage IV). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The two lateral myocardial tubes are partially confluent, slightly cephalad to the foregut opening. The two short cranial horns of the myocardial tubes are directed toward the top of the page. X 100.
  
A few cell strands of angioblasts can be seen between the mesoderm of the splanchnopleura and the underlying ectoderm. The splanchnopleura is present, its convexity turned caudoventrally, in accordance with the entodermic cardiac fold. Its central part has begun to invaginate into the pericardial cavity, rising from the underlying entoderm. Between these two layers the angioblasts are scattered.
+
Fig. 15 Dorsal view of the reconstruction of the same embryonic shield (stage IV) from which figure 14 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the underlying endothelial tubes. The two lateral endothelial tubes approach most closely to each other at the confluent myocardial portion, where independent endothelial cells are interposed between the two tubes. X 100.
  
Stage III
 
  
The material on which the description of stage III is based consists of two embryos, one of which was cut transversely and the other longitudinally.
 
  
A. This specimen was removed from the uterus of a guineapig fifteen days and fourteen hours after insemination. This series includes 318 sections, having a 7 /^ thickness. The plastic reconstruction of the cephalic portion of the embryo was made with wax plates, and the whole shield, reconstructed for another purpose, was used for this study.
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The endothelial tubes are well developed and are enclosed within the myocardial cavities on both sides. Their lumina are patent throughout their cranial extent, their cranial extremities terminate blindly opposite to the cranial extremities of the myocardial tubes, where the myocardial tubes are projected into the pericardial cavity, like the rounded lateral horns on either side, which contain the cranial extremities of the myocardial cavity. In tracing caudally, the endothelial tubes reduce their caUbers gradually and they are irregularly interrupted in their continuity by angioblasts. They entirely disappear in the somitic portion, where the lateral pericardial cavities assume a narrow and horizontal space and the splanchnopleural folds have entirely disappeared. The lateral endothelial tubes are most remarkably dilated and considerably approximated to each other at the communicating myocardial cavity, where the independent intermediate endothelial cells can be seen between the endothelial tubes. Throughout many sections in the communicating myocardial cavity, the endothelial tubes give off their endothelial offshoots from their dorsomedian aspects, coursing dorsolateralward, between the dorsal mesocardium and the floor of the foregut. These offshoots may be considered the future truncus arteriosus.
  
The neural groove extends from the cranial end to the caudal amnion attachment. It is wide and shallow in the caudal portion, while it is narrow and deepens toward the head fold. The head fold is divided into two primary vesicles; the cranial vesicle is wide and long, projecting laterally and cranially over the cranial and lateral walls of the cranial body elevation. The caudal vesicle is small and passes insensibly into the spinal portion. The anlagen of the trigeminal ganglia, as well as the rudiment of the otic ganglia, are to be seen. Four somites
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Owing to the gradual transition from these dilated endothelial tubes into the portion of the vitelline veins caudalward, their demarcation cannot be pointed out on the endothelial tubes nor on the myocardial tubes.
  
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The dorsal aortae and the first aortic arch are completely developed, while the ventral aortae are incompletely differentiated. In their anlagen a number of angioblasts are distributed irregularly.
  
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Stage V
  
268 TANZO YOSHINAGA
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The material on which the following description of stage V is based consists of two embryonic shields, which were cut transversely The partial plastic reconstruction of the cephalic portion and the reconstruction of the whole embryonic shield, made for another purpose, were used for this study.
  
are completely segmented, besides in their cranial and caudal territory, a somite is in process of formation. The dorsal aortae and the first aortic arch are present, while the ventral aortae are not yet completely differentiated. In the region of their anlagen the angioblasts are irregularly distributed. The foregut extends throughout twenty-two sections, appearing first in the twenty-seventh section and continuing to the forty-ninth section, while the craniomedian limb of the pericardial cavity extends throughout sixteen sections, appearing in the twenty-third section and continuing to the thirty-ninth section. The cranial end of the head fold appears in the eighth section, on account of the forward progress of the head fold. This fact can be demonstrated in the dorsal surface of the whole reconstruction model, in which the prominent swelUng of the dorsal surface of the pericardial cavity is much more distinct than that of the foregoing model. The cranial extremity of the pericardial cavity disappears under the head fold slightly caudad to its cranial margin.
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A. This specimen was removed from the uterus of a guinea pig fourteen days and eight hours after insemination. The series includes 612 sections, having a 5 m thickness. As measured by age, this embryonic shield is shghtly younger than that discussed in stage IV. As judged by the stage of general development, it is slightly more advanced, indicated by the facts that eight somites are present and that the medullary groove is much deeper and narrower in the hindbrain region, so that to a great extent both neural plates are in contact; here it passes insensibly into the spinal region. The forebrain plate still remains wide open, projecting cranially and laterally over the cranial and lateral wall of the anterior body elevation. It is, moreover, bent considerably ventralward. In the model it can easily be recognized that, owing to the fact that this embryonic shield is considerably folded off from the yolk sac, it is in general thicker in the ventrodorsal diameter and narrower in the lateral diameter than that in stage IV. In accordance therewith, the cranial extremities of the lateral myocardial tubes are forming a more acute angle than that of the previous stage. The craniomedian hmb of the pericardial cavity increases its ventrodorsal and craniocaudal dimensions, while its lateral diameter diminishes on comparison with the embryo of stage IV, in proportion to the rounded outUne of this embryo. The craniomedian Umb of the pericardial cavity is elongated at its dorsal part into the mandibular mesoderm. In coursing caudalward, the lateral pericardial cavities graduallj^ diminish their width, and at the same time their outline approaches the horizontal plane as a whole. They disappear entirely opposite to the fourth somite. The direction of the lateral myocardial tubes tends to their nmning parallel to each other. The lateral myocardial tubes are considerably dilated at their cranial portion, where they abruptly become voluminous in comparison with their caudal portion. The transitional points of these two different portions are situated a little caudad to the foregut opening on both sides, where the myocardial tubes mark shght indentations. These indentations indicate the future atrioventricular constriction (fig. 16).
  
In this embryo the mesoderm of the splanchnopleural projects into the pericardial cavity, forming prominent folds, already presented in the previous stage, but in this stage is well developed. These folds are converted on both sides into continuous myocardial tubes. Their dorsal surfaces approach the dorsal wall of the pericardial cavity, coming nearly into contact with it. These lateral myocardial tubes are best developed at the level of the hindbrain, where they are relativel}' dilated and contain the well-developed endothelial tubes. On tracing cranial ward, both myocardial tubes gradually diminish in height and width, until they finally disappear opposite to the foregut opening on its left side, while on the right side the myocardial tube continues into the caudad portion of the craniomedian limb of the pericardial cavity, converting it into the prominent rounded ridge of the mesoderm of the splanchnopleura. In this region the thickened mesoderm of the splanchnopleura, present as a somewhat flattened fold, is elevated above the underlying entoderm. In the space between these two layers a number of angioblasts can be seen (fig. 11 and 12). In tracing still farther cranialward, the relatively thin layer of mesoderm
+
The cranial extremities of the lateral myocardial tubes become more voluminous as compared with those of the previous stage and are projected cephalad into the pericardial cavity as large lateral rounded horns. They are separated from each other by their own inner walls, which fuse caudally into one septal wall and, as we trace still farther caudally, we find them converted into the prominent wedge-shaped ridge which projects into the communicating myocardial cavity. This ridge gradually diminishes in height caudalward until it has entirely disappeared in the middle of the communicating cavity (fig. 17).
  
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The dorsal wall of the fused myocardial tubes is reflected directly onto the dorsal wall of the pericardium, forming the dorsal mesocardium on both sides. These lateral mesocardial layers come to fusion in a region a little cephalad to the foregut opening, where it makes the cranial margin of the communicating myocardial cavity. On the dorsal surface of the fused myocardial portion an irregular intermesocardial space can be seen, covered by the floor of the foregut. Its apex is directed cephalad, corresponding to the point where the lateral mesocardium layers are fused together. Its base is directed caudad, corresponding to the foregut' opening. Its sides are formed by the lateral mesocardial layers. Corresponding to this intermesocardial space, the lateral myocardial tubes communicate with each other through the median plane throughout the extent of nine sections. In a similar way, the ventral wall of the fused myocardial tube is reflected onto the ventral wall of the pericardium, but only in its caudal portion. Between these two lines of the mesodermal reflection there remains a narrow space free from the mesoderm and covered directly by the entoderm. However, these lines of reflection on the ventral wall are disposed in a rather transverse direction and are located only for a short extent in the caudal part of the communicating myocardial tube, while on the dorsal surface the lines of reflection of the mesocardium are directed rather longitudinally and extend throughout the whole length of the eoniinunicating myocardinal tube. The communicating portion of the myocardial cavity terminates blindly in the cranial diverticulum cephalad, corresponding to the cranial extremities of the lateral myocardial tubes, while caudally it is elongated into the lateral myocardial tubes, which are diverged by the foregut opening, and their lumina are gradually diminished toward the somitic region.
  
  
EARLY DEVELOPMENT OF HEART IN MAMMALIA
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Fig. 16 Dorsal view of the reconstruction of an embryonic shield (stage V). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The two lateral myocardial tubes become quite voluminous, especially at their cranial portions, which continue farther caudalward, gradually diminishing in size. The atrioventricular constriction is marked on the surface of the myocardial tubes, caudad to the foregut opening on both sides. The two cranial horns of the myocardial tubes become enlarged, and they are directed toward the top of the page. X 100.
  
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Fig. 17 Dorsal view of the reconstruction of the same embryonic shield (stage V) from which figure 16 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the underlying endothelial tubes, which are apparently enlarged at their cranial portions, where they most nearly approach each other. X 100.
  
  
269
 
  
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In general, the endothelial tubes are much more developed than those of the previous stage, since they have become deeper and wider. At the widest portion of the endothelial tubes, corresponding to the communicating myocardial cavity, the endothehal tubes approach each other so that they come nearly into contact. On these portions, throughout many sections, the endothelial tubes give off a number of endothehal offshoots from their dorsomedian surface into the space between the dorsal mesocardium and the foregut floor. From these portions they become gradually narrower, toward both the cranial and caudal directions. The cranial extremities of the endothelial tubes terminate blindly opposite to the cranial myocardial extremities, while caudally they continue into the portion of the vitelline veins. The endothelial tubes assume the distinctly narrow calibers opposite to the atrioventricular constriction. The endothehal tubes sprout out into innumerable tenuous fibrils, often forming a feltwork, which occupies the ^^■ide space between the myocardium and the endothehum.
  
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The dorsal aortae and the first aortic arch are developed, while the ventral aortae are not completely formed, as in their anlagen a number of angioblasts are scattered.
  
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Stage VI
  
Fig. 12 Dorsal view of the reconstruction of the same embryonic shield (stage III, A) from which figure 11 was drawn. Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. At the caudal part of the craniomedian limb of the perciardial cavity the splanchnopleura projects into the pericardial cavity, forming the prominent fold, which is absent in front of the cranial extremity of the myocardial tube on the left side. E-D indicates plane of section of figure 11. X 100.
+
The material on which the following description of stage VI is based consists of one embryo, cut transversely. The plastic reconstruction of the cephalic portion of the embryo was made with wax plates.
  
Fig. 13 Dorsal view of the reconstruction of the same embryonic shield (stage III, A) from which figures 11 and 12 were drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to show the underlying endothelial tubes and angioblasts. Angioblasts are scattered under the splanchnopleural fold at the cuadal part of the craniomedian limb of the pericardial cavity, almost connecting both cranial extremities of the lateral endothelial tubes. But angioblasts are absent in front of the cranial extremity of the lateral endothelial tube on the left side, where the splanchnopleura has not risen from the underlying entoderm. X 100.
+
This specimen was removed from the uterus of a guinea pig fourteen days and eight hours after insemination. The series includes 582 sections, having a 5 micron thickness. As measured by age, this embryonic shield is the same as that of the previous embryo. As reckoned by general development and special development of the heart, it is considerably advanced over the preceding embryo. Eight well-segmented somites are present. The medullary groove, extending from the cranial end to the caudal amnion attachment, is as deep and narrow as in the previous embryo. The form of the embryonic shield is, in general, more rounded in comparison than with the foregoing embryo, as the ventrodorsal diameter of this embryo is apparently increased while its lateral diameter has remained unchanged. The first visceral pouch and the oral pit are developed ; in these places the entoderm coalesces intimately with the ectoderm.
  
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The reconstruction shows that at this stage of development the craniomedian limb of the pericardial cavity increases considerably in the craniocaudal dimension and in the ventrodorsal dimension. The craniomedian limb of the pericardial cavity communicates caudally with the lateral pericardial cavities. On coursing caudally, these become gradually narrower, until they disappear entirely opposite to the sixth somite. The craniomedian limb of the pericardial cavity is elongated cranially at its dorsal part into the mandibular portion, lying under the foregut floor. The caudal half of the ventral surface of the craniomedian limb of the pericardial cavity is covered by the yolk sac, while its cranial half and all other surfaces are covered by the amnion.
  
 +
In this stage the fused portion of the lateral myocardial tubes increases remarkably throughout its craniocaudal extent. In accordance therewith, the cranial bilateral myocardial horns, which correspond to the cranial extremities of the lateral myocardial tubes, and predominate in the craniomedian limb of the pericardial cavity in the previous stage, apparently diminish their dimensions in this embryo, and show only their rudiments. They assume only short and wide bilateral processes, divided by a shallow and wide intervening groove. In the previous stage this groove was present as a narrow and deep sulcus. Subsequently, the inner walls of these horns diverged markedly from each other (fig. 18). The wedge-shaped ridge which, in the previous stage, projected into the communicating myocardial cavity at its middle cranial wall, as a caudal continuation of the converted septum walls of the cranial bilateral myocardial horns, is considerably retired cranialward in this embryo. Therefore, the cranial wall of the communicating myocardial cavity approaches in such a manner toward the cranial wall of the pericardium as to come nearly into contact with it and, simultaneously, the communicating myocardial cavity is elongated cranialward. The fused portion of the myocardial tube becomes distinctly narrower and thicker in comparison with that of the previous stage. In two of the same magnified models ( X300) the widest lateral diameter of this portion is calculated as 14.5 cm. in this embryo, instead of 19 cm. of the previous embryo, while the ventrodorsal diameter of this portion presents 5.1 cm. in this embryo and 3 cm. in the former embryo. The fused myocardial tube is reflected directly onto the dorsal wall of the pericardium, ?,nd thus forms the dorsal mesocardium on both sides. Between the lateral mesocardial layers there can be seen alongrectangularintermesocardial space; its
 +
plane is approximately parallel with the horizontal. Its cranial margin is formed by the fused portion of the mesocardial layers in the middle line; its caudal margin corresponds to the foregut opening, while both lateral margins are represented by the lateral mesocardial layers, which continue farther caudalward, diverted by the foregut opening. In accordance with this mesocardial space, both myocardial tubes communicate freely with each other through the median plane, and thus form
  
THE ANATOMICAL RECORD, VOL. 21, NO. 3
 
  
  
  
270 TANZO YOSHINAGA
+
Fig. 18 Dorsal view of the reconstruction of an embryonic shield (stage VI). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The confluent portion of the two lateral myocardial tubes is considerably elongated in the craniocaudal direction. The two cranial horns of the myocardial tubes diminish to short rudiments, as their septal wall retires cranialward. They are directed toward the top of the page. X 100.
  
of the splanchnopleura remains attached to the underlying entoderm; between them no angioblasts can be seen (fig. 13).
 
  
It can be ascertained that the formation of the mesodermal splanchnopleural folds occurs in loco and progresses cranialward, until both cranial extremities of the myocardial tubes will ultimately unite and communicate with each other at the craniomedian limb of the pericardial cavity. The craniomedian limb of the pericardial cavity increases its dimensions both in the ventrodorsal and in the craniocaudal directions, while the formation of the myocardial anlage in this portion remains in its primitive condition. In the hindbrain region the pericardial cavity reaches its maximum width in proportion to the myocardial and endothelial development. But it shows here a rather narrower space in the ventrodorsal direction, on account of the dorsal expansion of the myocardial tubes. In tracing still further caudalward, the pericardial cavity gradually narrows until it entirely disappears in the somitic region, parallel with the gradually diminishing splanchnopleural folds and endothelial tubes.
 
  
The endothelial tubes are differentiated at great length, extending throughout nearly the whole extent of the lateral pericardial cavity. But in many places these tubes are irregularly interrupted, their continuity bridged by angioblast cords. The endothelial tubes terminate cranially opposite to the foregut opening on the right side and slightly caudad to it on the left side. In front of these terminations a number of angioblasts are scattered. Extending still farther ci'aniomedially, by means of these angioblasts, the cranial extremities of the endothelial tubes are connected with each other through the middle plane underneath the flat splanchnopleural folds of the craniomedian limb of the pericardial cavity (fig. 13). There is a distinct significance in the fact that these angioblasts are directly derived from the mesoderm of the splanchnopleural cells in loco. Moreover, in some other parts the angioblasts or endothelial cells are undoubtedly connected with the thickened and indented mesoderm of the splanchnopleura. Therefore, it is conceivable that the productive activity of these cells from the mesoderm of the splanchnopleura is still continued in this embryo.
+
Fig. 19 Dorsal view of the reconstruction of the same embryonic shield (stage VI) from which figure 18 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the endothelial tubes. The two lateral endothelial tubes have fused and communicate with each other at a middle third of the ventricle, where they most closely approach each other in figure 17. The lateral endothelial tubes apparently diminish their size opposite to the atrioventricular constriction. X 100.
  
 +
the craniomedian limb of the myocardial cavity. This limb of the myocardial cavity is bifurcated caudally into the lateral myocardial tubes, which are diverged from each other by the foregut opening and in which the viteUine veins are enclosed, leading cranially into the craniomedian limb of the myocardial cavity (fig. 19). In brief, the myocardial anlage presents cranially two short rudimentary horns, which terminate blindly as the cranial myocardial extremities, while caudally there are two lateral myocardial prolongations, into which the vitelUne veins enter. Between these four extremities the myocardial wall is relatively considerably expanded dorsal, lateral, ventralward and contains the widest portions of the endothehal tubes, which are united in the communicating cavity. This region corresponds to the future ventricle region. On the midsagittal hne of the ventral surface of this fused myocardial portion a shallow longitudinal groove can be seen.
  
 +
On the ventral aspect of the fused myocardial portion the ventral myocardial layer is reflected onto the ventral wall of the pericardium, but this is limited to a short length, extending only to the caudal part of this portion.
  
EARLY DEVELOPMENT OF HEABT IN M.IMAIALIA 271
+
The transition from the cranial expanding ventricle to the caudal myocardial prolongations is indicated by an annular constriction, which is produced by the infolding of the whole myocardial wall, a little deeper on the right side than on the left. This indicates the atrioventricular constriction and is situated at the level slightly cephalad to the foregut opening on both sides.
  
Stage IV
+
Proceeding caudally from this constriction, the lateral myocardial tubes reduce their calibers abruptly and diverge from each other. On the surface of these caudal prolongations of the myocardial tubes there are present indefinite, shallow indentations at the level shghtly caudad to the foregut opening, and these constrictions have been regarded as the future sinoatrial construction.
 
 
The material on which the following description of stage IV is based consists of two embryos, one of which was cut transversely and the other longitudinally.
 
 
 
A. This specimen was removed from the uterus of a guineapig fourteen days and eight hours after insemination. This series includes 566 sections, having a o ^ thickness, from the cranial margin of the head fold to the caudal end of the mesodermic thickening of the allantois. The plastic reconstruction of the cephahc portion of the embryonic body was made with wax plates.
 
 
 
The head fold has progressed cranial- and dorsalward. Its cephahc extremity is represented in that of the embryonic shield. There are present seven pairs of mesodermic somites, the first and last being small and indistinctly segmented. The neural groove extends from the cranial end to the caudal amnion attachment. In the hindbrain region the neural groove shows very narrow and deep as both the neural plates approach each other.
 
 
 
In the model it can be recognized that the craniomedian limb of the pericardial cavity increases its dimensions in the ventrodorsal direction, while its lateral and craniocaudal extent remains approximately unchanged in comparison with the previous stage III. The cranial extremity of this portion extends at its dorsal part into the mesodermic cavity of the mandibular region on both sides. While their outhne gradually approaches the horizontal plane, the caudal extremity of this portion is continued into both the lateral pericardial cavities, which gradually diminish in width caudalward. In the region of the second somite they entirely disappear.
 
 
 
The formation of both the lateral myocardial tubes, which has been discussed in stage III, are considerably developed and have so far progressed cranialward, that their cranial portions have partially come into contact and been fused together. Through this portion the myocardial tubes communicate with each other. On the dorsal surface of this fused portion of the
 
 
 
 
 
 
 
272 TANZO YOSHINAGA
 
 
 
lateral myocardial tubes the myocardial \Yalls are reflected directly onto the dorsal wall of the pericardimn, thus forming the dorsal mesocardium on both sides. Between the lateral mesocardial layers there is present an irregular triangular space, which we purpose to designate as the intermesocardial space and through which the endothelial offshoots come out from the myocardial cavity onto the space between the mesocardial layers and the floor of the foregut. Its apex is directed craniaiward, where the lateral mesocardial layers come in contact, marking the cranial margin of the communicating myocardial cavity. Its basal portion is directed caudalward and corresponds to the foregut opening, by which the lateral mesocardium layers diverge from each other and continue farther caudalward along the lateral myocardial tubes (fig. 14). Between the abovementioned adherent cranial margin of the mesocardium and the foregut opening, the lateral myocardial cavities communicate with each other across the middle plane to the extent of eight sections. From this communicating myocardial cavity are sent out two short cranial diverticula on either side, separated by a septal wall in the middle plane, corresponding to the cranial extremities of the lateral myocradial tubes. These diverticula are present as the rounded myocardial horns, directed cranialward and separated from each other by their own inner walls. These inner walls are caudally converted into a wedge-shaped prominent ridge, which continues into the communicating portion of the myocardial cavit}^ and gradually diminishes caudalward (fig. 15). The communicating portions of the lateral mj'^ocardial tubes are directly continued into the lateral myocardial tubes caudolaterally on both sides and they are separated from each other by the foregut opening. The ventral wall of the communicating portion of the myocardial cavity is reflected onto the ventral wall of the pericardium and is recognized only in the caudal portion. The reflection points from the myocardium to the ventral pericardial wall are fused together at the cranial part, but at the caudal part the reflection points diverge from each other and a triangular space remains between them in just the same manner as can be seen in the dorsal wall.
 
 
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA
 
 
 
 
 
 
 
273
 
 
 
 
 
 
 
This ventral triangular space is covered by the entoderm cephalad to the foregut opening, while the dorsal intermesocardial space is covered by the foregut floor. Ventrall}" to the communicating mj'ocardial cavity, the pericardial cavity passes from side to side, because of the absence of the ventral mesocardium. Along the ventral mesodermic reflection the anlage of the septum transversum of His will be presented in the future development, and the mesodermic reflection may be erroneously taken for
 
 
 
 
 
 
 
 
 
Fig. 14 Dorsal view of the reconstruction of an embryonic shield (stage IV). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The two lateral myocardial tubes are partially confluent, slightly cephalad to the foregut opening. The two short cranial horns of the myocardial tubes are directed toward the top of the page. X 100.
 
 
 
Fig. 15 Dorsal view of the reconstruction of the same embryonic shield (stage IV) from which figure 14 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the underlying endothelial tubes. The two lateral endothelial tubes approach most closely to each other at the confluent myocardial portion, where independent endothelial cells are interposed between the two tubes. X 100.
 
 
 
 
 
 
 
274 TANZO YOSHINAGA
 
 
 
the ventral mesocardium, if a single section of this portion should be examined, as many workers claim the existence of the ventral mesocardium in mammals.
 
 
 
The endothelial tubes are well developed and are enclosed within the myocardial cavities on both sides. Their lumina are patent throughout their cranial extent, their cranial extremities terminate blindly opposite to the cranial extremities of the myocardial tubes, where the myocardial tubes are projected into the pericardial cavity, like the rounded lateral horns on either side, which contain the cranial extremities of the myocardial cavity. In tracing caudally, the endothelial tubes reduce their caUbers gradually and they are irregularly interrupted in their continuity by angioblasts. They entirely disappear in the somitic portion, where the lateral pericardial cavities assume a narrow and horizontal space and the splanchnopleural folds have entirely disappeared. The lateral endothelial tubes are most remarkably dilated and considerably approximated to each other at the communicating myocardial cavity, where the independent intermediate endothelial cells can be seen between the endothelial tubes. Throughout many sections in the communicating myocardial cavity, the endothelial tubes give off their endothelial offshoots from their dorsomedian aspects, coursing dorsolateralward, between the dorsal mesocardium and the floor of the foregut. These offshoots may be considered the future truncus arteriosus.
 
 
 
Owing to the gradual transition from these dilated endothelial tubes into the portion of the vitelline veins caudalward, their demarcation cannot be pointed out on the endothelial tubes nor on the myocardial tubes.
 
 
 
The dorsal aortae and the first aortic arch are completely developed, while the ventral aortae are incompletely differentiated. In their anlagen a number of angioblasts are distributed irregularly.
 
 
 
Stage V
 
 
 
The material on which the following description of stage V is based consists of two embryonic shields, which were cut trans
 
 
 
 
 
EARLY DEVELOPAIENT OF HEART IN MAMMALIA 275
 
 
 
verselj^ The partial plastic reconstruction of the cephalic portion and the reconstruction of the whole embryonic shield, made for another purpose, were used for this study.
 
 
 
A. This specimen was removed from the uterus of a guinea pig fourteen days and eight hours after insemination. The series includes 612 sections, having a 5 m thickness. As measured by age, this embryonic shield is shghtly younger than that discussed in stage IV. As judged by the stage of general development, it is slightly more advanced, indicated by the facts that eight somites are present and that the medullary groove is much deeper and narrower in the hindbrain region, so that to a great extent both neural plates are in contact; here it passes insensibly into the spinal region. The forebrain plate still remains wide open, projecting cranially and laterally over the cranial and lateral wall of the anterior body elevation. It is, moreover, bent considerably ventralward. In the model it can easily be recognized that, owing to the fact that this embryonic shield is considerably folded off from the yolk sac, it is in general thicker in the ventrodorsal diameter and narrower in the lateral diameter than that in stage IV. In accordance therewith, the cranial extremities of the lateral myocardial tubes are forming a more acute angle than that of the previous stage. The craniomedian hmb of the pericardial cavity increases its ventrodorsal and craniocaudal dimensions, while its lateral diameter diminishes on comparison with the embryo of stage IV, in proportion to the rounded outUne of this embryo. The craniomedian Umb of the pericardial cavity is elongated at its dorsal part into the mandibular mesoderm. In coursing caudalward, the lateral pericardial cavities graduallj^ diminish their width, and at the same time their outline approaches the horizontal plane as a whole. They disappear entirely opposite to the fourth somite. The direction of the lateral myocardial tubes tends to their nmning parallel to each other. The lateral myocardial tubes are considerably dilated at their cranial portion, where they abruptly become voluminous in comparison with their caudal portion. The transitional points of these two different portions are situated a little caudad to the foregut opening on both sides,
 
 
 
 
 
 
 
276 TANZO YOSHINAGA
 
 
 
where the myocardial tubes mark shght indentations. These indentations indicate the future atrioventricular constriction
 
 
 
(fig. 16).
 
 
 
The cranial extremities of the lateral myocardial tubes become more voluminous as compared with those of the previous stage and are projected cephalad into the pericardial cavity as large lateral rounded horns. They are separated from each other by their own inner walls, which fuse caudally into one septal wall and, as we trace still farther caudally, we find them converted into the prominent wedge-shaped ridge which projects into the communicating myocardial cavity. This ridge gradually diminishes in height caudalward until it has entirely disappeared in the middle of the communicating cavity (fig. 17).
 
 
 
The dorsal wall of the fused myocardial tubes is reflected directly onto the dorsal wall of the pericardium, forming the dorsal mesocardium on both sides. These lateral mesocardial layers come to fusion in a region a little cephalad to the foregut opening, where it makes the cranial margin of the communicating myocardial cavity. On the dorsal surface of the fused myocardial portion an irregular intermesocardial space can be seen, covered by the floor of the foregut. Its apex is directed cephalad, corresponding to the point where the lateral mesocardium layers are fused together. Its base is directed caudad, corresponding to the foregut' opening. Its sides are formed by the lateral mesocardial layers. Corresponding to this intermesocardial space, the lateral myocardial tubes communicate with each other through the median plane throughout the extent of nine sections. In a similar way, the ventral wall of the fused myocardial tube is reflected onto the ventral wall of the pericardium, but only in its caudal portion. Between these two lines of the mesodermal reflection there remains a narrow space free from the mesoderm and covered directly by the entoderm. However, these lines of reflection on the ventral wall are disposed in a rather transverse direction and are located only for a short extent in the caudal part of the communicating myocardial tube, while on the dorsal surface the lines of reflection of the mesocardium are directed rather longitudinally and extend
 
 
 
 
 
 
 
E.\IILY DEVELOPMENT OF HEART IN MAMMALIA
 
 
 
 
 
 
 
277
 
 
 
 
 
 
 
throughout the whole length of the eoniinunicating myocardinal tube. The communicating portion of the myocardial cavity terminates blindly in the cranial diverticulum cephalad, cor
 
 
 
 
 
 
 
Fig. 16 Dorsal view of the reconstruction of an embryonic shield (stage V). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The two lateral myocardial tubes become quite voluminous, especially at their cranial portions, which continue farther caudalward, gradually diminishing in size. The atrioventricular constriction is marked on the surface of the myocardial tubes, caudad to the foregut opening on both sides. The two cranial horns of the myocardial tubes become enlarged, and they are directed toward the top of the page. X 100.
 
 
 
Fig. 17 Dorsal view of the reconstruction of the same embryonic shield (stage V) from which figure 16 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the underlying endothelial tubes, which are apparently enlarged at their cranial portions, where they most nearly approach each other. X 100.
 
 
 
 
 
 
 
278 TANZO YOSHINAGA
 
 
 
responding to the cranial extremities of the lateral myocardial tubes, while caudally it is elongated into the lateral myocardial tubes, which are diverged by the foregut opening, and their lumina are gradually diminished toward the somitic region.
 
 
 
In general, the endothelial tubes are much more developed than those of the previous stage, since they have become deeper and wider. At the widest portion of the endothelial tubes, corresponding to the communicating myocardial cavity, the endothehal tubes approach each other so that they come nearly into contact. On these portions, throughout many sections, the endothelial tubes give off a number of endothehal offshoots from their dorsomedian surface into the space between the dorsal mesocardium and the foregut floor. From these portions they become gradually narrower, toward both the cranial and caudal directions. The cranial extremities of the endothelial tubes terminate blindly opposite to the cranial myocardial extremities, while caudally they continue into the portion of the vitelline veins. The endothelial tubes assume the distinctly narrow calibers opposite to the atrioventricular constriction. The endothehal tubes sprout out into innumerable tenuous fibrils, often forming a feltwork, which occupies the ^^■ide space between the myocardium and the endothehum.
 
 
 
The dorsal aortae and the first aortic arch are developed, while the ventral aortae are not completely formed, as in their anlagen a number of angioblasts are scattered.
 
 
 
Stage VI
 
 
 
The material on which the following description of stage VI is based consists of one embryo, cut transversely. The plastic reconstruction of the cephalic portion of the embryo was made with wax plates.
 
 
 
This specimen was removed from the uterus of a guinea pig fourteen days and eight hours after insemination. The series includes 582 sections, having a 5 // thickness. As measured by age, this embryonic shield is the same as that of the previous embryo. As reckoned by general development and special de
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 279
 
 
 
velopment of the heart, it is considerably advanced over the preceding embryo. Eight well-segmented somites are present. The medullary groove, extending from the cranial end to the caudal amnion attachment, is as deep and narrow as in the previous embryo. The form of the embryonic shield is, in general, more rounded in comparison than with the foregoing embryo, as the ventrodorsal diameter of this embryo is apparently increased while its lateral diameter has remained unchanged. The first visceral pouch and the oral pit are developed ; in these places the entoderm coalesces intimately with the ectoderm.
 
 
 
The reconstruction shows that at this stage of development the craniomedian limb of the pericardial cavity increases considerably in the craniocaudal dimension and in the ventrodorsal dimension. The craniomedian limb of the pericardial cavity communicates caudally with the lateral pericardial cavities. On coursing caudally, these become gradually narrower, until they disappear entirely opposite to the sixth somite. The craniomedian limb of the pericardial cavity is elongated cranially at its dorsal part into the mandibular portion, lying under the foregut floor. The caudal half of the ventral surface of the craniomedian limb of the pericardial cavity is covered by the yolk sac, while its cranial half and all other surfaces are covered by the amnion.
 
 
 
In this stage the fused portion of the lateral myocardial tubes increases remarkably throughout its craniocaudal extent. In accordance therewith, the cranial bilateral myocardial horns, which correspond to the cranial extremities of the lateral myocardial tubes, and predominate in the craniomedian limb of the pericardial cavity in the previous stage, apparently diminish their dimensions in this embryo, and show only their rudiments. They assume only short and wide bilateral processes, divided by a shallow and wide intervening groove. In the previous stage this groove was present as a narrow and deep sulcus. Subsequently, the inner walls of these horns diverged markedly from each other (fig. 18). The wedge-shaped ridge which, in the previous stage, projected into the communicating myocardial cavity at its middle cranial wall, as a caudal continuation
 
 
 
 
 
 
 
280
 
 
 
 
 
 
 
TANZO YOSHINAGA
 
 
 
 
 
 
 
of the converted septum walls of the cranial bilateral myocardial horns, is considerably retired cranialward in this embryo. Therefore, the cranial wall of the communicating myocardial cavity approaches in such a manner toward the cranial wall of the pericardium as to come nearly into contact with it and, simultaneously, the communicating myocardial cavity is elongated cranialward. The fused portion of the myocardial tube
 
 
 
 
 
 
 
 
 
Fig. 18 Dorsal view of the reconstruction of an embryonic shield (stage VI). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The confluent portion of the two lateral myocardial tubes is considerably elongated in the craniocaudal direction. The two cranial horns of the myocardial tubes diminish to short rudiments, as their septal wall retires cranialward. They are directed toward the top of the page. X 100.
 
 
 
 
 
 
 
becomes distinctly narrower and thicker in comparison with that of the previous stage. In two of the same magnified models ( X300) the widest lateral diameter of this portion is calculated as 14.5 cm. in this embryo, instead of 19 cm. of the previous embryo, while the ventrodorsal diameter of this portion presents 5.1 cm. in this embryo and 3 cm. in the former embryo. The fused myocardial tube is reflected directly onto the dorsal wall of the pericardium, ?,nd thus forms the dorsal mesocardium on both sides. Between the lateral mesocardial layers there can be seen alongrectangularintermesocardial space; its
 
 
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 281
 
 
 
plane is approximately parallel with the horizontal. Its cranial margin is formed by the fused portion of the mesocardial layers in the middle line; its caudal margin corresponds to the foregut opening, while both lateral margins are represented by the lateral mesocardial layers, which continue farther caudalward, diverted by the foregut opening. In accordance with this mesocardial space, both myocardial tubes communicate freely with each other through the median plane, and thus form
 
 
 
 
 
 
 
 
 
19
 
 
 
Fig. 19 Dorsal view of the reconstruction of the same embryonic shield (stage VI) from which figure 18 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the endothelial tubes. The two lateral endothelial tubes have fused and communicate with each other at a middle third of the ventricle, where they most closely approach each other in figure 17. The lateral endothelial tubes apparently diminish their size opposite to the atrioventricular constriction. X 100.
 
 
 
the craniomedian limb of the myocardial cavity. This limb of the myocardial cavity is bifurcated caudally into the lateral myocardial tubes, which are diverged from each other by the foregut opening and in which the viteUine veins are enclosed, leading cranially into the craniomedian limb of the myocardial cavity (fig. 19). In brief, the myocardial anlage presents cranially two short rudimentary horns, which terminate blindly as the cranial myocardial extremities, while caudally there are two lateral myocardial prolongations, into which the vitelUne veins enter. Between these four extremities the myocardial wall is relatively considerably expanded dorsal, lateral, ventralward and
 
 
 
 
 
 
 
282 TANZO YOSHINAGA
 
 
 
contains the widest portions of the endothehal tubes, which are united in the communicating cavity. This region corresponds to the future ventricle region. On the midsagittal hne of the ventral surface of this fused myocardial portion a shallow longitudinal groove can be seen.
 
 
 
On the ventral aspect of the fused myocardial portion the ventral myocardial layer is reflected onto the ventral wall of the pericardium, but this is limited to a short length, extending only to the caudal part of this portion.
 
 
 
The transition from the cranial expanding ventricle to the caudal myocardial prolongations is indicated by an annular constriction, which is produced by the infolding of the whole myocardial wall, a little deeper on the right side than on the left. This indicates the atrioventricular constriction and is situated at the level slightly cephalad to the foregut opening on both sides.
 
 
 
Proceeding caudally from this constriction, the lateral myocardial tubes reduce their calibers abruptly and diverge from each other. On the surface of these caudal prolongations of the myocardial tubes there are present indefinite, shallow indentations at the level shghtly caudad to the foregut opening, and these constrictions have been regarded as the future sinoatrial construction.
 
  
 
The lateral endothelial tubes are partially fused and their lumina communicate with each other, for their inner walls have been absorbed throughout seven sections. This portion is situated in the middle third of the bulging ventricle anlage, where in the previous stage both endothelial tubes were closely approximated and presented the greatest dilation and where in. this embryo also the endothehal tube is greatly expanded.
 
The lateral endothelial tubes are partially fused and their lumina communicate with each other, for their inner walls have been absorbed throughout seven sections. This portion is situated in the middle third of the bulging ventricle anlage, where in the previous stage both endothelial tubes were closely approximated and presented the greatest dilation and where in. this embryo also the endothehal tube is greatly expanded.
  
From this fused portion of the endothelial tube the two cranial horns and two caudal prolongations are given off. The bilateral cranial horns are short and gradually diminish in size cranialward, until they terminate in a pointed apex, opposite to the cranial extremities of the myocardial horns. From the dorsomedian part of these cranial endothelial horns a number of endothelial branches are given off. These endothehal
+
From this fused portion of the endothelial tube the two cranial horns and two caudal prolongations are given off. The bilateral cranial horns are short and gradually diminish in size cranialward, until they terminate in a pointed apex, opposite to the cranial extremities of the myocardial horns. From the dorsomedian part of these cranial endothelial horns a number of endothelial branches are given off. These endothehal branches are connected with the ventral aortae through the intermesocardial space.
 
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 283
 
 
 
branches are connected with the ventral aortae through the intermesocardial space.
 
  
 
Bilateral caudal prolongations are given off on both sides from the caudal aspect of the fused endothelial tube. Continuing caudalward, both endothelial tubes gradually diminish their cahbers, until the lumina have entirely disappeared at the atrioventricular constriction. Still further caudalward from this constriction, again they begin to dilate their calibers gradually and continue into the endothelial vitelline veins without any indication at their transitional point. At the atrioventricular constriction the endothelial tubes closely approach the infolding of the myocardial wall, while in the ventricle the intervening space between the myocardium and endothelium is relatively wide.
 
Bilateral caudal prolongations are given off on both sides from the caudal aspect of the fused endothelial tube. Continuing caudalward, both endothelial tubes gradually diminish their cahbers, until the lumina have entirely disappeared at the atrioventricular constriction. Still further caudalward from this constriction, again they begin to dilate their calibers gradually and continue into the endothelial vitelline veins without any indication at their transitional point. At the atrioventricular constriction the endothelial tubes closely approach the infolding of the myocardial wall, while in the ventricle the intervening space between the myocardium and endothelium is relatively wide.
Line 9,587: Line 9,439:
  
 
The specimen was removed from the uterus of a guinea-pig fourteen days and eleven hours after insemination. The series includes 418 sections, having a 7 ^ thickness, from the cephalic end of the head fold to the end of the mesodermic thickening of the allantois. Xine pairs of well-segmented somites were found, each somite showing a thick wall and enclosing a uniform cavity with a compact arrangement of cells, except two caudal somites, which contained no cavity nor presented the regular arrangement of the cells.
 
The specimen was removed from the uterus of a guinea-pig fourteen days and eleven hours after insemination. The series includes 418 sections, having a 7 ^ thickness, from the cephalic end of the head fold to the end of the mesodermic thickening of the allantois. Xine pairs of well-segmented somites were found, each somite showing a thick wall and enclosing a uniform cavity with a compact arrangement of cells, except two caudal somites, which contained no cavity nor presented the regular arrangement of the cells.
 
 
 
284 TANZO yOSHINAGA
 
  
 
The medullary canal is closed from the second somite to the last, but elsewhere the medullar}^ plates remain open. The notochordal plate is separated from the entoderm throughout from the second somite to the last, but elsewhere it is still connected with the entoderm. The first and second visceral pouches are developed, in which the ectoderm and entoderm have tightlycoalesced. The oral pit is formed and the pharyngeal membrane becomes quite thin.
 
The medullary canal is closed from the second somite to the last, but elsewhere the medullar}^ plates remain open. The notochordal plate is separated from the entoderm throughout from the second somite to the last, but elsewhere it is still connected with the entoderm. The first and second visceral pouches are developed, in which the ectoderm and entoderm have tightlycoalesced. The oral pit is formed and the pharyngeal membrane becomes quite thin.
Line 9,599: Line 9,447:
  
 
The myocardium presents cranially an undivided cranial extremity, which expands considerably in all directions and assumes a sac form, while caudally this myocardial sac is bifurcated into two rather slender myocardial prolongations, in which the endothelial vitelHne veins are enclosed on both sides. The transition from the cranial myocardial sac to the bilateral myocardial tubes is indicated by the deep atrioventricular construction, at the level slightly cephalad to the foregut opening. This constriction is produced by the infolding of the whole myocardial wall and shows apparently deeper on the right sidfe than on the left. On the ventral surface of the ventricle there can be seen a shallow groove in the midsagittal line at its caudal half, and in accordance therewith the whole thickness of the myocardial wall is slightly infolded into the myocardial cavity.
 
The myocardium presents cranially an undivided cranial extremity, which expands considerably in all directions and assumes a sac form, while caudally this myocardial sac is bifurcated into two rather slender myocardial prolongations, in which the endothelial vitelHne veins are enclosed on both sides. The transition from the cranial myocardial sac to the bilateral myocardial tubes is indicated by the deep atrioventricular construction, at the level slightly cephalad to the foregut opening. This constriction is produced by the infolding of the whole myocardial wall and shows apparently deeper on the right sidfe than on the left. On the ventral surface of the ventricle there can be seen a shallow groove in the midsagittal line at its caudal half, and in accordance therewith the whole thickness of the myocardial wall is slightly infolded into the myocardial cavity.
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA
 
 
 
 
285
 
 
 
  
 
This superficial groove and the infolding of the myocardial wall are located in the caudal half of the ventricle, for they gradually disappear toward its cranial extremity, which is of conical form. The ventral myocardial layer is reflected onto the ventral wall of the pericardium, but is confined to the atrial region to a short length opposite to the foregut opening.
 
This superficial groove and the infolding of the myocardial wall are located in the caudal half of the ventricle, for they gradually disappear toward its cranial extremity, which is of conical form. The ventral myocardial layer is reflected onto the ventral wall of the pericardium, but is confined to the atrial region to a short length opposite to the foregut opening.
 
 
 
 
D.M.
 
 
 
 
— AV.C.
 
 
  
  
 
Fig. 20 Dorsal view of the reconstruction of an embryonic shield (stage VII). Dorsal wall of the pericardium has been removed to show the pericardial cavity and the myocardial tubes. The myocardium shows cranially a single sac-formed ventricle, which bifurcates into two slender myocardial tubes caudalward. The transition between them is marked by the atrioventricular constriction cephalad to the foregut opening. A single cranial extremity of the ventricle is directed toward the top of the page. X 100.
 
Fig. 20 Dorsal view of the reconstruction of an embryonic shield (stage VII). Dorsal wall of the pericardium has been removed to show the pericardial cavity and the myocardial tubes. The myocardium shows cranially a single sac-formed ventricle, which bifurcates into two slender myocardial tubes caudalward. The transition between them is marked by the atrioventricular constriction cephalad to the foregut opening. A single cranial extremity of the ventricle is directed toward the top of the page. X 100.
  
On the dorsal aspect the myocardial wall is reflected onto the dorsal wall of the pericardium and forms the dorsal mesocardium on both sides. The cranial extremity of the dorsal mesocardial attachment corresponds to a middle third of the ventricle, and from this point it continues farther caudalward. Consequently, the cranial half of the ventricle is free from the mesocardium (fig. 20). Between the lateral mesocardial layers
+
On the dorsal aspect the myocardial wall is reflected onto the dorsal wall of the pericardium and forms the dorsal mesocardium on both sides. The cranial extremity of the dorsal mesocardial attachment corresponds to a middle third of the ventricle, and from this point it continues farther caudalward. Consequently, the cranial half of the ventricle is free from the mesocardium (fig. 20). Between the lateral mesocardial layers there can be seen an irregular triangular intermesocardial space. Its plane is directed caudodorsalward on account of the abrupt dorsal expansion of the ventricle. Its apex is, therefore, situated caudoventrally and is formed by the lateral mesocardial layers, approaching contact, opposite to the atrioventricular constriction, while its basal portion is directed craniodorsally and corresponds to the portion where the lateral mesocardial layers come to fusion and mark their cranial extremities.
 
 
 
 
 
 
286 TAXZO YOSHINAGA
 
 
 
there can be seen an irregular triangular intermesocardial space. Its plane is directed caudodorsalward on account of the abrupt dorsal expansion of the ventricle. Its apex is, therefore, situated caudoventrally and is formed by the lateral mesocardial layers, approaching contact, opposite to the atrioventricular constriction, while its basal portion is directed craniodorsally and corresponds to the portion where the lateral mesocardial layers come to fusion and mark their cranial extremities.
 
  
 
On the caudal surface of the ventricle the right half assumes an apparently wider dimension than the left. This is attributed partly to the exceeding expansion of the myocardial wall in the laterocaudal direction on the right half and partly to the deeper infolding of the atrioventricular constriction on the right side. On this bulging portion of the caudal extremity of the ventricle at the right half the caudal extremity of the right ventricle will be developed, and this is shown distinctly in the next stage.
 
On the caudal surface of the ventricle the right half assumes an apparently wider dimension than the left. This is attributed partly to the exceeding expansion of the myocardial wall in the laterocaudal direction on the right half and partly to the deeper infolding of the atrioventricular constriction on the right side. On this bulging portion of the caudal extremity of the ventricle at the right half the caudal extremity of the right ventricle will be developed, and this is shown distinctly in the next stage.
Line 9,639: Line 9,461:
 
On .the myocardial tubes of the atrial portion indefinite indentations, indicated as the sino-atrial constriction, can be recognized. These are between the atrioventricular constriction and the level of the pleuropericardial passages. This is especially noticeable on the left side.
 
On .the myocardial tubes of the atrial portion indefinite indentations, indicated as the sino-atrial constriction, can be recognized. These are between the atrioventricular constriction and the level of the pleuropericardial passages. This is especially noticeable on the left side.
  
The lateral endothelial tubes are fused together throughout the cranial two-thirds of the ventricle. Its cranial extremity terminates as a single conical apex opposite to the cranial extremity of the myocardial ventricle. At this fused portion the endothelial cavities communicate with each other and show considerable dilation. In tracing caudalward from this united portion, the tubes are separated from each other, even though they appear to approach each other. At the atrioventricular constriction the endothelial tubes present their smallest size and
+
The lateral endothelial tubes are fused together throughout the cranial two-thirds of the ventricle. Its cranial extremity terminates as a single conical apex opposite to the cranial extremity of the myocardial ventricle. At this fused portion the endothelial cavities communicate with each other and show considerable dilation. In tracing caudalward from this united portion, the tubes are separated from each other, even though they appear to approach each other. At the atrioventricular constriction the endothelial tubes present their smallest size and simultaneously they approach closely to each other. Proceeding still farther caudally from this portion, they are diverged from each other by the foregut opening and again assume a gradual enlargement of their calibers. At the caudal part of the ventricle, where the endothelial tubes are separated, they present an asymmetrical size, for the right one is extraordinarily de
 
 
 
 
 
 
EARLY DEVELOPAIENT OF HEART IN MAMMALIA
 
 
 
 
 
 
 
287
 
 
 
 
 
 
 
simultaneously they approach closely to each other. Proceeding still farther caudally from this portion, they are diverged from each other by the foregut opening and again assume a gradual enlargement of their calibers. At the caudal part of the ventricle, where the endothelial tubes are separated, they present an asymmetrical size, for the right one is extraordinarily de
 
  
  
Line 9,657: Line 9,467:
 
Fig. 21 Dorsal view of the reconstruction of the same embryonic shield (stage VII) from which figure 20 was drawn. Dorsal walls of the pericardium and of the myocardium have been removed to expose the endothelial tubes. The two lateral endothelial tubes have fused and communicate with each other throughout the cranial two-thirds of the ventricle. The ventricular endothelial tubes show a distinct asymmetrj^, due to the extraordinary enlargement of the right side, regardless of the fused or non-fused portion. The endothelial tube is elongated dorsalward from the dorsal surface of the enlarged right endothelial tube, passing through the intermesocardial space. This endothelial elongation is bifurcated into the two lateral branches, which are continuous into the ventral aortae. X 100.
 
Fig. 21 Dorsal view of the reconstruction of the same embryonic shield (stage VII) from which figure 20 was drawn. Dorsal walls of the pericardium and of the myocardium have been removed to expose the endothelial tubes. The two lateral endothelial tubes have fused and communicate with each other throughout the cranial two-thirds of the ventricle. The ventricular endothelial tubes show a distinct asymmetrj^, due to the extraordinary enlargement of the right side, regardless of the fused or non-fused portion. The endothelial tube is elongated dorsalward from the dorsal surface of the enlarged right endothelial tube, passing through the intermesocardial space. This endothelial elongation is bifurcated into the two lateral branches, which are continuous into the ventral aortae. X 100.
  
veloped and expended in the lateral and caudal directions, forming a curvature whose convexity is turned laterocaudalward. At this endothelial portion the endothelial tube is elongated vertically dorsalward and comes out from the myocardial cavity onto the foregut floor through the intermesocardial space. The cranial part of this endothelial elongation is bifurcated into two later branches which connect it cranially with the corresponding
+
veloped and expended in the lateral and caudal directions, forming a curvature whose convexity is turned laterocaudalward. At this endothelial portion the endothelial tube is elongated vertically dorsalward and comes out from the myocardial cavity onto the foregut floor through the intermesocardial space. The cranial part of this endothelial elongation is bifurcated into two later branches which connect it cranially with the corresponding ventral aortae. The asymmetrical development of the endotheUal ventricle corresponds to the myocardial asymmetry in the ventricle, which has been mentioned above. In this part of the ventrical the most important change will be noted in the next stage, here developing, namely, the right limb of the ventricle. And this change is initiated in this embryo as a considerable asymmetrical expansion of the caudal extremity of the ventricle on the right side.
 
 
 
 
 
 
288 TANZO YOSHINAGA
 
 
 
ventral aortae. The asymmetrical development of the endotheUal ventricle corresponds to the myocardial asymmetry in the ventricle, which has been mentioned above. In this part of the ventrical the most important change will be noted in the next stage, here developing, namely, the right limb of the ventricle. And this change is initiated in this embryo as a considerable asymmetrical expansion of the caudal extremity of the ventricle on the right side.
 
  
 
At the ventricle the endothelial tubes are separated from the myocardial wall by a wide intervening space, but they gradually approach each other in the direction of the atrioventricular constriction caudalward, as in the caudal part of the atrium no more intervening space can be pointed out between the myocardial wall and the endothelium (fig. 21).
 
At the ventricle the endothelial tubes are separated from the myocardial wall by a wide intervening space, but they gradually approach each other in the direction of the atrioventricular constriction caudalward, as in the caudal part of the atrium no more intervening space can be pointed out between the myocardial wall and the endothelium (fig. 21).
Line 9,675: Line 9,479:
 
The material on which the following description of stage VIII is based consists of one embryonic shield, which is cut transversely. The plastic reconstruction of the cephalic portion of the embryo was made; the reconstruction of the whole embryonic shield, made for another purpose, was used for this study.
 
The material on which the following description of stage VIII is based consists of one embryonic shield, which is cut transversely. The plastic reconstruction of the cephalic portion of the embryo was made; the reconstruction of the whole embryonic shield, made for another purpose, was used for this study.
  
This embryo was removed from the uterus of a guinea pig fourteen days and twelve hours after insemination. The series includes 408 sections, having a 10 m thickness, from the cephahc end of the head fold to near the caudal extremity of the allantoic mesodermic thickening. Nine pairs of the well-seg
+
This embryo was removed from the uterus of a guinea pig fourteen days and twelve hours after insemination. The series includes 408 sections, having a 10 m thickness, from the cephahc end of the head fold to near the caudal extremity of the allantoic mesodermic thickening. Nine pairs of the well-segmented somites are present and the tenth is in process of formation; each somite shows the thick wall and encloses a uniform cavity. The neural canal is closed from the region of the hindbrain to the region of the last somite, though in the foreand midbrain region it still remains open. The cranial flexure is shown in the region of the midbrain and that of the forebrain is bent downward and forward, bringing it to a plane parallel with the long axis of the hindbrain. The foregut is closed to the first somitic region. The first visceral pouch is found in the region of the midbrain with the entoderm and ectoderm coalesced, while the second visceral pouch is in process of formation also in the region of the hindbrain, in which region between the entoderm and ectoderm a thinner layer of the mesoderm than elsewhere is found interposes. The oral pit is well formed, the pharyngeal membrane is present as a thin single layer of cells. On the ventral surface of the model the edge of the foregut opening is elevated by two prominent Umbs, which on each side are confluent into an extensive ventral bulging cranially to the foregut opening. In position and direction this corresponds to the pericardial cavity, containing the voluminous heart.
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 289
 
 
 
mented somites are present and the tenth is in process of formation; each somite shows the thick wall and encloses a uniform cavity. The neural canal is closed from the region of the hindbrain to the region of the last somite, though in the foreand midbrain region it still remains open. The cranial flexure is shown in the region of the midbrain and that of the forebrain is bent downward and forward, bringing it to a plane parallel with the long axis of the hindbrain. The foregut is closed to the first somitic region. The first visceral pouch is found in the region of the midbrain with the entoderm and ectoderm coalesced, while the second visceral pouch is in process of formation also in the region of the hindbrain, in which region between the entoderm and ectoderm a thinner layer of the mesoderm than elsewhere is found interposes. The oral pit is well formed, the pharyngeal membrane is present as a thin single layer of cells. On the ventral surface of the model the edge of the foregut opening is elevated by two prominent Umbs, which on each side are confluent into an extensive ventral bulging cranially to the foregut opening. In position and direction this corresponds to the pericardial cavity, containing the voluminous heart.
 
  
 
The pericardial sac is closed except at the dorsomedian part of its caudal extremity, where the pleuropericardial passages are found. In the region of the sinus venosus each one of the bilateral pericardial cavities is divided into a median and a lateral part by the myocardial fold and in the region of the pleuropericardial passages the lateral parts of the bilateral pericardial cavities terminate blindly caudalward, so that only their median portions are continued caudally into the peritoneal cavity. Accordingly, these passages are represented merely by narrow, crescentic coelomic spaces, dorsomedian to the viteUine veins, proceeding caudally and mesially, crossing with the vitelline veins, which run cranially and mesially.
 
The pericardial sac is closed except at the dorsomedian part of its caudal extremity, where the pleuropericardial passages are found. In the region of the sinus venosus each one of the bilateral pericardial cavities is divided into a median and a lateral part by the myocardial fold and in the region of the pleuropericardial passages the lateral parts of the bilateral pericardial cavities terminate blindly caudalward, so that only their median portions are continued caudally into the peritoneal cavity. Accordingly, these passages are represented merely by narrow, crescentic coelomic spaces, dorsomedian to the viteUine veins, proceeding caudally and mesially, crossing with the vitelline veins, which run cranially and mesially.
  
 
On account of the considerable enlargement of the muscular heart, the pericardial space is, in general, proportionately reduced, especially in the well-developed ventricular portion a simple narrow space surrounds the muscular sac of the ventricle.
 
On account of the considerable enlargement of the muscular heart, the pericardial space is, in general, proportionately reduced, especially in the well-developed ventricular portion a simple narrow space surrounds the muscular sac of the ventricle.
 
 
 
290 TANZO YOSHINAGA
 
  
 
In the region of the atria and the sinus venosus a relatively wide space intervenes between the rather flat muscular tubes and the pericardial wall (fig. 22). There are present two distinct constrictions on the tubular muscular heart, infolding the whole thickness of the myocardial wall, one of which represents the atrioventricular constriction and the other the sino-atrial constriction.
 
In the region of the atria and the sinus venosus a relatively wide space intervenes between the rather flat muscular tubes and the pericardial wall (fig. 22). There are present two distinct constrictions on the tubular muscular heart, infolding the whole thickness of the myocardial wall, one of which represents the atrioventricular constriction and the other the sino-atrial constriction.
Line 9,700: Line 9,495:
 
At the caudal part of the ventricle, for a short length, both lateral limbs are divided into two completely independent cavities by the septal wall. The caudal extremity of the right ventricle is shown as the conical process, projecting caudolaterally and terminating blindly, while at the caudal extremity of the left ventricle the atrioventricular canal opens, which is formed by the infolding of the muscular wall, corresponding to the atrioventricular constriction.
 
At the caudal part of the ventricle, for a short length, both lateral limbs are divided into two completely independent cavities by the septal wall. The caudal extremity of the right ventricle is shown as the conical process, projecting caudolaterally and terminating blindly, while at the caudal extremity of the left ventricle the atrioventricular canal opens, which is formed by the infolding of the muscular wall, corresponding to the atrioventricular constriction.
  
The septal wall l^etween the two lateral limbs at the caudal part of the ventricle is farther continued cranialward and is converted into wedge-shaped prominent ridges at the inner sur
+
The septal wall l^etween the two lateral limbs at the caudal part of the ventricle is farther continued cranialward and is converted into wedge-shaped prominent ridges at the inner surface of the ventral and dorsal wall of the ventricle, in relation with longitudinal sulci on the external surface. These ridges have gradually disappeared within a caudal third of the ventricle (fig. 23). These prominent ridges show their anlage only on the ventral wall of the ventricle, near its caudal end, as seen in the previous stage. Consequently, there can be but little doubt that these folds cannot be regarded as the remnants of the primitive cardiac septum.
 
 
 
 
E.YRLY DEVELOPMENT OF HEART IN MAMMALIA
 
 
 
 
 
 
 
291
 
 
 
 
 
 
 
face of the ventral and dorsal wall of the ventricle, in relation with longitudinal sulci on the external surface. These ridges have gradually disappeared within a caudal third of the ventricle (fig. 23). These prominent ridges show their anlage only
 
 
 
 
 
 
 
S.A.C
 
  
 
 
P. P. P.
 
  
  
Line 9,727: Line 9,504:
  
  
 
on the ventral wall of the ventricle, near its caudal end, as seen in the previous stage. Consequently, there can be but little doubt that these folds cannot be regarded as the remnants of the primitive cardiac septum.
 
 
 
 
292 TANZO YOSHINAGA
 
  
 
The bulbus cordis is differentiated from the dorsal wall of the right ventricle near its cranial end, bulging out its wall cranial-dorsal and laterally. Its ventral wall is distinctly separated from the dorsal wall of the right ventricle at its cranial portion, projecting cranialward as an independent muscular sac, while in its caudal portion there can be noted no distinct demarcation between the wall of the bulbus cordis and that of the right ventricle. At the left and cranial sides of the bulboventricular junction, a deep external furrow can be seen, accompanied by a consequent infolding of the muscular w^all. On the right side the bulboventricular furrow is indefinitely marked only its cranial part, while in its caudal part it has disappeared entirely and insensibly continues into the dorsal wall of the right ventricle. On this account the bend of the heart tube at the bulboventricular junction is effected toward the right side, turning its concavity to the left side, beneath the left layer of the dorsal mesocardium.
 
The bulbus cordis is differentiated from the dorsal wall of the right ventricle near its cranial end, bulging out its wall cranial-dorsal and laterally. Its ventral wall is distinctly separated from the dorsal wall of the right ventricle at its cranial portion, projecting cranialward as an independent muscular sac, while in its caudal portion there can be noted no distinct demarcation between the wall of the bulbus cordis and that of the right ventricle. At the left and cranial sides of the bulboventricular junction, a deep external furrow can be seen, accompanied by a consequent infolding of the muscular w^all. On the right side the bulboventricular furrow is indefinitely marked only its cranial part, while in its caudal part it has disappeared entirely and insensibly continues into the dorsal wall of the right ventricle. On this account the bend of the heart tube at the bulboventricular junction is effected toward the right side, turning its concavity to the left side, beneath the left layer of the dorsal mesocardium.
Line 9,739: Line 9,510:
  
 
A single myocardial tube of the atria begins at the atrioventricular constriction cranially and continues into the sinus venosus caudally, demarcated by the sino-atrial constriction. This muscular tube shows a marked asymmetry on both sides, for the left side, being decidedly expanded in all directions in comparison with the right side, just contrary to the ventricle, in which the right side is apparently more voluminous than the left side and bulges considerably caudolaterally. Moreover, this opposing asymmetry must be attributed partly to the normal obliciue direction of the atrioventricular constriction.
 
A single myocardial tube of the atria begins at the atrioventricular constriction cranially and continues into the sinus venosus caudally, demarcated by the sino-atrial constriction. This muscular tube shows a marked asymmetry on both sides, for the left side, being decidedly expanded in all directions in comparison with the right side, just contrary to the ventricle, in which the right side is apparently more voluminous than the left side and bulges considerably caudolaterally. Moreover, this opposing asymmetry must be attributed partly to the normal obliciue direction of the atrioventricular constriction.
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA
 
 
 
 
293
 
 
  
  
Line 9,759: Line 9,521:
  
  
The cranial extremity of the atria opens into the left ventricle through the atrioventricular canal, which is situated on the left side from the midsagittal line, for the right atrioventricular constriction is apparently more deeply infolded and proportionately the prominent ridge at the inner wall is strongly pro
+
The cranial extremity of the atria opens into the left ventricle through the atrioventricular canal, which is situated on the left side from the midsagittal line, for the right atrioventricular constriction is apparently more deeply infolded and proportionately the prominent ridge at the inner wall is strongly projected into the canal on the right side. The caudal extremity of the atria is continued into the sinus venosus, which diverge from each other into the two lateral myocardial tubes in relation with the foregut opening. The demarcation of these different portions is indicated by the sino-atrial constriction, of which on the left side the myocardial wall is more deeply infolded than on the right side.
 
 
 
 
294 TANZO YOSHINAGA
 
 
 
jected into the canal on the right side. The caudal extremity of the atria is continued into the sinus venosus, which diverge from each other into the two lateral myocardial tubes in relation with the foregut opening. The demarcation of these different portions is indicated by the sino-atrial constriction, of which on the left side the myocardial wall is more deeply infolded than on the right side.
 
  
 
The two lateral layers of the dorsal mesocardium are fused together from a middle third of the ventricle to the cranial part of the atria; they are in close contiguity at the atrioventricular constriction, in which region the dorsal mesocardium is beginning to disappear in an embryo slightly older than that of this stage. But at the portion of the bulbus cordis and the caudal part of the atria, the layers of the dorsal mesocardium have not come in contact. The arterial opening is disposed nearly vertically, but slightly to the left side, through which the endothelial tube comes from the myocardial cavity, while the venous opening is disposed dorsocaudally and assumes an irregular triangular space. Its base is situated caudall}^ and \entrally opposite to the foregut opening, as a result of which the layers of the dorsal mesocardium divert together with the corresponding muscular tubes, which continue caudally. Its apex of the venous opening is directed cranialward and Ues at the higher horizontal level. Through this intermesocardial space the enclosed endothelial tube can be seen.
 
The two lateral layers of the dorsal mesocardium are fused together from a middle third of the ventricle to the cranial part of the atria; they are in close contiguity at the atrioventricular constriction, in which region the dorsal mesocardium is beginning to disappear in an embryo slightly older than that of this stage. But at the portion of the bulbus cordis and the caudal part of the atria, the layers of the dorsal mesocardium have not come in contact. The arterial opening is disposed nearly vertically, but slightly to the left side, through which the endothelial tube comes from the myocardial cavity, while the venous opening is disposed dorsocaudally and assumes an irregular triangular space. Its base is situated caudall}^ and \entrally opposite to the foregut opening, as a result of which the layers of the dorsal mesocardium divert together with the corresponding muscular tubes, which continue caudally. Its apex of the venous opening is directed cranialward and Ues at the higher horizontal level. Through this intermesocardial space the enclosed endothelial tube can be seen.
Line 9,770: Line 9,527:
 
On the ventral surface the myocardium is reflected onto the ventral wall of the pericardium at the sinus venosus. Here it can be observed that the mesodermal cells have proliferated to form an appreciable thickening around the endothelial tubes, indicating the future septum transversum.
 
On the ventral surface the myocardium is reflected onto the ventral wall of the pericardium at the sinus venosus. Here it can be observed that the mesodermal cells have proliferated to form an appreciable thickening around the endothelial tubes, indicating the future septum transversum.
  
The lateral endothelial tubes are fused in the middle third of the ventricle to the extent of fifteen sections. In this part they communicate with each other and the endothelial cavity is considerably dilated (fig. 23). This craniomedian part of the endothelial tube is bifurcated into the two cranial horns and two caudal prolongations. The cranial horns extend symmetrically from the cranial wall for a short distance on both sides
+
The lateral endothelial tubes are fused in the middle third of the ventricle to the extent of fifteen sections. In this part they communicate with each other and the endothelial cavity is considerably dilated (fig. 23). This craniomedian part of the endothelial tube is bifurcated into the two cranial horns and two caudal prolongations. The cranial horns extend symmetrically from the cranial wall for a short distance on both sides and terminate blindly opposite to the cranial myocardial extremity of the ventricle, which is of conical form.
 
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALL\ 295
 
 
 
and terminate blindly opposite to the cranial myocardial extremity of the ventricle, which is of conical form.
 
  
 
The right caudal prolongation is given off from the right side of its caudal wall and terminates as a short conical projection; its apical terminus is directed opposite to the caudal extremity of the right ventricle, conforming with it. The left caudal prolongation is given off from the left side of its caudal wall and caudally connects with the endothelial tubes of the atrium. These separate from each other and continue farther caudalward. From the origin of this left caudal prolongation caudally to the atrioventricular canal, that is, in the caudal part of the left ventricle, the two endothehal tubes show their smallest size and are very close in contact in some places, while in others the}- separate into two quite independent tubes with complete walls. Opposite to the atrioventricular canal the two endothelial tubes above mentioned begin definitely to separate into two lateral atrial endothehal tubes, increasing their calibers gradually caudalw^ard, while they lie approximately in a parallel direction.
 
The right caudal prolongation is given off from the right side of its caudal wall and terminates as a short conical projection; its apical terminus is directed opposite to the caudal extremity of the right ventricle, conforming with it. The left caudal prolongation is given off from the left side of its caudal wall and caudally connects with the endothelial tubes of the atrium. These separate from each other and continue farther caudalward. From the origin of this left caudal prolongation caudally to the atrioventricular canal, that is, in the caudal part of the left ventricle, the two endothehal tubes show their smallest size and are very close in contact in some places, while in others the}- separate into two quite independent tubes with complete walls. Opposite to the atrioventricular canal the two endothelial tubes above mentioned begin definitely to separate into two lateral atrial endothehal tubes, increasing their calibers gradually caudalw^ard, while they lie approximately in a parallel direction.
Line 9,784: Line 9,535:
 
In the ventricle the endothehal tubes are separated from the myocardial wall by a wide intervening space. In the atrium the intervening space becomes considerably narrower, and finally in the sinus venosus the endothehal tubes are enclosed intimately by their own independent myocardial wall, so that no appreciable space can be seen.
 
In the ventricle the endothehal tubes are separated from the myocardial wall by a wide intervening space. In the atrium the intervening space becomes considerably narrower, and finally in the sinus venosus the endothehal tubes are enclosed intimately by their own independent myocardial wall, so that no appreciable space can be seen.
  
The endothelial tube of the bulbus cordis extends from the dorsal surface of the right ventricular endothelium as its continuous prolongation. This endothelial tube proceeds at first
+
The endothelial tube of the bulbus cordis extends from the dorsal surface of the right ventricular endothelium as its continuous prolongation. This endothelial tube proceeds at first dorsocranially and then slightly toward the left side. This is enclosed by the corresponding myocardial wall of the bulbus cordis, which is closed cranially, but caudally opens and communicates with the ventricular cavity, as already mentioned. The right ventricular endothelium, which gives off the endothelial tube of the bulbus cordis, is fused together with the left one, but the left part of the fused ventricular endothelium participates in no way with the bulbus cordis.
 
 
 
 
 
 
296 TANZO YOSHINAGA
 
 
 
dorsocranially and then slightly toward the left side. This is enclosed by the corresponding myocardial wall of the bulbus cordis, which is closed cranially, but caudally opens and communicates with the ventricular cavity, as already mentioned. The right ventricular endothelium, which gives off the endothelial tube of the bulbus cordis, is fused together with the left one, but the left part of the fused ventricular endothelium participates in no way with the bulbus cordis.
 
  
 
The endothelium of the truncus arteriosus continues farther dorsally and slightly toward the left side from the bulbus cordis and passes through the above-mentioned arterial opening, and then bifurcates into lateral symmetrical branches, which are located between the foregut floor and the lateral dorsal mesocardial layers and continue farther cranially into the ventral aortae.
 
The endothelium of the truncus arteriosus continues farther dorsally and slightly toward the left side from the bulbus cordis and passes through the above-mentioned arterial opening, and then bifurcates into lateral symmetrical branches, which are located between the foregut floor and the lateral dorsal mesocardial layers and continue farther cranially into the ventral aortae.
Line 9,796: Line 9,541:
 
The first aortic arch and the ventral aortae are completely formed and the dorsal aortae are considerably elongated caudalward.
 
The first aortic arch and the ventral aortae are completely formed and the dorsal aortae are considerably elongated caudalward.
  
SUMMARY AND CONCLUSION
+
===Summary and Conclusion===
  
 
In our observations the first sign of the formation of angioblasts is shown in stage I, embryo A, in which neither the head fold nor the anlage of the pericardial cavity has yet appeared.
 
In our observations the first sign of the formation of angioblasts is shown in stage I, embryo A, in which neither the head fold nor the anlage of the pericardial cavity has yet appeared.
  
On the ventral surface of the mesoderm of the splanchnopleura of the cranial portion, cell bands first begin to separate, which separation is more advanced in the embryos B and C. These cell bands are regarded as angioblasts and they are frequently found to adhere to the indented and loosened mesoderm of the splanchnopleura by broader or narrower protoplasmic bridges. It has frequently been pointed -out that mitotic figures are found in the mesoderm of the splanchnopleura in the neighborhood of angioblasts. Furthermore, in many cases where the angioblasts are in close contact with the mesoderm of the splanchnopleura, it is impossible to discriminate the angioblasts from the mesodermal cells of the splanchnopleura, as concerns their sizes, forms, staining reaction, and the form of the nuclei, while a great difference can readily be recognized between the angio
+
On the ventral surface of the mesoderm of the splanchnopleura of the cranial portion, cell bands first begin to separate, which separation is more advanced in the embryos B and C. These cell bands are regarded as angioblasts and they are frequently found to adhere to the indented and loosened mesoderm of the splanchnopleura by broader or narrower protoplasmic bridges. It has frequently been pointed -out that mitotic figures are found in the mesoderm of the splanchnopleura in the neighborhood of angioblasts. Furthermore, in many cases where the angioblasts are in close contact with the mesoderm of the splanchnopleura, it is impossible to discriminate the angioblasts from the mesodermal cells of the splanchnopleura, as concerns their sizes, forms, staining reaction, and the form of the nuclei, while a great difference can readily be recognized between the angioblasts and the adjacent entodermal cells. These findings show that in the genetic origin the angioblasts for the future endocardium are derived directly from the mesoderm of the splanchnopleura. The origin of the angioblasts from the mesodermal cells continues until a later stage, in which the greater part of the endotheUal tubes are already differentiated from the angioblasts in the anterior portion of the embryo, but the origin of the angioblasts can be recognized in the posterior part of the embryo, as is shown in the embryo of stage III.
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 297
 
 
 
blasts and the adjacent entodermal cells. These findings show that in the genetic origin the angioblasts for the future endocardium are derived directly from the mesoderm of the splanchnopleura. The origin of the angioblasts from the mesodermal cells continues until a later stage, in which the greater part of the endotheUal tubes are already differentiated from the angioblasts in the anterior portion of the embryo, but the origin of the angioblasts can be recognized in the posterior part of the embryo, as is shown in the embryo of stage III.
 
  
 
In their well-known work on pericardial development, Strahl and Carius found it impossible to decide whether the embryonic coelom in the guinea pig appears at first in the region of the heart anlage, proceeding forward into the pericephahc mesoderm, or whether it begins first in the pericephalic mesoderm and then spreads out caudall}^ They speak as follows: Doch konnen wir augenblicklich eine ganz sichere Entscheidung nicht geben." The cause of this ambiguity is that they began their investigation of the origin of the intraembryonic coelom at too late a stage.
 
In their well-known work on pericardial development, Strahl and Carius found it impossible to decide whether the embryonic coelom in the guinea pig appears at first in the region of the heart anlage, proceeding forward into the pericephahc mesoderm, or whether it begins first in the pericephalic mesoderm and then spreads out caudall}^ They speak as follows: Doch konnen wir augenblicklich eine ganz sichere Entscheidung nicht geben." The cause of this ambiguity is that they began their investigation of the origin of the intraembryonic coelom at too late a stage.
Line 9,813: Line 9,553:
 
In our specimens, embryo C, stage I, show^s the discontinuous formation of the intraembryonic coelomic spaces in the cranial portion of the embryonic shield, as also in the pericephalic mesoderm, these spaces beginning as multiple foci. But they are primarily absent in the middle portion of the pericephalic mesoderm.
 
In our specimens, embryo C, stage I, show^s the discontinuous formation of the intraembryonic coelomic spaces in the cranial portion of the embryonic shield, as also in the pericephalic mesoderm, these spaces beginning as multiple foci. But they are primarily absent in the middle portion of the pericephalic mesoderm.
  
In stage II, in which the head fold of the embryo begins to separate from the surrounding blastoderm and the foregut has
+
In stage II, in which the head fold of the embryo begins to separate from the surrounding blastoderm and the foregut has just begun to develop, the intraembryonic coeloniic space spreads out cranially into the pericephaUc mesoderm, cleaving the mesodermal layer in such a way, that the lateral primitive pericardial cavities communicate with each other. In a just sHghtly younger embryonic shield than this, each lateral pericardial cavity has progressed cranially into the pericephalic mesoderm, showing in this place a sht-hke space, which however, is divided by a thin mesodermic bridge in the middle line.
 
 
 
 
 
 
298 TANZO YOSHINAGA
 
 
 
just begun to develop, the intraembryonic coeloniic space spreads out cranially into the pericephaUc mesoderm, cleaving the mesodermal layer in such a way, that the lateral primitive pericardial cavities communicate with each other. In a just sHghtly younger embryonic shield than this, each lateral pericardial cavity has progressed cranially into the pericephalic mesoderm, showing in this place a sht-hke space, which however, is divided by a thin mesodermic bridge in the middle line.
 
  
 
The pericardial cavity, therefore, commences simultaneously in the multiple foci, separating irregularly by mesodermal bridges throughout the lateral plate in the cranial portion of the embryonic shield and in the pericephalic mesoderm. These multiple coelemic spaces become confluent to form a single pericardial cavity, having an inverted-U shape, when the mesodermal bridges at the middle line of the pericephalic mesoderm have ultimately disappeared and, in consequence, at this time the bilateral pericardial cavities, already widely confluent, communicate from side to side (stage II, A). In this embryonic shield relatively wide endothelial tubes are differentiated only in the region of the hindbrain plate, where the pericardial cavity is wide open and the mesoderm of the splanchnopleura is thickened, projecting into the pericardial cavity as a prominent fold. In the pericephahc portion of the mesoderm, however, the pericardial cavity is seen merely as a lineal cleavage. Here a few angioblasts are scattered between the slightly thicker mesoderm of the splanchnopleura and the underlying entoderm.
 
The pericardial cavity, therefore, commences simultaneously in the multiple foci, separating irregularly by mesodermal bridges throughout the lateral plate in the cranial portion of the embryonic shield and in the pericephalic mesoderm. These multiple coelemic spaces become confluent to form a single pericardial cavity, having an inverted-U shape, when the mesodermal bridges at the middle line of the pericephalic mesoderm have ultimately disappeared and, in consequence, at this time the bilateral pericardial cavities, already widely confluent, communicate from side to side (stage II, A). In this embryonic shield relatively wide endothelial tubes are differentiated only in the region of the hindbrain plate, where the pericardial cavity is wide open and the mesoderm of the splanchnopleura is thickened, projecting into the pericardial cavity as a prominent fold. In the pericephahc portion of the mesoderm, however, the pericardial cavity is seen merely as a lineal cleavage. Here a few angioblasts are scattered between the slightly thicker mesoderm of the splanchnopleura and the underlying entoderm.
Line 9,825: Line 9,559:
 
In stage III the bilateral myocardial folds become quite prominent, so that in the region of the hindbrain plate they have been almost converted into the myocardial tubes, and enclose the well-developed endothelial tubes.
 
In stage III the bilateral myocardial folds become quite prominent, so that in the region of the hindbrain plate they have been almost converted into the myocardial tubes, and enclose the well-developed endothelial tubes.
  
The formation of these myocardial folds has progressed cranialward opposite to the foregut opening on the left side. At the same time the endothelial tube becomes gradually thinner cranialward and terminates slightly caudad to the foregut opening. On the right side the formation of the myocardial folds proceeds still farther cranially into the caudal part of the craniomedian Umb of the pericardial cavity, where the thicker mesoderm of
+
The formation of these myocardial folds has progressed cranialward opposite to the foregut opening on the left side. At the same time the endothelial tube becomes gradually thinner cranialward and terminates slightly caudad to the foregut opening. On the right side the formation of the myocardial folds proceeds still farther cranially into the caudal part of the craniomedian end of the pericardial cavity, where the thicker mesoderm of the splanchnopleura is raised from the underlying entoderm and in the space between them a number of angioblasts are distributed. On the right side the endothehal tube terminates cranially just opposite to the foregut opening. In front of the cranial termination of the lateral endothehal tubes a number of angioblasts are scattered, so that the cranial extremities of the endothehal tubes are nearly connected with each other through these angioblasts.
 
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 299
 
 
 
the splanchnopleura is raised from the underl3'ing entoderm and in the space between them a number of angioblasts are distributed. On the right side the endothehal tube terminates cranially just opposite to the foregut opening. In front of the cranial termination of the lateral endothehal tubes a number of angioblasts are scattered, so that the cranial extremities of the endothehal tubes are nearly connected with each other through these angioblasts.
 
  
 
The cranial extremities of the lateral myocardial folds have not yet come to complete confluence, as the mesoderm of the splanchnopleura, shghtly cephalad to the cranial extremity of the left myocardial fold, remains still in loose contact with the underlying entoderm. If this portion of the mesoderm of the splanchnopleura were completely raised from the underlying entoderm, forming the myocardial fold, then the myocardial anlagen would come into confluence.
 
The cranial extremities of the lateral myocardial folds have not yet come to complete confluence, as the mesoderm of the splanchnopleura, shghtly cephalad to the cranial extremity of the left myocardial fold, remains still in loose contact with the underlying entoderm. If this portion of the mesoderm of the splanchnopleura were completely raised from the underlying entoderm, forming the myocardial fold, then the myocardial anlagen would come into confluence.
  
The most prevalent opinions with regard to the mode of the formation of the unilateral myocardial heart anlage from the bilateral myocardial tubes agree that, as above described, the bilateral myocardial tubes, at first independently, come to actual fusion with each other, and then the septal wall between them is absorbed secondarily, thus forming a single myocardial cavity. Our specimens show that the formation of the myocardial folds does not occur synchronously throughout the pericardial cavity, as in the region of the hindbrain plate they first appeared and developed considerably, while in the craniomedian limb of the pericardial cavity the formation of the myocardial folds was just starting and rising slightly from the underlying entoderm. However, the communication of the lateral myocardial tubes is accomplished when the formation of the myocardial folds is completed in the craniomedian limb of the pericardial cavity, in which region the formation of these folds occurs last. For this reason, the cranial prolongation of the lateral myocardial tubes has not been brought about by the direct extension of the first part of the myocardial tubes, but by the continuous progressive differentiation into the craniomedian limb of the pericardial cavity. Therefore, the confluence of
+
The most prevalent opinions with regard to the mode of the formation of the unilateral myocardial heart anlage from the bilateral myocardial tubes agree that, as above described, the bilateral myocardial tubes, at first independently, come to actual fusion with each other, and then the septal wall between them is absorbed secondarily, thus forming a single myocardial cavity. Our specimens show that the formation of the myocardial folds does not occur synchronously throughout the pericardial cavity, as in the region of the hindbrain plate they first appeared and developed considerably, while in the craniomedian limb of the pericardial cavity the formation of the myocardial folds was just starting and rising slightly from the underlying entoderm. However, the communication of the lateral myocardial tubes is accomplished when the formation of the myocardial folds is completed in the craniomedian limb of the pericardial cavity, in which region the formation of these folds occurs last. For this reason, the cranial prolongation of the lateral myocardial tubes has not been brought about by the direct extension of the first part of the myocardial tubes, but by the continuous progressive differentiation into the craniomedian limb of the pericardial cavity. Therefore, the confluence of the myocardial tubes into a single myocardial cavity is not' accomplished by the actual fusion of the bilateral myocardial tubes, followed by absorption of the septal walls.
 
 
 
 
 
 
300 TANZO YOSHINAGA
 
 
 
the myocardial tubes into a single myocardial cavity is not' accomplished by the actual fusion of the bilateral myocardial tubes, followed by absorption of the septal walls.
 
  
 
In stage IV the formation of the myocardial fold is completely accomplished in the craniomedian limb of the pericardial cavity, elevating the mesoderm of the splanchnopleura from the underlying entoderm and projecting into the pericardial cavity. Both lateral myocardial tubes communicate with each other in this region.
 
In stage IV the formation of the myocardial fold is completely accomplished in the craniomedian limb of the pericardial cavity, elevating the mesoderm of the splanchnopleura from the underlying entoderm and projecting into the pericardial cavity. Both lateral myocardial tubes communicate with each other in this region.
Line 9,853: Line 9,575:
 
A number of workers declare that the lateral myocardial tubes are subdivided into many individual portions by the demarcations prior to the fusion of the lateral myocardial tubes; in the chick, Duval, '99; in the cat, IMartin, '02; in the rabbit, KoUiker, '84. Kolliker states, Ein Herz aus diesem Stadium ist sehr verschieden von dem primitiven Herzen eines Hlihnerembryo, was einfach darin begrundet ist, dass, wie bemerkt, bei Saugethieren schon vor der Verschmelzung der beiden Herzhiilften die drei Herzabschnitte angelegt sind."
 
A number of workers declare that the lateral myocardial tubes are subdivided into many individual portions by the demarcations prior to the fusion of the lateral myocardial tubes; in the chick, Duval, '99; in the cat, IMartin, '02; in the rabbit, KoUiker, '84. Kolliker states, Ein Herz aus diesem Stadium ist sehr verschieden von dem primitiven Herzen eines Hlihnerembryo, was einfach darin begrundet ist, dass, wie bemerkt, bei Saugethieren schon vor der Verschmelzung der beiden Herzhiilften die drei Herzabschnitte angelegt sind."
  
^lollier declares in similar language: 'Mn den beiden Herzrohren ist aber kurz vor ihrer Vereinigung schon eine Gliederung bemerkbar."
+
Kollier declares in similar language: 'Mn den beiden Herzrohren ist aber kurz vor ihrer Vereinigung schon eine Gliederung bemerkbar."
 
 
  
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 301
 
  
 
In our specimens this embryo shows first the atrioventricular constriction, even though in the previous embryo two myocardial tubes were already confluent into a single myocardial cavity.
 
In our specimens this embryo shows first the atrioventricular constriction, even though in the previous embryo two myocardial tubes were already confluent into a single myocardial cavity.
Line 9,868: Line 9,587:
  
 
Wang reports concerning a ferret embryo, having thirteen to fourteen somites, that the two endothelial tubes had united in a part of their extent. The fused portion, extending throughout about sixteen sections, appeared to be the ventricular part.
 
Wang reports concerning a ferret embryo, having thirteen to fourteen somites, that the two endothelial tubes had united in a part of their extent. The fused portion, extending throughout about sixteen sections, appeared to be the ventricular part.
 
THE ANATOMICAL RECORD, VOL. 21, NO. 3
 
 
 
 
302 TANZO YOSHINAGA
 
  
 
In our specimens this embryo shows first the fusion of the two lateral endothehal tubes throughout only seven sections, having a 5 /x thickness, and this united part corresponds to a middle third of the ventricle and lies precisely on the midsagittal plane. In the guinea pig the fusion of the lateral endothelial tubes takes place at a relatively early stage of development — a stage in which in the myocardial and endothelial tubes there can be distinguished simply the ventricular and atrial portions. In the above-mentioned animals investigated by other authors, the fusion of the lateral endothelial tubes was first noted in the relatively older embryo, in which the different parts of the myocardial and endothehal tubes are already definitely subdivided. JMoreover, their embryos show that the fused portion is considerably extended in comparison with this embrj^onic shield.
 
In our specimens this embryo shows first the fusion of the two lateral endothehal tubes throughout only seven sections, having a 5 /x thickness, and this united part corresponds to a middle third of the ventricle and lies precisely on the midsagittal plane. In the guinea pig the fusion of the lateral endothelial tubes takes place at a relatively early stage of development — a stage in which in the myocardial and endothelial tubes there can be distinguished simply the ventricular and atrial portions. In the above-mentioned animals investigated by other authors, the fusion of the lateral endothelial tubes was first noted in the relatively older embryo, in which the different parts of the myocardial and endothehal tubes are already definitely subdivided. JMoreover, their embryos show that the fused portion is considerably extended in comparison with this embrj^onic shield.
Line 9,879: Line 9,592:
 
The factors which are generally accepted as the cause of the loop formation of the endothelial tubes depend on the fact that the rate of growth of the two endothelial tubes exceeds that of the pleuropericardial cavity. Bonnet depicts a dog embryo in which the primary subdivision of the endothelial tubes into sinus venosus, atrium, and ventricle has occurred before they have fused to form a single myocardial cavit}'.
 
The factors which are generally accepted as the cause of the loop formation of the endothelial tubes depend on the fact that the rate of growth of the two endothelial tubes exceeds that of the pleuropericardial cavity. Bonnet depicts a dog embryo in which the primary subdivision of the endothelial tubes into sinus venosus, atrium, and ventricle has occurred before they have fused to form a single myocardial cavit}'.
  
W^ang pointed out the loop formation with the subdivision of the heart (atrium, ventricle, bulbus, etc.) in the ferret embryo, before the endothelial tubes had become fused.
+
Wang pointed out the loop formation with the subdivision of the heart (atrium, ventricle, bulbus, etc.) in the ferret embryo, before the endothelial tubes had become fused.
  
 
But in our specimens there is no loop formation, nor can the subdivision of the heart be marked out on either of the endothelial tubes before they are fused together, even though the ventricle and atrium may be roughl}^ distinguished by their difference in size.
 
But in our specimens there is no loop formation, nor can the subdivision of the heart be marked out on either of the endothelial tubes before they are fused together, even though the ventricle and atrium may be roughl}^ distinguished by their difference in size.
  
Contrary to the above-mentioned assumption that the loop formation of the endothelial tubes has been brought about, the moment of fusion of the two lateral endothehal tubes shows quite other facts in the guinea pig. In the embryonic shield at this stage of development the confluent part of the myocardial tube grows excessively in the craniocaudal direction and decreases its lateral width in comparison with the embryo of stage V, as measured and compared on both reconstruction
+
Contrary to the above-mentioned assumption that the loop formation of the endothelial tubes has been brought about, the moment of fusion of the two lateral endothehal tubes shows quite other facts in the guinea pig. In the embryonic shield at this stage of development the confluent part of the myocardial tube grows excessively in the craniocaudal direction and decreases its lateral width in comparison with the embryo of stage V, as measured and compared on both reconstruction models which had been magnified to the same degree. Consequently, the two endothehal tubes are brought together in the median plane, where they come to fusion, by the extreme longitudinal stretching of that part of the myocardial tube in which the endothelial tubes are enclosed. Concurrently, the active dilatation of the two endothelial tubes plays a part in bringing about the fusion, which takes place first in the most dilated portions.
 
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 303
 
 
 
models which had been magnified to the same degree. Consequently, the two endothehal tubes are brought together in the median plane, where they come to fusion, by the extreme longitudinal stretching of that part of the myocardial tube in which the endothelial tubes are enclosed. Concurrently, the active dilatation of the two endothelial tubes plays a part in bringing about the fusion, which takes place first in the most dilated portions.
 
  
 
In stage VII the myocardium presents cranially a single expanded craniomedian extremity, assuming a sac form, and here represents the ventricle, while caudally this myocardial sac is bifurcated into two rather slender myocardial prolongations. Their demarcation is indicated by the well-developed atrioventricular constriction sUghtly cephalad to the foregut opening. The transition from the atrium into the sinus venosus is marked by an indefinite indentation on the bilateral myocardial tubes caudad to the foregut opening and slightly more distinct on the left side. Corresponding to these myocardial constrictions, there can be pointed out a similar indentation on the endothelial tube on the left side.
 
In stage VII the myocardium presents cranially a single expanded craniomedian extremity, assuming a sac form, and here represents the ventricle, while caudally this myocardial sac is bifurcated into two rather slender myocardial prolongations. Their demarcation is indicated by the well-developed atrioventricular constriction sUghtly cephalad to the foregut opening. The transition from the atrium into the sinus venosus is marked by an indefinite indentation on the bilateral myocardial tubes caudad to the foregut opening and slightly more distinct on the left side. Corresponding to these myocardial constrictions, there can be pointed out a similar indentation on the endothelial tube on the left side.
Line 9,898: Line 9,605:
  
 
jMiss Parker describes the heart of the Perameles obesula stage V as follows: In the ventricular region of the heart, the right and left endothelial tubes are approximately equal in size, but where there is an inequality the right is the larger."
 
jMiss Parker describes the heart of the Perameles obesula stage V as follows: In the ventricular region of the heart, the right and left endothelial tubes are approximately equal in size, but where there is an inequality the right is the larger."
 
 
 
304 TANZO YOSHINAGA
 
  
 
In the ferret embryo Doctor Wang says: "It has been found that the two tubes, prior to fusion, appear to have been shifted as a whole toward the right side and that they remain in this position even after partial fusion has taken place.' '
 
In the ferret embryo Doctor Wang says: "It has been found that the two tubes, prior to fusion, appear to have been shifted as a whole toward the right side and that they remain in this position even after partial fusion has taken place.' '
Line 9,909: Line 9,612:
 
In stage VIII there are present three distinct constrictions on the tubular myocardial surface, infolding the whole thickness of the myocardial wall into the mj^oeardial csLvity. Consequently, the myocardium can be subdivided by very distinct demarcations into the bulbus cordis, bulboventricular constriction, ventricle, atrioventricular constriction, atrium, sino-atrial constriction, and sinus venosus in the craniocaudal succession.
 
In stage VIII there are present three distinct constrictions on the tubular myocardial surface, infolding the whole thickness of the myocardial wall into the mj^oeardial csLvity. Consequently, the myocardium can be subdivided by very distinct demarcations into the bulbus cordis, bulboventricular constriction, ventricle, atrioventricular constriction, atrium, sino-atrial constriction, and sinus venosus in the craniocaudal succession.
  
The bulbus cordis is demarcated from the dorsal wall of the expanded right ventricle at its cranial end by the horizontal bulboventricular constriction. The bulboventricular constriction shows considerable asymmetry, making a deeper furrow on the external surface of the mj^ocardium at the left and cranial sides, while at the right side it is present as a shallow depression on the external surface, diminishing imperceptibly caudalward, until it has entirely disappeared at the part of the right ventricle. Thus neither external furrow
+
The bulbus cordis is demarcated from the dorsal wall of the expanded right ventricle at its cranial end by the horizontal bulboventricular constriction. The bulboventricular constriction shows considerable asymmetry, making a deeper furrow on the external surface of the mj^ocardium at the left and cranial sides, while at the right side it is present as a shallow depression on the external surface, diminishing imperceptibly caudalward, until it has entirely disappeared at the part of the right ventricle. Thus neither external furrow nor infolding of the myocardium is shown along the caudal boundary of the bulboventricular junction, and here the wall of the bulbus is directly continuous into that of the right ventricle. Corresponding to the external view, the deep infolding of the myocardial wall as the inner prominent ridge is shown at the left and cranial sides of the bulboventricular canal, while on the right side it can be recognized only cranially and disappears insensibly caudalward. In this fashion the curvature of the myocardium at the bulboventricular junction is effected in such a vray that its convexity is turned toward the right side. On the dorsal aspect of the bulbus cordis there is a triangular intermesocardial space disposed vertically and sHghtly toward the left side, through which the truncus arteriosus passes out from the myocardial cavity up to the floor of the foregut.
 
 
 
 
 
 
EARLY DEVELOPMENT OF HEART IN MAMMALIA 305
 
 
 
nor infolding of the myocardium is shown along the caudal boundary of the bulboventricular junction, and here the wall of the bulbus is directly continuous into that of the right ventricle. Corresponding to the external view, the deep infolding of the myocardial wall as the inner prominent ridge is shown at the left and cranial sides of the bulboventricular canal, while on the right side it can be recognized only cranially and disappears insensibly caudalward. In this fashion the curvature of the myocardium at the bulboventricular junction is effected in such a vray that its convexity is turned toward the right side. On the dorsal aspect of the bulbus cordis there is a triangular intermesocardial space disposed vertically and sHghtly toward the left side, through which the truncus arteriosus passes out from the myocardial cavity up to the floor of the foregut.
 
  
 
The atrioventricular canal is well marked and is disposed approximately in the vertical plane. It is produced by the infolding of the myocardial wall, which is deeper and more caudad on the right side than on the left. Consequently, the opening of this canal is situated on the left side of the middle plane. In this relation the myocardial tube forms a marked curvature at the atrioventricular junction, turning its convexity toward the left side and ventralward, with the result that the ventricular portion lies at the right side and slightl}^ ventrally to the atrial portion. This curvature is remarkably accentuated in the next stage of the development, in which, for a short extent, the dorsal mesocardium disappears at the atrioventricular junction and herewith the ventricle comes to the ventral surface of the atrium, being free from the restriction of the dorsal mesocardium.
 
The atrioventricular canal is well marked and is disposed approximately in the vertical plane. It is produced by the infolding of the myocardial wall, which is deeper and more caudad on the right side than on the left. Consequently, the opening of this canal is situated on the left side of the middle plane. In this relation the myocardial tube forms a marked curvature at the atrioventricular junction, turning its convexity toward the left side and ventralward, with the result that the ventricular portion lies at the right side and slightl}^ ventrally to the atrial portion. This curvature is remarkably accentuated in the next stage of the development, in which, for a short extent, the dorsal mesocardium disappears at the atrioventricular junction and herewith the ventricle comes to the ventral surface of the atrium, being free from the restriction of the dorsal mesocardium.
Line 9,921: Line 9,618:
 
The ventricle can be divided incompletely into two hmbs by the ventral and dorsal longitudinal sulci. At the caudal part of the ventricle, for a short distance, the two hmbs are divided into two completely independent cavities by the septal wall. The caudal extremity of the right ventricle terminates bUndly as a conical process and it projects caudolaterally.
 
The ventricle can be divided incompletely into two hmbs by the ventral and dorsal longitudinal sulci. At the caudal part of the ventricle, for a short distance, the two hmbs are divided into two completely independent cavities by the septal wall. The caudal extremity of the right ventricle terminates bUndly as a conical process and it projects caudolaterally.
  
 
 
306 TANZO YOSHINAGA
 
  
 
In the literature I could not find a description of this. On first observation it seemed to me that the septal wall and its conversion into prominent ridges at the inner surface of the ventral and dorsal myocardial wall were produced by the actual fusion of the two lateral myocardial tubes. Therefore, this may account for the remnant of the primitive myocardial septum. But in the embryos of stages VI and VII there was present no septal wall nor prominent ridge similar to this in their single ventricle, in which they would be more distinctly present if they accounted for the production of the actual fusion of the lateral myocardial tubes and the remnant of the primitive cardiac septum.
 
In the literature I could not find a description of this. On first observation it seemed to me that the septal wall and its conversion into prominent ridges at the inner surface of the ventral and dorsal myocardial wall were produced by the actual fusion of the two lateral myocardial tubes. Therefore, this may account for the remnant of the primitive myocardial septum. But in the embryos of stages VI and VII there was present no septal wall nor prominent ridge similar to this in their single ventricle, in which they would be more distinctly present if they accounted for the production of the actual fusion of the lateral myocardial tubes and the remnant of the primitive cardiac septum.
Line 9,929: Line 9,623:
 
Accordingly, it appears to be due to the fact that the caudal surface of the myocardial ventricle on the right side is projected actively backward by the unequally excessive rate of growth in this portion, while in the middle plane a part of the myocardial wall does not proportionately accompany this active backward growth, but remains as the septal wall.
 
Accordingly, it appears to be due to the fact that the caudal surface of the myocardial ventricle on the right side is projected actively backward by the unequally excessive rate of growth in this portion, while in the middle plane a part of the myocardial wall does not proportionately accompany this active backward growth, but remains as the septal wall.
  
LITERATURE CITED
+
===Literature Cited===
 
 
Arky 1917 A laboratory manual and textbook of embryology. Philadelphia
 
 
 
and London. Atwell 1915 On the conversion of a photograph into a line drawing. Anat.
 
 
 
Rec, vol. 10, p. 39. Balfour 1881 A treatise on comparative embryology, vol. 2, London. BiscHOFF 1852 Entwickelungsgcschichte des Meerschweinchens. Giessen. Bonnet 1884 Beitrage zur Embryologie der Wiederkauer, genommen am
 
 
 
Shafei. Arch. f. Anat. u. Physiol. Anat. Ab. P. 1. Jahrg. 1889 a. P.
 
 
 
170 Jahrg.
 
 
 
1901 Beitrage zur Embryologie des Hundes. Anat. Heft., Bd. 16,
 
 
 
S. 233.
 
 
 
1889 Beitrage zur Entwickelungsgeschichte des Saugethiereherzens.
 
 
 
Arch. f. Mik. Anat., Bd. 33, S. 284.
 
 
 
1900 Rekonstruktionsmethoden. Taschenbuch der Mikroskopischen
 
 
 
Technik. Miinchen. Bremer 1912 The development of the aorta and aortic arches in rabbits.
 
 
 
Am. Jour. Anat., vol. 13, p. 111. Dandy 1910 A human embryo with seven pairs of somites measuring about
 
 
 
2 mm. in length. Am. Jour. Anat., vol. 10, p. 86. EvAN.s 1909 On the development of the arotae, cardinal and umbilical veins
 
 
 
and the other blood vessels of vertebrate embryos from capillaries.
 
 
 
Anat. Rec, vol. 3, p. 498.
 
 
 
 
 
 
 
E.\ELY DEVELOPMENT OF HEART IN MAMMALIA 307
 
 
 
Graper 1912 Beobachtung von Wachstumvorgangen an Reiheaufnahmen
 
 
 
lebender Hiihnerembryonen nebst Bemerkungen iiber vitale Farbung.
 
 
 
Arch. f. Entwickel. d. Organ., Bd. 33, S. 330. Hahn 1909 Experimentelle Studien tiber die Entstehung des Blutes und der
 
 
 
ersten Gefasse beim Hiihnchen. Arch. f. Entwickelungsmecha. d.
 
 
 
Organ., Bd. 27, S. 337. Hensen 1875-1S76 Beobachtungen liber die Befruchtung und Entwickelung
 
 
 
des Kaninchen und Meerschweinchens. Zeitschrift f. Anat. u. Entwickel. Bd. 1, S. 213-353. Hertwig, O. 1910 Lehrbuch der Entwickelungsgeschichte des Menschen und
 
 
 
der Wirbelthiere. Jena. His 1880 Anatomie menschlicher Embryonen. Leipzig.
 
 
 
1881 Mittheilung zur Embryologie der Saugethiere und des Menschen.
 
 
 
Arch. f. Anat. u. Entwickel., S. 303.
 
 
 
1886 Beitrage zur Anatomie des menschlichen Herzens. Leipzig.
 
 
 
1901 Lecithoblast und Angioblast der Wirbelthiere. Abhandlungen
 
 
 
der jMathematisch-physischen Classe der Konigslich Sachsischen
 
 
 
Gesellschaft der Wissenschaften, Bd. 26, S. 173. Leipzig. HuBER 1918 On the anlage and morphogenesis of the chorda dorsalis in mammalia, in particular the guinea pig (Cavis cobaya). Anat. Rec, vol.
 
 
 
14, p. 217. Keibel 1896 Studien zur Entwickelungsgeschichte des Schw^eines. Mor phologische Arbeiten, Bd. 5, S. 1. KoLLiKER 1861-1879 Entwickelungsgeschichte des Menschen und der hoheren
 
 
 
Thiere. Leipzig.
 
  
1884 Grundriss der Entwickelungsgeschichte des Menschen und der
+
Arky 1917 A laboratory manual and textbook of embryology. Philadelphia and London. Atwell 1915 On the conversion of a photograph into a line drawing. Anat. Rec, vol. 10, p. 39.
  
hoheren Thiere. Leipzig. Lewis 1903 The intraembryonic blood vessels of rabbits from 8i to 13 days.
+
Balfour 1881 A treatise on comparative embryology, vol. 2, London.  
  
Proceedings of the Association of American Anatomists. Am. Jour.
+
BiscHOFF 1852 Entwickelungsgcschichte des Meerschweinchens. Giessen.  
  
Anat., vol. 3, p. 12. Mall 1912 On the development of the human heart. Am. Jour.
+
Bonnet 1884 Beitrage zur Embryologie der Wiederkauer, genommen am Shafei. Arch. f. Anat. u. Physiol. Anat. Ab. P. 1. Jahrg. 1889 a. P. 170 Jahrg.
  
Anat., vol. 13, p. 249. Martin 1902 Die Ontogenie der Haustiere. Lehrbuch d. Anat. d. Haustiere.
+
1901 Beitrage zur Embryologie des Hundes. Anat. Heft., Bd. 16, S. 233.
  
Bd. 1, S. 23. Stuttgart. Miller and McWhorter 1914 Experiments on the development of blood vessels in the area pellucida and embryonic body of the chick. Anat.
+
1889 Beitrage zur Entwickelungsgeschichte des Saugethiereherzens. Arch. f. Mik. Anat., Bd. 33, S. 284.
  
Rec, vol. 8, p. 203. MixoT 1892 Human embrj-ology. New York. Parker 1915 The early development of the heart and anterior vessels in
+
1900 Rekonstruktionsmethoden. Taschenbuch der Mikroskopischen Technik. Miinchen.  
  
marsupials, with special reference to Perameles. Proceedings of the
+
Bremer 1912 The development of the aorta and aortic arches in rabbits. Am. Jour. Anat., vol. 13, p. 111.  
  
General Meetings for Scientific Business of the Zoological Society of
+
Dandy 1910 A human embryo with seven pairs of somites measuring about 2 mm. in length. Am. Jour. Anat., vol. 10, p. 86.
  
London, p. 459. Rabl 1887 Ueber die Bildung der Herzens er Amphibien. Morphol. Jahrb.,
+
EvANs 1909 On the development of the arotae, cardinal and umbilical veins and the other blood vessels of vertebrate embryos from capillaries. Anat. Rec, vol. 3, p. 498.
  
Bd. 12, S. 252.
+
Graper 1912 Beobachtung von Wachstumvorgangen an Reiheaufnahmen lebender Hiihnerembryonen nebst Bemerkungen iiber vitale Farbung.
 +
Arch. f. Entwickel. d. Organ., Bd. 33, S. 330.  
  
1889 Theorie des ^Mesoderms. Morphol. Jahrb., Bd. 15, S. 113. Ravn 1889 Ueber die Bildung der Scheidewand zwischen Brust und Bauch hohle in Saugethierembryonen. Arch. f. Anat. u. Entwickel., S. 123.
+
Hahn 1909 Experimentelle Studien tiber die Entstehung des Blutes und der ersten Gefasse beim Hiihnchen. Arch. f. Entwickelungsmecha. d. Organ., Bd. 27, S. 337.  
  
1895 Ueber das Proamnion, besonders bei der Maus. .\rch. f . .\nat. u.
+
Hensen 1875-1S76 Beobachtungen liber die Befruchtung und Entwickelung des Kaninchen und Meerschweinchens. Zeitschrift f. Anat. u. Entwickel. Bd. 1, S. 213-353.  
  
Entwickel., S. 189.
+
Hertwig, O. 1910 Lehrbuch der Entwickelungsgeschichte des Menschen und der Wirbelthiere. Jena.  
  
 +
His 1880 Anatomie menschlicher Embryonen. Leipzig. 1881 Mittheilung zur Embryologie der Saugethiere und des Menschen. Arch. f. Anat. u. Entwickel., S. 303. 1886 Beitrage zur Anatomie des menschlichen Herzens. Leipzig. 1901 Lecithoblast und Angioblast der Wirbelthiere. Abhandlungen der jMathematisch-physischen Classe der Konigslich Sachsischen Gesellschaft der Wissenschaften, Bd. 26, S. 173. Leipzig.
  
 +
HuBER 1918 On the anlage and morphogenesis of the chorda dorsalis in mammalia, in particular the guinea pig (Cavis cobaya). Anat. Rec, vol. 14, p. 217.
  
308 TANZO YO SHI NAG A
+
Keibel 1896 Studien zur Entwickelungsgeschichte des Schw^eines. Mor phologische Arbeiten, Bd. 5, S. 1. KoLLiKER 1861-1879 Entwickelungsgeschichte des Menschen und der hoheren Thiere. Leipzig.
  
Reagan 1915 Vascularization phenomena in fragments of embryonic bodies
+
1884 Grundriss der Entwickelungsgeschichte des Menschen und der hoheren Thiere. Leipzig. Lewis 1903 The intraembryonic blood vessels of rabbits from 8i to 13 days. Proceedings of the Association of American Anatomists. Am. Jour. Anat., vol. 3, p. 12.
  
completely isolated from yolk sac blastoderm. Anat. Rec, vol. 9,
+
Mall 1912 On the development of the human heart. Am. Jour. Anat., vol. 13, p. 249. Martin 1902 Die Ontogenie der Haustiere. Lehrbuch d. Anat. d. Haustiere. Bd. 1, S. 23. Stuttgart.
  
p. 328. Robinson 1892 Observation upon the development of the segmentation cavity,
+
Miller and McWhorter 1914 Experiments on the development of blood vessels in the area pellucida and embryonic body of the chick. Anat. Rec, vol. 8, p. 203.
  
the archenteron, the germinal layers, and the amnion in mammals.
+
MinoT 1892 Human embryology. New York. Parker 1915 The early development of the heart and anterior vessels in marsupials, with special reference to Perameles. Proceedings of the General Meetings for Scientific Business of the Zoological Society of London, p. 459.  
  
Quarterly Journal of Microsc. Sci., vol. 33, Op. 369.
+
Rabl 1887 Ueber die Bildung der Herzens er Amphibien. Morphol. Jahrb., Bd. 12, S. 252. 1889 Theorie des ^Mesoderms. Morphol. Jahrb., Bd. 15, S. 113.  
  
1903 The early stages of the development of the pericardium. Journal of Anat. a. Physiol., vol. 37, p. 1. Rose 1889 Zur Entwickelungsgeschichte des Saugethierherzens. Morphol.
+
Ravn 1889 Ueber die Bildung der Scheidewand zwischen Brust und Bauch hohle in Saugethierembryonen. Arch. f. Anat. u. Entwickel., S. 123. 1895 Ueber das Proamnion, besonders bei der Maus. Arch. f . Anat. u. Entwickel., S. 189.
  
Jahrb., Bd. 15, S. 436.
 
  
1890 Beitrage zur vergleichenden Anatomie des Herzens der Wirbel thiere. Morphol. Jahrb., Bd. 16, S. 27. RouviERE 1904 Etude sur le developpement du pericarde chez le lapin. Jour.
+
Reagan 1915 Vascularization phenomena in fragments of embryonic bodies completely isolated from yolk sac blastoderm. Anat. Rec, vol. 9, p. 328.  
  
de I'Anatomie et de la Physiologie, p. 610. RucKERT UND MoLLiER 1906 Die erste Entstehung der Gefasse und des Blutes
+
Robinson 1892 Observation upon the development of the segmentation cavity, the archenteron, the germinal layers, and the amnion in mammals. Quarterly Journal of Microsc. Sci., vol. 33, Op. 369.
  
bei Wirbeltieren. Handbuch der vergleichenden und experimentellen
+
1903 The early stages of the development of the pericardium. Journal of Anat. a. Physiol., vol. 37, p. 1. Rose 1889 Zur Entwickelungsgeschichte des Saugethierherzens. Morphol. Jahrb., Bd. 15, S. 436.
  
Entwickelungslehre der Wirbeltiere. Jena. ScHULTZE 1914 Early stages of vasculogehesis in the cat (Felis domestica)
+
1890 Beitrage zur vergleichenden Anatomie des Herzens der Wirbel thiere. Morphol. Jahrb., Bd. 16, S. 27.  
  
with special reference to the mesenchymal origin of the endothelium.
+
RouviERE 1904 Etude sur le developpement du pericarde chez le lapin. Jour. de I'Anatomie et de la Physiologie, p. 610.  
  
Memoirs of the Wistar Institute of Anatomy and Biology, no. 3.
+
RucKERT UND MoLLiER 1906 Die erste Entstehung der Gefasse und des Blutes bei Wirbeltieren. Handbuch der vergleichenden und experimentellen Entwickelungslehre der Wirbeltiere. Jena.  
  
1915-16 The fusion of the bilateral anlagen of the heart and the formation of the bulbo-ventricular loop in embryo of the cat. Anat. Rec,
+
ScHULTZE 1914 Early stages of vasculogehesis in the cat (Felis domestica) with special reference to the mesenchymal origin of the endothelium. Memoirs of the Wistar Institute of Anatomy and Biology, no. 3. 1915-16 The fusion of the bilateral anlagen of the heart and the formation of the bulbo-ventricular loop in embryo of the cat. Anat. Rec, vol. 10, p. 242.
  
vol. 10, p. 242. Selenka 1883-1892 Studien iiber die Entwickelungsgeschichte der Thiere,
+
Selenka 1883-1892 Studien iiber die Entwickelungsgeschichte der Thiere, 1-5 H. Wiesbaden. Sobatta 1902 Ueber Entwickelung des Blutes, des Herzens und der grossen Gefassstilmme der Salmoniden nebst Mittcilungen liber die Ausbildung der Herzform. Anat. Heft., Bd. 19, S. 579.
  
1-5 H. Wiesbaden. Sobatta 1902 Ueber Entwickelung des Blutes, des Herzens und der grossen
+
Spee 1889 Beobachtungen an einer menschlichen Keimscheibe mit offener Medullarrinne und Canalis neurcntericus. Arch. f. Anat. u. Ent wickel., S. 159.
  
Gefassstilmme der Salmoniden nebst Mittcilungen liber die Ausbildung
+
Strahl und Carius 1S89 Beitrage zur Entwickelungsgeschichte des Herzens und der Korperhohlen. Arch. f. Anat. u. Entwickel., S. 231.
  
der Herzform. Anat. Heft., Bd. 19, S. 579. Spee 1889 Beobachtungen an einer menschlichen Keimscheibe mit offener
+
UsKOW 1883 Ueber die Entwickelung des Zwerchfells, des Pericarduims und des Coeloms. Arch. f. mik. Anat., Bd. 22, S. 143.  
  
Medullarrinne und Canalis neurcntericus. Arch. f. Anat. u. Ent wickel., S. 159. Strahl und Carius 1S89 Beitrage zur Entwickelungsgeschichte des Herzens
+
Wang 1917 The earliest stages of development of the blood vessels and of the heart of the ferret embryo. Jour, of Anat., vol. 3, p. 107.  
  
und der Korperhohlen. Arch. f. Anat. u. Entwickel., S. 231. UsKOW 1883 Ueber die Entwickelung des Zwerchfells, des Pericarduims und
+
Wilson 1914 Observations upon young human embryos. Jour, of Anat. and Physiol., vol. 48, p. 315.  
  
des Coeloms. Arch. f. mik. Anat., Bd. 22, S. 143. Wang 1917 The earliest stages of development of the blood vessels and of the
+
Yeates 1915 Studies in the embryology of the ferret. Studies in anatomy from the Anatomical Department of the University of Birmingham, p. 71.  
  
heart of the ferret embryo. Jour, of Anat., vol. 3, p. 107. Wilson 1914 Observations upon young human embryos. Jour, of Anat. and
+
Yoshinaga 1920 Beitrage zur Streitfragen iiber den Ursprung der Gefass zellen bei den Amphibien. Acta Scholae Medicinalis Universitatis Imperial is in Kioto, vol. 3.
 
 
Physiol., vol. 48, p. 315. Yeates 1915 Studies in the embryology of the ferret. Studies in anatomy
 
 
 
from the Anatomical Department of the University of Birmingham,
 
 
 
p. 71. Yoshinaga 1920 Beitrage zur Streitfragen iiber den Ursprung der Gefass zellen bei den Amphibien. Acta Scholae Medicinalis Universitatis
 
 
 
Imperial is in Kioto, vol. 3.
 
  
  
Line 10,095: Line 9,719:
 
5T the bibliographic SERVICE, MAT 23
 
5T the bibliographic SERVICE, MAT 23
  
 +
==Abnoraial Position Of The Duodenum==
  
 
+
James W. Papez
ABNORAIAL POSITION OF THE DUODENUM
 
 
 
JAMES W. PAPEZ
 
  
 
Department of Anatomy, Cornell University Medical School, Ithaca, Neiv York
 
Department of Anatomy, Cornell University Medical School, Ithaca, Neiv York
  
SEVEN FIGURES (tWO PLATES)
+
Seven Figures (Two Plates)
  
 
This case is reported because it shows a rare malposition of the duodenum and is an example of incomplete rotation of this organ around the mesenteric pedicle. There are not many cases of malposition of the duodenum on record. The surgical importance of these anomalies is indicated in the case reported by Mumford ('06) and that reported by Freeman ('20). These cases are of interest because they can be explained on the basis of arrest or variation in the normal developmental processes in that region.
 
This case is reported because it shows a rare malposition of the duodenum and is an example of incomplete rotation of this organ around the mesenteric pedicle. There are not many cases of malposition of the duodenum on record. The surgical importance of these anomalies is indicated in the case reported by Mumford ('06) and that reported by Freeman ('20). These cases are of interest because they can be explained on the basis of arrest or variation in the normal developmental processes in that region.
Line 10,110: Line 9,732:
  
 
Meckel, in 1917, and His, in 1885, estabhshed the development of the intestinal canal. Mall ('97) has demonstrated how the coils of the intestine develop and the position which they ultimately assume. A comprehensive study of the subject is given by Lewis ('12). Lewis and Papez, in a series of reconstructions designed to show the development of the mesentery, demonstrated how the duodenum rotates around the mesenteric pedicle in young human embryos. More recently, Frazier ('19) has figured a series of reconstructions to show the formation of the duodenal curve, and Vogt ('20) has figured the duodenum and structures in the mesenteric pedicle in human embryos 12.5, 22, and 33 mm. long.
 
Meckel, in 1917, and His, in 1885, estabhshed the development of the intestinal canal. Mall ('97) has demonstrated how the coils of the intestine develop and the position which they ultimately assume. A comprehensive study of the subject is given by Lewis ('12). Lewis and Papez, in a series of reconstructions designed to show the development of the mesentery, demonstrated how the duodenum rotates around the mesenteric pedicle in young human embryos. More recently, Frazier ('19) has figured a series of reconstructions to show the formation of the duodenal curve, and Vogt ('20) has figured the duodenum and structures in the mesenteric pedicle in human embryos 12.5, 22, and 33 mm. long.
 
309
 
 
 
 
310 JAMES W. PAPEZ
 
  
 
Several embryonic structures shape the duodenal curve. In the young human embryo the mesenteric pedicle is formed dorsal to the gastroduodenal region by the primitive portal anastomosis, the pancreas, and the roots of the mesenteric vessels. At an early stage (5 mm.) the primitive portal anastomosis, the proximal ends of the vitelline vessels, and the hepatic bud form the conspicuous features in this region. Soon, however, the growing pancreas invades this area of the mesentery and forms a constant and prominent mass around the roots of the great mesenteric vessels. It is over the right side of this pedicle that the curve of the duodenum is begun, and is subsequently completed by passing around its dorsal side. Complete rotation of the duodenum is normally concomitant with the rotation of the general mesentery, as shown in a 42-mm. embryo by Papez and Lewis ('17) and in a 40-mm. embryo by Frazier ('19).
 
Several embryonic structures shape the duodenal curve. In the young human embryo the mesenteric pedicle is formed dorsal to the gastroduodenal region by the primitive portal anastomosis, the pancreas, and the roots of the mesenteric vessels. At an early stage (5 mm.) the primitive portal anastomosis, the proximal ends of the vitelline vessels, and the hepatic bud form the conspicuous features in this region. Soon, however, the growing pancreas invades this area of the mesentery and forms a constant and prominent mass around the roots of the great mesenteric vessels. It is over the right side of this pedicle that the curve of the duodenum is begun, and is subsequently completed by passing around its dorsal side. Complete rotation of the duodenum is normally concomitant with the rotation of the general mesentery, as shown in a 42-mm. embryo by Papez and Lewis ('17) and in a 40-mm. embryo by Frazier ('19).
Line 14,531: Line 14,147:
  
 
Translation by Jos6 F. Nonidez Cornell Medical College, New York
 
Translation by Jos6 F. Nonidez Cornell Medical College, New York
 
 
  
 
==A microscopical study of the sinoventricular bundle of the rabbit's heart==
 
==A microscopical study of the sinoventricular bundle of the rabbit's heart==

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THE ANATOMICAL RECORD

EDITOR JOHN LEWIS BREMER

Harvard Medical School

VOLUME 21 APRIL — JULY, 1921

PHILADELPHIA

THE WISTAR INSTITUTE OF ANATOMY AND BIOLOGY


Contents

NO. 1. APRIL

C. B. Moore. Infections in the female urethra. Ten figures 1

Richard E. Scammon. A simple tracing apparatus for making topographic reconstructions. Three figures ig

Richard E. Scammon. A note on the relation between the weight of the thyroid and the weight of the thymus in man 25

George B. Wislocki. Observations upon the behavior of carbon granules injected into pregnant animals 29

Proceedings of the American Association of Anatomists. Thirty-seventh session 35

Proceedings of the American Association of Anatomists. Abstracts 43

Proceedings of the American Association of Anatomists. Demonstrations 88

American Association of Anatomists. Constitution 92

American Association of Anatomists. Officers and list of members 95

NO. 2. MAY

George L. Streeter. Migration of the ear vesicle in the tadpole during normal development. Eleven figures 115

Eleanor Linton Clark and Eliot R. Clark. The character of the lymphatics in experimental edema. Five figures 127

S.E. Whitnall. Some abnormal muscles of the orbit. Twofigures 143

H. E. Radasch. The determination of thepercentage of the organic content of compact bone 153

Eben J. Carey. Studies on the structure and function of the small intestine. Twentytwo figures 189

Naohide Yatsu. On the changes in the reproductive organs in heterosexual parabiosis of albino rats. Seven figures 217

Howard H. Bell. Diverticula of the duodenum. Two figures 292

NO. 3. JUNE

Tanzo Yoshinaga. A contribution to the early development of the heart in mammalia, with special reference to the guinea-pig. Twenty-three figures 239

James W. Papez. Abnormal position of the duodenum. Seven figures (two plates). 309

W. M. Baldwin. A study on the depth of penetration of ultraviolet light-ray energy in the embryo of the tadpole 323

E. Blankfein. An example of dissociation of the branches of the a. profunda fcmoris. One figure 329

Z. P. Metcalf. Some laboratory notes. Three figures 331

NO. 4. JULY

Juan C. XaSJagas. On the patency of the foramen ovale in Filipino newborn children. Three figures 339

Sabas E. Yap. Musculus sternalis in Filipinos. Two plates (ten figures) 353

Chas. W. Metz. a simple method for handling small objects in making microscopic preparations 373

Lee D. Cady. A microscopical study of the sinoventricular bundle of the rabbit's heart ; with reference to the data relative to its functional interpretation, especially in terms of a source of replacement of degenerated myocardium. One plate (five figures) 37.5

R. Bennett Bean. Remarks on teaching anatomy 391


With the commencement of the present volume (April) of The Anatomical Record a change has been made in the editorial management. At the recent meeting of the American Association of Anatomists a committee was elected to appoint editors for the two journals of the society, and to serve as an advisory committee for those so appointed. In the case of The A natomical Record the choice fell on me, and it was decided that I should assume the duties of editor at once. Although given the privilege of selecting one or more associate editors, I have decided not to do so for the present, at least, trusting that fellow members of the society will be willing occasionally to give me the benefit of their opinions of certain articles quite informally.

The policy of the journal will not be materially changed, but an attempt will be made to hasten the publication of accepted articles, to adhere a little more closely to the original plan of The Record, and to differentiate it more clearlj'- from The American Journal of Anatomy.

In order to accomplish these results, it will be necessary to limit the length of the articles printed. No definite rules can be laid down, but in the opinion of the advisory committee papers of five or ten printed pages will usually be much more acceptable than those necessitating greater elaboration; while notes on laboratory methods, preliminar}^ reports, etc., will be considered appropriate subject matter. All contributors are earnestly and confidently requested to cooperate in this policy.

At this time there are many articles alread}^ accepted by the former editorial board of The Record and ready for publication. These wdll, of course, be given precedence over later contributions. I have no hesitation in assuming their value, appreciating as I do, and as, I am sure, do all the readers of The Record, the careful and efficient work and the scientific discrimination of the former managing editor and his associates.

JOHN LEWIS BREMER.

All contributions and correspondence should be sent to J. L. Bremer, Harvard Medical School, Boston, Mass.


Resumen por el autor, C. B. ]Moore, Leland Stanford Junior University.

Infecciones do la uretra femcnina.

A causa de su estructura, posicion y niecanismo de desplazaniiento, la uretra femenina es muy propensa a la invasion bacterial. En ella se han encontrado una gran variedad de organismos. El gonococcus es el mas importante, por su tendencia hacia la cronicidad y sus efectos nocivos. En las glandulas para-uret rales de Skene pueden presentarse infecciones supurativas cronicas, y tambien en las estructuras vestigiales de la glandula prostatica, las cuales emiten pequefias cantidades de pus de modo indefinido en la uretra anterior, sin que exista ningun sintoma local, por cuya causa no se descubren frecuentemente. La destrucci6n completa de estas glandulas, tal como puede conseguirse niediante el electro-cauterio, parece ser el unico tratamiento f[ue puede terminar de modo pcrmanente las afecciones de dichas partes.

Translation by Jos6 F. Xonidez Cornell Medical College, New York

Infections In The Female Urethra

C. B. MOORE

Division of Obstetrics and Gynecology, Stanford School of Medicine, San Francisco

TEN FIGURES

In order to understand better the infections which occur in the female urethra and especially their tendency often to chronicity and the frequency with which they escape detection, a clinical and laboratory study of female urethras has been made during the last three years, together with a review of some of the literature which might be of assistance. The work in the laboratory comprises some bacteriological investigations and histological examinations of urethras of the newborn, infants, and adults of different ages. For the clinical studies, which were done at the same time in the Women's Clinic of the Stanford University School of Medicine, a new instrument was devised which has proved very satisfactory for the purpose of examinmg and treating the anterior urethra. Photographs of the microscopic sections and the instrument are appended below.

Because of its structure and location, the female urethra is very prone to bacterial invasion and retention, and for this reason is of distinct clinical interest both to the obstetrician and to the gynecologist. Infections occur here to a great extent only during the child-bearing period and it is not an unconnnon focus of infection during pregnancy.

The female urethra is a fibromuscular structure about 35 nun. in length, lying dorsally to the symphysis pubis and \Tntrally to the distal end of the anterior vaginal wall with which it is intimately associated. It is composed mostly of involuntary muscle fibers interwoven loosely with white fibrous and elastic tissue carrying numerous nerves and blood-ve§sels in its meshes, the corpus spongiosum. External to this appears two definite

1


2 C. B. MOORE

muscular coats, the inner, or longitudinal, and the outer, or circular coat. The latter forms a large ring, the unstriped sphincter, in the region of the vesicular neck; its reinforcement with striped muscle makes the striped or voluntary sphincter. The mucosa lining the canal is stratified squamous epithelium to a varying extent in the anterior end, stratified columnar epithelium in the intermediate region, and a transitional variety in the posterior end near the l^ladder. At the meatus of some subjects, especially nulliparous ones, the mucosa is extended into two lateral folds, called by Kelly (1) the labia urethrae. They vary in size and shape and undoubtedly assist in protecting the urethra from bacterial invasion from without. The urethral meatus usually lies about 10 mm. from the anterior vaginal wall. In some subjects it lies even closer than this, sometimes a few millimeters. In the mechanism described below the meatus may come even to lie in a plane with the anterior vaginal wall.

The most important feature of the mucosa and the one giving rise to most, if not all, of the pathology is the glands, the most important ones of which are those of Skene. There are also many mucous or sinus glands found throughout its course. The latter structures are lined with short colunmar epithelium and aie sometimes called Littre glands. Skene's glands, usually two in number, lie beneath the nmcosa posteriorly and near the meatus. They are individual, anatomic structures different from the crypts or sinus glands. Doctor Skene (2), of Brooklyn, in 1880, was the first one to discover these structures and realize their importance and to investigate their anatomy and some of their pathology. Dr. J. Kocks (3), of Bonn, and Prof. Max Schtiller (4), a couple of years later, also investigated and described these para-urethral glands. The former considered them vestigial structures of the wollfian tubules.

These glands have their genesis in the prostate which is present in both sexes (5). The first anlage of the prostate in the female appears in embryos of 50 mm.; in the male of 55 mm. At first the prostate consists of solid epithelial buds which extend into the suirounding mescnchyirre from the epithelium of the urogenital sinus, an early anterior division of the cloaca. Part of


INFECTIONS IN THE FEMALE URETHRA 3

the anterior division of the cloaca goes to make the l)la(kler and the urethra. These buds are most numerous on the dorsal surface, less so on the sides, and rarely on the ventral surface, although the}^ may at times appear aiound the whole periphery. Those on the dorsal surface develop and branch, while those on the ventral surface remain simple and mostly degenerate. In the male these buds become enveloped in a fibromuscular mass to make the prostate gland. Some of the ducts which were not included in the formation of the prostate gland form accessory glands. According to Keibel and ]\Iall, in the female embryo few glands are formed, three being the maximum number. These may undergo development and form the above-mentioned Skene's glands or ducts. This condition may possibly explain the different degrees of urethral infections in the female, at least to some extent. Since the glands are under retrogressive influences, the}^ may not appear in some cases; in others they ma}' be simple and shallow, in which case the infection is near the surface and therefore more easil}^ cured; in others they may attain greater development, in which case infections become deep-seated and with poor drainage. This latter type leads to the chronic case described below which has been so difficult to cure.

In the embryo there are still other glands which de^'elop in this region. These are the small sinus glands. They appear around the entire periphery of the urogenital sinus in the embryo of 60 mm. These glands have the character of those of Bartholin, but do not attain to the same development. The gland of Bartholin, also developed from the urogenital sinus, comes to lie outside of the urethra, for which reason it does not enter into the present topic. Thus it is revealed from embryonic studies that there is considerable glandular development in this region. According to the distribution of these glands, the urethra is sometimes divided into an anterior and a posterior urethra, the former being the glandular region and the latter the nonglandular region (6) .

The structure of Skene's para-urethral glands is described as follows (7): Upon each side, near the floor of the urethra, are


C. B. MOORE


two tubules extending from the vicinity of the meatus for 7 mm. to 15 mm. beneath the mucosa. The mouths of these tubes open upon the surface usually on either side of the median line about 3 nmi. from the outer border of the meatus. The upper ends of the tubules terminate in a number of di\'isions which branch off into the muscular walls of the urethra. These racemose structures are lined by a compound epithelium composed of three layers. The deepest layer is composed of young roundish cells having large, granular nuclei which make up the major portion of the cells. Next above this is a layer of cells of a somewhat spindle shape with prominent nuclei. They are young cells at a more advanced stage than those of the first layer. The next, or outermost, layer is composed of fully de\'eloped columnar epithelium with distinct nuclei arranged at the base of the cells. At the mouth or duct of the gland the columnar cells give place to a sciuamous epithelium resembling that of the anterior urethra. The structure of the epithelium of these glands gives evidence of considerable functional activity, which function is the production of a rather viscid nmcus. The purpose of this secretion is undoubtedly to lubricate and protect the anterior urethra. Because infections of these glands had been found only in adults between the ages of twenty and thirty-five years, it has been stated that they appear to reach their best development between these ages (1). In our clinic they have been found to occur in patients between the ages of twenty and forty-eight years inclusively. The fact that they do not apparently appear in ages under twenty remaiiiS to be explained. Possibly it may be due to a difference in the epithelial lining in very young patients. I have repeatedly examined the anterior urethras of young girls with chronic vaginitis, but have never succeeded in finding a suppurating focus in the urethra.

A great variety of organisms have been recovered from the human urethra (8): gonococcus, streptococcus, staphylococcus, diplococcus, colon bacillus, diptheria group of bacilli, pneumococcus, smegma bacilli, typhoid and typhus, pseudogonococci (an organism morphologically like the gonococcus, but Grampositive in reaction), and tuberculosis, and spirochaetae. The


INFECTIONS IN THE FEMALE URETHRA 5

Micrococcus catarrhalis (a Gram-negative diplococcus resembling the gonococcus) has also been found in the urethra (9) ; also in the vagina (10), from which locality it may easily gain entrance to the urethra. A Gram-negative diplococcus ha\'ing the form of the gonococcus, but with variations in size, has been demonstrated in preparations from fresh cultures (11). In smears taken from apparently normal urethrae, near the external meatus, we have always found some bacteria. Typhoid, typhus, and tuberculosis gain entry by invasion from within during the general infection of these diseases. A primary tuberculosis urethritis has yet to be definitely demonstrated. The inclusion bodies of Lindner (8), believed by many authorities to be the bacterium causing trachoma, have been recovered from the female urethra, the newborn of which patient had a conjunctivitis at the time. This same organism can be isolated from the infant's conjunctiva if smears are taken during the early onset of the inflammation. Virus from the mother's urethra, or from the infant's conjunctiva, or from a case of true trachoma will, when applied to the eyes of a monkey or human adult, produce trachoma. It is only when the germ gains entrance to the eye of the adult that true trachoma arises. So often has this been noted and by so many different observers that trachoma has been considered a venereal disease.

Infections in the urethra may be pathogenic or non-pathogenic, and also pj^ogenic or non-pj^ogenic. Because of its great prevalence and the extent of its ravages, the gonococcus is the infection of greatest importance. From the suppurating discharge expressed from the urethra Gram-negative intracellular diplococci can occasionally be demonstrated. But there are a gieat number of cases in which a great number of bacteria can be recovered without showing any presence of this bacterium, at least in smears made directly from the discharge. Knowing that the character of the gonococcus changes more or less during long habitation in the tissues, and also that a great variety of flora follow in its wake, chronic suppurating cases may be considered probably of Neisser origin unless otherwise demonstrated. Such a type of case may be shown in the following laboratory reports taken from the record of the Stanford Women's Clinic:


6 C. B. MOORE

No. 66510. July 22, 1918. Purulent-looking discharge expressed from urethral gland. Laboratory report of smear: jMany pus cells and a few Gram-negative intracellular diplococci.

August 29, 1918. Purulent-looking discharge expressed from urethral gland. Laboratory report of smear: Many pus cells and epithelial cells and a few Gram-negative intracellular diplococci.

January 29, 1919. Purulent-looking discharge expressed from urethral gland. Laboratory report of smear: Many pus cells and Gramnegative and Gram-positive bacilli; no Gram-negative intracellular diplococci.

March 3, 1919. Purulent-looking discharge expressed from urethral gland. Laboratory report of smear: Many Gram-negative bacilli; no Gram-negative intracellular diplococci.

In subsequent smears no Gram-negative intracellular diplococci were found, although a purulent-looking discharge could be expressed every time the patient was examined. Such a case clearly indicates a great difficulty encountered in any bacteriological search for this bacterium.

In some cases Gram-negative, intracellular diplococci may be present in the urethra without giving rise to any urethral signs or symptoms, as illustrated in the following record :

Xo. 74194. Cervicitis. Thick, mucopurulent discharge from the cervix. No discharge from the urethra; anterior urethra clear. Laboratory report : Cervical smear : Manj^ endothelial cells and a few Grampositive bacilli. No Gram-negative intracellular diplococci seeri. Smear from anterior urethra: Gram-negative intracellular diplococci. Many Gram-positive diplococci and bacilli.

What organism this is we cannot say at present. It appears that this bacterium is either in the incubation stage or else has remained here without producing any pathology.

B. coli infections producing suppurating para-urethral glands have been described by Fellner (12).

The changes in the urethra following pathogenic infections may be divided into two classes: those due to simple inflammation and those due to suppuration. In the former the lesion is like that of inflammation of a mucous membrane. These usually disappear in time or else yield to urinary antiseptics, except possibly some few chronic cases aff"ecting the intermediate region. The squamous epithelium of the anterior urethra does not offer


INFECTIONS IN THE FEMALE URETHRA 7

proper soil for the invasion of bacteria. Luys (6) has described the changes due to gonorihoeal infections. Tuberculosis (13) and syphihs (14, 15) have their specific lesions, which are described under these diseases.

The pyogenic infections are very important because of their frequency and chronicity. However, it should be noted that there can be expressed from some female urethras a material which is not one of suppuration. Sometimes a thick, creamy discharge, sometimes cheesy in consistency, can be expressed in which smegma bacilli have been found. At times one may be able to express a considerable amount of this material from the urethra. Occasionally a thin or thick white discharge is seen in the anterior urethra or can even be expressed directly from a gland, a material looking like that seen in the vagina at the time. This discharge has apparently passed from the latter plac0 and lodged in the anterior urethra or gained access to a gland. The stained smears from each locality are alike. This condition is demonstrated in the following record:

No. 78639. Moderately thick whitish discharge in vagina. Moderateh' thick whitish discharge expressed from gland in floor of anterior urethra, right side. Smears made from each locality. Laboratory report: Urethral smear: Examination shows many epithelial cells which are sc|uamous in type and have been denuded in masses. No pus cells nor lymphocj^tes seen. Many bacteria of various types, including large and small bacilli and small diplococci. Vaginal smear: Shows moderate number of squamous epithelial cells, a few lymphocytes, but no pus cells; numerous bacteria of various tj'pes, including large and small bacilli and small cocci occurring singly, in pairs, and in masses.

On two subsequent examinations at intervals of seven days, the same discharge was expressed from the same region of the urethra. Because the excretion resembles that seen in the vagina, macroscopically and microscopicallj', it is probable that the process was initiated by extension from the latter place or vice versa, and apparently does not extend beyond that of desquamation. In the chronic cases with suppurating infections we have a condition in which the original surface infection has disappeared; the bacteria have penetrated into the glands which offer the best soil for bacterial growth. In these minute


8 C. B. MOORE

epithelial pockets chronic inflammation with suppuration may go on indefinitely and without a local symptom. At every examination of these patients one or more drops of pus can be expressed into the urethral meatus from these suppurating glands.

When the duct of a suppurating gland becomes occluded there will be formed a para-urethral abscess which may vary from the size of a marble to that of a large walnut. In the larger abscesses the mucous membrane and vascular capillaries have been destroyed in places and the process has extended into the adjacent tissue. In this way blood sometimes becomes mixed with the pus.

An important point which may be considered here is the way in which the discharge from the urethra may be carried up into the parturient tract of an obstetrical patient. In his description of the function of Skene's glands, namely, lubrication during coitus, Kelly has described a mechanism of displacement and eversion of the urethra which may be seen to take place when a finger is introduced into the vagina. At the first contact the labia urethrae are separated. This opens the urethral orifice. The tendency of the act of penetration is to displace the distal end of the urethra dorsally. As the vaginal wall becomes impinged upon, the displacement will become even more marked and the urethral orifice directed into the vagina. Thus during the examination of an obstetrical patient the urethral meatus tends to become directed toward the examining finger. Pressure on the anterior vaginal wall expresses any infected contents of the urethral glands, which are then carried up into the vagina by the penetrating finger. For this reason, unless one be exceedingly careful, a digital examination of an obstetrical patient had better be done per rectum. Also by this same mechanism infections may be carried to or into the urethral meatus. This is probably the way in which B. coli enter the urinary tract in the newly married, giving rise to what is called by Sippel (16) 'Kohabitation Cystitis und Pyehtis.' No matter how sHght the abrasion of the urethral meatus which is directed into the vagina during the act of penetration, colon baciUi, which are commonly present in this region, become rubbed in and thereby enter the urethral lymphatics and ascend. Some of these cases of B. coli infection disappear spontaneously; others lose their acute character, if they had any, and continue without symptoms, a chronic condition with acute exacerbations of pyelocystitis' commonly called by the laity 'bilious attacks.' This is also a probable way in which pyelitis of pregnancy develops.

Whene\'er a suppurating discharge can be expressed from the urethral glands I do not think it worth while to treat the infection with antiseptic instillation into the urethra or even directly into the ducts of the gland. ]\Iany of the cases so treated continue to discharge pus with little or no mterruption. If the patient is kept under observation long enough, it will sometimes be found that what was thought to be cured was only pus-free for a time and has returned to its former suppurating condition.

Anterior urethral glands can easily be destroyed with the electric cautery and the suppurating condition terminated if the cauterization is sufficiently done. AATienever it is certain that the discharge expressed from the urethra is pus the anterior urethra should be cocainized with a 10 per cent solution of cocaine and the skenoscope (17) introduced. Sometimes one may be able to see the entrance to the ducts. With a finger in the vagina and pressure applied along the urethra, pus may be seen to appear at one or tw^o spots on the mucosa. In one instance, I saw as many as three drops appear at the same time in different places, and in a lateral position, not in the usual position on the floor of the urethra. At times one will be surprised to find that he is unable to express any discharge from a urethral gland, although some emerged from the meatus on examination before the instrument was introduced. This may be due to the fact that all of it had been expressed either from a gland or from the anterior urethra where it was lying. To tell whether or not it has come from a gland it is necessary to make the examination with the anterior urethra exposed so that the definite locality of any discharge may be seen. In case of failure to express anj^ excretion for the reason just mentioned, the patient may be requested to return for another exammation in a few days. The


10 C. B. MOORE

instrument is then introduced for the preliminary search. The gland will be found to have filled again, especially so if pus had been found, and the discharge will be seen to emerge from its orifice on pressure. With a small wire a search is made in each drop of pus for the entrance to the duct into w^hich the wire is passed as far as possible. This will act as a guide to direct the passage of a small wire electrocautery. Cauteiize until as much tissue is destroyed as one thinks advisable. Failing to find the entrance to the duct one may cauterize the region with no guide other than the eye. If on a subsequent visit the treatment has been found to be unsuccessful or pus has appeared from another locality, the treatment should be repeated. I have never seen any ill effects follow this treatment and no recurrence after the second cauterization, which is usually more thoroughly done than the first one. Healing is very prompt. Also, I have never seen any suppurating gland further than a few millimeters from the meatus; never beyond easy reach of the cautery, and never more than one or two in number, on one occasion three. This fact, together with Keibel's and Mall's embryonic studies, leads me to believe that all of these cases are those of skenitis.

Para-urethral abscesses which cannot be emptied through the duct should be treated surgically by incision and drainage.

I wish to thank Dr. Frank Ellsworth Blaisdell for his help and assistance in examining the histological sections and for his contributions of microphotographs which accompany this paper. Thanks is also due others of my confreres whose interest has been an encouragement.


INFECTIONS IN THE FEMALE URETHRA H

LITERATURE CITED

1 Kelly Howard A. 1933 Labia urethrae and Skene's glands. American

Medicine, vol. 6, pp. 429 and 465.

2 Skene, A. J. C. 1880 The anatomy and pathology of two important glands

of the female urethra. American Journal Obs., vol. 8, p. 265

3 KocHS, J. 1886 tJber die Gartnerschen Gauge beim Weibe. ' Arch, f . Gyna kologie. Red. von Crede; Bd. 20. Berlin.

4 ScHtJLLER, Max 1883 Ein Beitrag zur Anatomie der weiblichen Harnrohre.

o) Virchow's Archiv flir pathoiogische Anatomie und Physiologic und fiir klinische xMedicin, Bd. 94, S. 405. b) Festschrift f. Bernard Schultz, Berlin, Bd. 4, S. 16.

5 Keibel, Franz, and Mall, Franklin P. 1912 Human embryology, vol.

2, chap. 19, p. 965. J. B. Lippincott Company, Philadelphia and London.

6 LuYS, George A textbook of gonorrhoea, pp. 66-75. Bailliere, Tindall &

Cox, Covent Garden, London.

7 Van Cott, Joshua M. 1888 The histology and pathology of Skene's

glands. Brooklyn Med. Jour., vol. 1, p. 132.

8 Konigstein, H. Urethritis non-gonorrhoeal bei Mann und Frau. Hand buch der Geschlechtskrankheiten, Bd. 2, S. 518-575.

9 Avers, W. 1912 The Micrococcus catarrhalis as a cause of inflammation

in the genito-urinary tract. Amer. Jour. Surg. N. Y., March, p. 101.

10 GuRD, Eraser B. 1908 A contribution to the bacteriology of the female

genital tract with special reference to the gonococcus. Jour. Med. Research, vol. 18, N. S. 13, p. 291.

11 Steinschxeider 1893 tJber die Cultur der Gonokokken. Berliner klin ische Wochenschrift, July 24, S. 969.

12 Fellner, Otfried O. Einige Falle von paraurethraler Eiterung bei Weib.

Monatschr. f. Geburtsh. u. Gyn., Bd. 25, S. 319.

13 Hart.mann,H. 1935 Tuberculosehypertrophiqueet stenosantedel'urethre

chez la femme. Bull, et M. Sec. de chir. de Par., N. S., T. 32, pp. 956-958.

14 Douelle, M. 1901 Chancre syphilitique de I'urethre chez une femme.

T. D. mal. cutan. et syph.. Par., T. 13, pp. 467-471.

15 Lewembach, G. 1903 Die gummose Erkrankung der weiblichen L'rethrae.

Ztschr. f. Heilk., Wien u. Leipzig, 6 pi.; S. 51-91.

16 Sippel, A. 1912 Aufsteigende Infektion der Harnwege bei frisch verhei rateten Frauen. Kohabitation Cystitis und Pyelitis. Dut. med. Wochensch., Jun. 13, Bd. 28; S. 1138.

17 Moore, C. B. , 1918 Chronic gonorrhoeal skenitis. Treatment with the

electrocautery. Jour. Amer. Med. Assoc, Dec. 21, vol. 71, p. 2056.


PLATE 1


EXPLANATION" OF FIGURES


1 Cross-section of a female urethra near meatus of a newborn baby. G, glands; U, urethral canal. Abundant squamous epithelium.

2 Higher magnification of a region on figure 1. All sections of this specimen show this type of epithelium.

3 Cross-section of the whole specimen of a female urethra near meatus of a nine months' baby. As disclosed in embryonic studies, the glanudular budding is greater on the dorsal side.


12


INFECTIONS IN THE FEMALE URETHRA

C. B. MOORE


PLATE 1


' ' ' <f ■ -■■ ' \ "s. ^


^T^'^-^^'*^'-^


.V,

\



PLATE 2


AXATION f)F FIG


4 Cross-soot ion of a foinalc urethra iioar meatus of a nine months' baby ; made from a region of figure 3. G, gland; U, urethral canal.

5 Cross-section of a female urethra near meatus of a twenty-three-year-okl subject. Epithelium is squamous. This is undoulitedly a Skene's gland. V , urethral canal; D, duct; G, gland.

6 Higher magnification of a region on figure 5, but made lo,, mm. posterior to the section made of the latter. This section shows colunmar epithelium of the urethral canal, U , and the gland, G.

7 Cross-section of a female urethra near meatus of a forty-three-ycar-old subject. G, gland; E, epithelium; U, urethral canal.


INFECTIONS IN THE FEMALE URETHRA

C. B. MOORE


PLATE 2




-■


1^^^


k


/ /


i|t^^^^N«r



15


PLATE 3


KXPLANATION OF FIGURES


8 Dniwing of a .sagittal .section through the center of a female pelvis representing the urethral displacement on vaginal penetration.

9 Instrument in position for examinat ion and treatment. Exposure of drops of pus (A) in different localities of the urethra in different subjects.

10 Skenoscope.


16


INFECTIONS IN THE FEMALE URETHRA

C. B. MOORE


PLATE 3



Resumen por el autor, Richard E. Scammon, Universidad de Minnesota.

Un sencillo aparato de calcar para hacer reconstrucciones topograficas.

Este aparato ha sido ideado para hacer reconstrucciones graficas de fetos y otros objetos pequenos. Consiste esencialmente de dos partes: Una placa de vidrio cuadriculada, cuyas lineas distan entre si un centimetro, colocada sobre un tablero, y un ocular con un eje 6ptico establecido mediante un pequeiio orificio superior y una cruz formada por dos cerdas cruzadas, situada inferiormente.

En la base del ocular se ha cortado un cuadrante para permitir la orientacion de aquel con referenda a las lineas de la cuadricula. Los hordes del cuadrante son biselados y divididos en una escala milimetrica para medir pequenas distancias. Los ejemplares que se desea reconstruir se colocan sobre el tablero de la base, y despues de orientarlos con referenda a la linea basal de la cuadricula dividida en centimetros, se dibujan en papel cuadriculado por medio de una serie de lecturas sucesivas tomadas con el ocular.

Translation by Jos6 F. Nonidez Cornell Medical College, New York


AUTHOR S ABSTRACT OF THIS PAPER ISSUED BY THE BIBLIOGRAPHIC SERVICE, MARCH 28


A SIMPLE TRACING APPARATUS FOR MAKING TOPOGRAPHIC RECONSTRUCTIONS

RICHARD E. SCAMMON

Institute of Anatomy, University of Minnesota

THREE FIGURES

The study of certain phases of the anatomy of the fetus and infant is hindered somewhat by the lack of any simple method of making topographic reconstructions of the various organs and regions. Graphic reconstruction from microscopic sections, which is so successful in embryologic work, is generally impracticable here, for the preparation of even a few sets of serial sections of this material requires an almost prohibitive amount of time and labor, and the thorough decalcification necessary for the larger specimens usually causes serious shrinkage and distortion in the process of embedding. The usual methods employed in the study of adult topography are also inadequate for this work. Topographic reconstructions of the adult are generally made either by graphic reconstruction from free-hand transverse sections after the method first suggested by Henke or by plotting from fixed points which are estabhshed by setting long pins or skewers in the body in certain definite positions before dissection is begun. But to make accurate reconstructions of the smaller structures of the fetus and infant the sections must be cut so thin that they are extremely fragile and subject to distortion. And the fixed point method is very inconvenient both because of the difficulty in placing the pins firmly in position in the delicate tissues and because these pins make the subsequent dissection of the smaller regions almost impossible.

The apparatus which is described here was devised to overcome some of these difficulties, and after a considerable trial has been found sufficiently useful to warrant the publication of

19


THE ANATOMICAL RECORD, VOL.


20


RICHARD E. SCAMMON


an account of it. It consists essentially of a tracing stand, covered by a glass grating, and an eyepiece.

The stand is shown in figure 1. Its base is a slab of hardwood, 25 inches long, 17 inches wide, and 1.5 inches thick. Seven inches above this base is a sheet of heavy plate glass inclosed in a strong hardwood frame, which is supported at its corners by four brass rods. At one end these rods or legs are connected with the frame by hinges and firmly attached to the base-board


l-ATe GLASS ETCHED IM ICf



Fig. 1 Stand of reconstruction apparatus.

with screws. At the other their upper ends are screwed to the frame of the plate, but their lower ends are covered by rubber caps which rest freely on the base-board. This permits the frame to be raised so that large objects may be easily placed on the base-board below.

The glass plate is ruled with a centimeter grating and the lines of this grating are numbered or lettered consecutively at its margin. The middle longitudinal and the middle cross line of the grating are ruled a little heavier than the others and are filled with pigment to distinguish them as base lines (fig. 3).


A SIMPLE RECONSTRUCTION APPARATUS


21


\ Thejteyepiece is a brass tube 4 inches long and 0.8 inch in diameter (fig. 2, A). Its upper end is closed by a screw cap which contains a central pinhole opening (fig. 2, JB). At the bottom of the tube are cross-hairs of spun glass or very fine wire which are set a]^little|above its lower opening and cross in the optical




Fig. 2 Eyepiece of reconstruction apparatus. A, entire eyepiece; B, detail of screw cap with pinhole opening; C, detail of quadrant base.


axis of the tube directly in line with the pinhole opening in the cap. The lower end of the tube is set in the center of a circular plate of brass 2.4 inches in diameter and 0.2 inch thick. One quadrant of this base is cut away, its margins being so adjusted that they fall directly in line with the cross-hairs of the eyepiece.


22 RICHARD E. SCAMAION

The edges of the quadrant are beveled and are graduated in milhmeters, the zero points of the scales lying exactly 1 cm. from the optical center of the eyepiece (fig. 2, C).

The method of using the apparatus is simple. The specimen to be reconstructed is fixed firmly in a tray or better set in a base of plaster of Paris or hard wax. It is then placed on the base-board and adjusted so that its midhne corresponds approximately with the midline of the grating on the glass plate above it. Orientation points are then established by marking the specimen with dots of indelible ink or by setting small pins in it. At least three such points should be established as far apart as possible and in regions which will not be disturbed in the course of the subsequent dissection. A large sheet of coordinate paper is now numbered to correspond with the numbering of the grating, and base lines corresponding to those of the grating are drawn upon it. The exact position of the orientation points and the outlines and superficial landmarks of the specimen are now determined by successive readings with the eyepiece which is passed over the grating. As these determinations are made they are recorded in their proper places on the coordinate paper, and the first plot giving the outlines of the specimen is completed by connecting these points. After the outline is made the specimen may be dissected layer by layer and as the different structures are exposed they may be outlined in their proper positions on the plot by replacing the specimen under the grating, adjusting the orientation points to their recorded positions, and taking the necessary readings with the eyepiece. With a little practice this process can be carried out quite rapidly. Readings with the eyepiece to half-centimeters can be made directly from the lines of the grating and readings to half-millimeters by using the scales on the margins of the quadrant. The specimen should be strongly illuminated when the readmgs are made. Orthographic projection is assured by the use of the eyepiece with a vertical optical axis established by the pinhole opening and crosshairs. It is possible to make the reconstruction at any magnification desired by modifying the scale of the coordinate paper.


A SIMPLE RECONSTRUCTION APPARATUS 23

A



Fig. 3 Reconstruction of the abdominal and thoracic viscera of a full-term newborn infant. Made by H. J. Bower and W. C. Stillwell with the apparatus herein described. The reconstruction has been retraced and reduced to onehalf the original (natural) size. The centimeter scale of the grating is shown at the margins of the drawing. 'A-A and 0-0 are the longitudinal and cross baselines.


24 RICHARD E. SCAMMON

The chief sources of error in making reconstructions of this kind are due, first, to changes in the form of the specimen which may occur in the course of dissection and, second, to variations caused by the improper adjustment of the eyepiece. The first may be avoided, in a great measure, by partially embedding the specimen in a firm base of plaster or wax as mentioned above and by care in dissection. The second can be entirely eliminated if care is taken to see that the margins of the quadrant are either parallel or at right angles to the lines of the grating before each reading is made.

An example of a reconstruction by this method of the thoracic and abdominal viscera of a full-term stillborn infant is shown in figure 3. The original plotting has been retraced and inked, the pubhshed figure being one-half the size of the original.


-v^


Resumen por el autor, Richard E. Scammon, Universidad de Minnesota.

Nota sobre la relacion entre el peso de la tiroides y el del timo en el hombre.

La variaci6n de peso del timo y la tiroides en adultos jovenes, en apariencia normales (determinados por los datos de Dustin y Zunz) es muy grande. Los pesos de estos organos demuestran la existencia de una correlacion ligeramente negativa en la madurez temprana. Los pesos del timo y la tiroides del recien nacido varian tambien considerablemente, pero presentan una ligera correlaci6n positiva. Las conclusiones de Dustin y Zunz sobre el valor de estos datos como prueba de una correlacion funcional entre el timo y la tiroides no reciben confirmacion en los estudios del autor.

Translation by Jos6 F. Nonidoz Cornell Medical College. New York


ACTHOR S ABSTRACT OF THIS PAPER ISSUED BY THE BIBUOGR.VPHIC SERVICE, MARCH 28


A NOTE ON THE RELATION BETWEEN THE WEIGHT

OF THE THYROID AND THE WEIGHT OF

THE THYMUS IN MAN

RICHARD E. SCAMMON

Institute of Anatomy, University of Minnesota

In a recent publication Dust in and Zunz (1) have recorded some interesting observations on the weight of the thyroid and the thymus in early maturity. Their data are quite unique, consisting of weighings of the thj^oids and thymi of thirtyeight indi\dduals who, with one exception, died within fortyeight hours after receiving wounds in battle, and who came to autopsy within twelve hours or less after death. We are thus furnished with a series of records of the weight of the thymus in presumably normal young adults which greatly improves our knowledge of the later ponderal changes of this organ.

Dustin and Zunz have analyzed this material by means of tabulations and a graph in which the thymus weight is plotted against the thyroid weight. They found a negative correlation between thymus weight and thyroid weight in man, and they conclude that their results support the experimental findings of Gley (2) and others who have observed an increase in the thymus following thyroidectomy in amphibia.

Although this series of cases is very small for any statistical study, its unique character and the importance of the conclusions which have been drawn from its examination seem to warrant its further analysis by some of the simpler biometric methods. Accordingly, the standard de\dation and the coefficient of variation have been determined for the thymus and thyroid in the series and also the coefficient of correlation between the two organs. These determinations were fo^st made for the entire series of cases as given in the original article, and second for the same series with the omission of four cases which seem to be of doubtful value.

25


26 RICHARD E. SCAMMON

In the complete series the average weight of the thyroid is 32.0 ±2.4 grams, the standard deviation 21.8 grams, and the coefficient of variation 0.68. The average thymus weight is 15.6 ±0.7 grams, the standard deviation 7.07 grams and the coefficient of variation 0.45. The coefficient of correlation between the thyroid and the thymus is —0.265 with a probable error of ±0.102.

The second calculation was made from the series after the omission of the following cases.

Case 1, in which the weight of the thyroid was 134.54 grams, nearly four times the average weight of the group and over two times the weight of the next member of the series. It can scarcely be doubted that this great enlargement was associated with thyroid disease.

Cases 2 and 11, in which there was a complete involution of the thymus. As these cases were individuals aged twenty-five and twenty-eight years, respectively, it is most probable that the thymi had undergone accidental involution, presumably in some previous illness.

Case 38 was a youth but fourteen years old and cannot be properly included with a series of young adults, since the thymus undergoes profound weight changes in adolescence.

In the selected series, with these four cases omitted, the average thyroid weight was 26.6 ±1.41 grams, the standard deviation 12.26 grams, and the coefficient of variation 0.45. The average weight of the thymus was 16.2 ± 0.64 grams, the standard deviation 5.49 grams, and the coefficient of variation 0.33. The coefficient of correlation of the thyroid and thymus was —0.156 with a probable error of ±0.107.

These calculations show a negative correlation between the weight of the thyroid and the weight of the thymus in the complete series, as Dustin and Zunz suspected. But this correlation is so low and the probable error is so large that we are hardly justified in attaching any particular significance to it. This seems the more probable since when the four cases which are of very doubtful value are omitted the correlation drops to from — 0.265 to —0.156 and the probable error remains almost un


WEIGHT OF THE THYROID AND THYMUS IN aiAN 27

changed. A slight negative correlation might well exist between the two organs, since the thyroid follows the scheme of general body growth and increases a little in weight during the third decade, while the thymus decreases in absolute as well as relative weight after early adolescence. But this negative correlation does not warrant the assumption of a functional relation between the two organs; a similar correlation might be expected between the thymus and any of the viscera which follow the general scheme of the growth in mass of the body as a whole. ' In order to test this relation in another way I have calculated the coefficient of correlation of the thyroid and thymus in a series of twenty-five full-term newborn children. The data for this series were taken in part from the lists of cases reported by Valtorta (3) and Lomer (4) and in part from my own records. The average weight of the thyroid in this series was 3.4 ±0.24 grams, the standard deviation 1.8 grams, and the coefficient of variation 0.53. The average thymus weight was 14.2 ±0.90 grams, the standard deviation 6.7 grams, and the coefficient of variation 0.47. The coefficient of correlation of the thymus and thyroid was -1-0.19 with a probable error of ±0.08. Thus in the newborn, as in the adult, the variability of the th>^Tlus and the thyroid is very great and the correlation between the two organs is quite small. But, in contrast to the adult, the sHght correlation w^hich does exist in the newborn is a positive one.

These figures indicate that any correlation which may exist between the weights of the thyroid and the thymus is inconstant in postnatal life, and they offer fittle if any support to the concept of a direct functional relation between the two organs.

LITERATURE CITED

1 DusTiN, A. p., ET ZuNz, E. 1918 A propos des correlations fonctionnelles

entre le thymus et le corps thyroide. Journ. de Physiol, et do Pathol. Gen.,T. 17, pp. 905-911.

2 Gley, E. 1909 Glande thyroide et thymus. C. R. Soc. Biol. Paris, T. 66,

p. 1007.

3 Valtorta, F. 1909 Richerche sullo sviluppo dei visceri del feto. La indi vidualita nel neonato. Ann. Ostet. e Ginecol., T. 31, pp. 673-713.

4 Lomer 1889 Ueber Gewichtsbestimmung der einzelnen Organe Neugebo rener. Zeitschr. f. Geburtsh. u. Gynakol., Bd. 16, S. 106-130.


Resumen por el autor, George B. Wislocki, Johns Hopkins Medical School.

Observaciones sobre el comportamiento de la tinta china inyectada en animales durante la prefiez.

Experimentos llevados a cabo durante muchos afios han venido a demostrar que las partfculas inertes que flotan en la circulaci6n materna no pueden atravesar la placenta y penetrar en el feto. La explicacion de este fen6meno, mediante el cual el material en suspension no atraviesa la placenta o las membranas fetales, no ha sido hallada mas que para un grupo de substancias, esto es, los colorantes vitales. Estos colorantes, conforme Goldmann ha demostrado en el caso de la rata y raton, son absorbidos y acumulados en el epitelio cori6nico y las celulas de la membrana vitelina, y de este modo se previene su penetracion en el feto. El autor ha inyectado granulos de carbon suspendidos en acacia (tinta china) en una serie de conejillos de indias, conejos, gatos y perros prefiados. Los animales fueron sacrificados despues de unos cuantos dias y los tejidos examinados. El autor ha podido observar que los granulos de carb6n se depositan en el higado, bazo, pulmones y medula 6sea de la madre. En la placenta, membranas fetales y 6rganos de los fetos no pudo hallar carb6n, ni aiin estudiandolos bajo el microscopio. La conclusi6n que se deriva de la repulsi6n de las particulas de tinta por las celulas de la placenta y membranas fetales es que dichas celulas son incapaces de absorber o fagocitar material extrano de tamano grosero, flotante en la sangre. El limite del tamafio de las particulas que pueden absorber debe estar localizado entre el de una suspensi6n grosera, tal como la tinta china, y una dispersi6n ultramicrosc6pica, como el azul trypan.

Translation by Jos6 F. \onidrz Cornell Mediral College. \ew York


AUTHOR S ABSTRACT OF THIS PAPER ISSUED BT THE BIBLIOGRAPHIC SERVICE, MARCH 28


OBSERVATIONS UPON THE BEHAVIOR OF CARBON GRANULES INJECTED INTO PREGNANT ANIMALS

GEORGE B. WISLOCKI

Department of Anatomy, Johns Hopkins Medical School

It has long been known that certain cells of the body possess the power of removing foreign particulate matter from the bloodstream. Thus, when foreign particles, such as the carbon granules of india ink, are injected into the circulation of an animal, they are completely removed from the blood-stream in a remarkably short period of time. Gross and microscopic examination of the tissues of the animal reveals that the endothelial cells in certain organs have removed the ink from the circulation. The endothelial cells lining the sinusoidal channels of the liver and spleen are found heavily laden with the foreign particles. In addition to the granules of carbon which have been actually phagocytized, aggregations of the particulate matter into tiny clumps are found within the lumen of the blood sinuses. The bone-marrow in many animals is the site of a similar but subordinate process.

The question of the behavior of the cells of the placenta toward particulate matter circulating in the blood-stream has been only incompletely investigated. Recent writers on the problem of placental transmission, namely, Zuntz ('04), Kehrer ('08), and Hofbauer ('10), concur in the statement that particulate matter does not pass from the maternal into the fetal bloodstream. The explanation of the failure of suspended material to pass through the placenta or fetal membranes has not been 'given except for one group of substances, namely, the vital dyes. The vital dyes, which are ultramicroscopic dispersions of certain of the acid azo dyes have been rather fully investigated by Goldmann ('09). He showed that when these dyes are introduced into the blood-stream of a pregnant mouse or rat,

29


30 GEORGE B. WISLOCKI

they stain the maternal tissues, the placenta, and the outermost fetal membrane, but fail to stain the fetus. He discovered that the reason for this apparently was that the dye-stuffs were absorbed and stored by the cells of the chorion and \dtelline membrane and thereby prevented from entering the fetus.

It has, however, not been determined w^hether more coarsely dispersed substances than the Vital dyes,' such as the carbon granules of india ink, are similarly phagocytized and stored bj^ the cells of the placenta and fetal membranes or whether they are completely rejected by these cells. In the literature one finds numerous brief statements regarding the fate of coarse particulate substances injected into the blood-stream of pregnant animals. The earlier experimental work is surprisingly contradictory and but little unportance can be assigned to most of it, as the observations were made on an insufficient number of animals and the methods employed were often open to criticism. Thus, Reitz ('68) described cinnabar (red sulphide of mercury) in the tissues of a rabbit fetus after injecting the mother; Caspary ('77) reported a similar result with cinnabar in a rabbit; Perls ('77) recorded the passage of cinnabar and ultramarine into the fetuses in several rabbits and dogs; Mars ('80) observed the passage of a number of emulsified substances into rabbit fetuses, and, finally, Pyle ('84) stated that he observed the passage of ultramarine into a series of rabbit fetuses.

On the other hand, Hoffmann and Langhan ('69) failed to find cinnabar in the fetuses of a rabbit which they injected; Fehling ('77) and Ahlfeld ('77) reported the failure to find india ink in the liver, kidneys, or blood of the fetuses of several rabbits, and ]\Iiropolsky ('85) obtained similar negative results with cinnabar.

Krukenberg ('88), who can be said to have undertaken the first thorough investigation of this kind, injected a suspension of barium sulphate into one series of pregnant rabbits and a non-pathogenic organism, B. prodigiosus, into another series. Neither particles of barium sulphate nor organisms were recoverable from the tissues of the fetuses. His experiments left little doubt that particulate materials, such as he employed, are not transmitted from mother to fetus.


CARBON GRANULES INJECTED INTO PREGNANT ANIMALS 31

Hofbauer ('10) obtained similar results after injecting colloidal silver and silicium into several pregnant animals. Neither of the substances could be found in the fetal organs.

Finally, Goldmann ('09) undertook his experiments with acid azo dyes, and showed that they, too, were not transmitted to the fetus. Goldmann's report contains the only description of the microscopic examination of the placenta and fetal membranes. In the mouse and rat the giant-cells, the chorionic ectoderm of the labyrinth, and the epithelium of the vitelline membrane were found heavily laden with granules of dye; these cellular accumulations of the dye-stuff were looked upon as evidencing the protective mechanisms of the fetus.

In the present experiments a filtered solution of India ink was used. The ink was administered intravenously to a series of pregnant animals, consisting of one dog, three cats, three rabbits, and three guinea-pigs. The amount of ink injected was regulated according to the size of the animals, the guinea-pigs receiving 1 cc, the rabbits and cats 5 cc, the dog 15 cc, on two successive days. The animals were sacrificed one or two days after the last injection.

The gross distribution of the india ink was essentially the same in all the species of animals examined. At autopsy the liver and spleen were found to be deep black and the lungs presented a grayish appearance. The bone-marrow in the rabbit was of the same color as the liver and spleen; in the guinea-pig it was not so black, while in the cat and dog its color appeared to be normal. The uterus appeared unstained. The placentae, fetal membranes, and the fetuses showed nothing to the naked eye suggesting the presence of ink particles in these tissues. The remaining organs and tissues of the animals appeared normal. The findings in gross, therefore, indicated that the injected ink granules had in whole or greater part been segregated in the liver, spleen, bone-marrow, and lungs, and that none had been deposited in the placentae, fetal membranes, or fetuses.

Microscopic examination revealed the characteristic deposition of the carbon particles in the endothelial phagocytes of the liver, spleen, and bone-marrow. Particles, in part free and in part


32 GEORGE B. WISLOCKI

phagocytized, were also found, to a slight extent, in the interalveolar septa of the lungs. In the remaining organs and tissues of the body, with the exception of a few particles occasionally caught in a blood vessel or phagocytized within an endothelial cell, the carbon granules of the India ink were conspicuously absent.

No carbon particles could be found on examining the placentae. The chorionic epithelium, which in varying patterns is the predominating tissue in them all, showed no evidence of having absorbed particles of ink. The endothelial cells, which in the cat's and dog's placentae completely line the maternal vessels, had not the power of phagocytizing ink particles as had the endothelium of the liver, spleen, and bone-marrow. None of the ink-particles had agglutinated in either the maternal vessels of the dog's and cat's placentae, or in the corresponding sinuses of the rabbit's and guinea-pig's placentae, as they do in the sinuses of the liver and spleen. In the columnar cells of the chorion which flank the placentae of the dog and cat, known respectively as the 'green' and 'brown borders,' no carbon was visible. Nor were particles of ink discovered in the cells covering the vitelline membrane which in the rabbit and guinea-pig forms the outermost fetal membrane and faces the uterine mucosa.

The absence of particles of india ink in all these localities is surprising, since in vitally stained animals these same cells, namely, the chorionic epithelium and the epithelium of the vitelline membrane, are heavily laden with minute granules of trypan blue.

The conclusion to be drawn from the rejection of the ink particles by the cells of the placentae and fetal membranes is that they are incapable of absorbing or phagocytizing coarse, foreign particulate matter afloat in the blood-stream. The limit of the size of particles which they are capable of accepting must lie somewhere between that of a coarse suspension, such as india ink, and an ultramicroscopic dispersion, such as trypan blue. Trypan blue in turn, although absorbed by the chorionic epithelium and fetal membranes, is incapable of entering the


CARBON GRANULES INJECTED INTO PREGNANT ANIMALS 33

fetal circulation as true solutions have been shown readily to do. Trypan blue, however, may be on the border line of transniissibility, since traces of it actually enter the fetal circulation in the rabbit and guinea-pig.

LITERATURE CITED

Ahlfeld, F. 1887 Zur Frage ueber den Uebergang geformter Elcmente von

Mutter auf Kind. Centralbl. f. Gyn., Bd. 1, S. 265. Caspary, J. 1877 Zur Genese der hereditaren Syphilis. Vierteljahrresschr.

f. Dermat u. Syph., Bd. 4, S. 491. Fehling, H. 1877 Beitraege zur Physiologie des placentaren Stoffverkehrs.

Arch, f Gyn., Bd. 11, S. 523. GoLDMANN, E. E. 1909 Die aeussere und innere Sekretion des gesundcn und

kranken Organismus im Lichte der ' vitalen Faerbung. ' Teil 1 . Beitr.

z. klin. Chir., Bd. 64, S. 192. HoFBAUER, J. 1905 Grundziige einer Biologie der menschlichen Plazenta.

Wien und Leipzig. Hoffman, F. A., ujio P. Langbrhans 1867 Ueber den Verbleib des in die Circulation eingeflihrten Zinnobers. Virchow's Archiv f. path. Anat.,

Bd. 48, S. 304. Kehrer, E. 1907 Der plazentare Stoffaustausch in seiner physiologischen

und pathologischen Bedeutung. Wurz. Abhandl. a. d. Gesammtgeb.

d. prakt. Med., Bd. 7, S. 17. Krukenberg, G. Experimentelle Untersuchungen iiber den Ubergang geformter Elemente von der Mutter zur Frucht. Arch. f. Gyn., Bd. 31, S. 313. Mars, A. 1880 Ueber den Uebergang geformter Elemente aus dem Kreislauf

der Mutter in den des Foetus. Jahresbericht ueber d. gesammte Med.,

Virchow-Hirsch, Bd. 1, S. 81. MiROPOLSKY, M. 1887 Du passage dans le sang du foetus des substances solides

contennes dans le sang de la mere. Archives de Physiologie, T. 6, p.

101. Perls 1879 Lehrbuch d. allgem. Pathol., Bd. 2, S. 266. Pyle, J. P. 1884 An experimental research on the utero-placental circulation.

Phila. Med. Times, vol. 14, p. 711. Reitz, W. 1868 Ueber die passiven Wanderungen von Zinnoberkornchen durch

den thierischen Organismus. Berichte der Wiener Akad. Math.

naturw. Classe, Bd. 57, S. 8. ZuNTz, L. 1908 Der Stoffaustausch zwischen Mutter und Frucht. Ergebnisse

der Physiologie, Bd. 7, S. 403-443.


THE ANATOMICAL RECORD, VOL. 21, NO. 1


THIRTY-SEVENTH SESSION

Wistar Institute of Anatomy and Biology, Philadelphia March 24, 25 and 26, 1921

Thursday, March 24, 9.30 a.m.

The Thirty-seventh Session of the American Association of Anatomists was called to order by President Charles F. W. McClure, who appointed the following committees:

Committee on N ominations for 1921: Professor Ross G. Harrison, Chairman, and Professors Henry H. Donaldson and G. Carl Huber.

Auditing Committee: Professor F. T. Lewis, chairman, and Professor Stacy R. Guild.

The remaining morning session was devoted to the presenta ■ tion of scientific papers.

Friday, March 25, 11.30 a.m. Association Business Meeting, President Charles F. W. McClure, presiding.

The Secretary reported that the minutes of the Thirty-sixth Session were printed in full in The Anatomical Record, volume 18, number 3, pages 211 to 218. On motion, seconded and carried, the minutes of the Thirty-sixth Session were approved by the Association as printed in The Anatomical Record.

Professor F. T. Lewis reported for the Auditing Committee as follows: The undersigned Auditing Committee has examined the accounts of Doctor Charles R. Stockard, Secretary-Treasurer of the Association of Anatomists, and finds the same to be correct with proper vouchers for expenditures and bank balance on December 29, 1920, of 8164.40.

[Signed] F. T. Lew^s,

Stacy R. Guild

35


36 AMERICAN ASSOCIATION OF ANATOMISTS

The Treasurer made the following report for the year 1920:

Balance on hand January 20, 1920, when accounts were last

audited $173.12

Receipts from dues 1920 2,521.-43

Total deposits $2,694.55

Expenditures for 1920:

Expenses Secretary-Treasurer, Washington Meeting $36.08

Postage and Telegrams 44.90

Printing and Stationery 160.75

Collection and exchange on drafts 3.67

Stenography, typewriting 48.75

Wistar Institute, subscriptions to Journal of Anatomy,

Anatomical Record, etc 2,236.00

Total expenditures $2,530.15

Balance on hand $164.40

Balance on hand deposited in the name of the American Association of Anatomists in the Corn Exchange Bank, New York City.

On motion the report of the Auditing Committee and the Treasurer were accepted and adopted.

The Committee on Nominations, through its Chairman, Professor H, H. Donaldson, placed before the Association the following names for members of the Executive Committee, term expiring 1924, Professors S. W. Ranson and R. J. Terry.

On motion the Secretary was instructed to cast a ballot for the election of the above named.

The Secretary presented the following names recommended by the Executive Committee for election to membership in the American Association of Anatomists:

Abbott, Maude E., A.B., CM., M.D., Curator of the Medical Museum, McGill University, Montreal, Canada.

Allen, Edgar, Ph.B., A.M., Instructor in Anatomy, Washington University School of Medicine, ^555 McKinley Averiue, St. Louis, Mo.

Alford, Leland Barton, A.B., M.D., Associate in Clinical Neurology, Washington University School of Medicine, Humboldt Building, St. Louis, Mo.

Blair, Vilray Papin, A.M., M.D., Associate in Clinical Surgery, Washington University School of Medicine, Metropolitan Building, St. Louis, Mo.

Brooks, Barney, B.S., M.D., Associate in Clinical Surgery, Washington University School of Medicine, 4918 Forest Park Boulevard, St. Louis, Mo.


PROCEEDINGS 37

Dart, Raymond A., M.B., Ch.M., M.Sc, Demonstrator in Anatomy, University College, Gower St., London, W. C. 1, England. Temporary Address: Johns Hopkins Medical School, Baltimore, Md.

Davis, Warrex B., M.D., Instructor in Anatumv, Jefferson Medical College 135 S. 18th Street, Philadelphia, Pa.

De Carlo, John, M.B., Instructor in Topographic and Applied Anatomy, Jefferson Medical College, IIU Ellsicorth St., Philadelphia, Pa.

Dendy, Arthur, D.Sc, F.R.S., Professor of Zoology, University of Loyidon, King's College, Strand W. C, London, England.

Garcia, Arturo, A.B., M.D., Professor of Anatomy, College of Medicine and Surgery, Manila, Philippine Islands.

Graves, William W., M.D., Professor of Nervous and Mental Diseases, St. Louis University School of Medicine, Metropolitan Building, St. Louis, Mo.

Gregory, William King, A.M., Ph.D., Curator of Comparative Anatomy, American Museum of Natural History, 77th Street and Central Park West, New York City.

George, Wesley Critz, A.M., Ph.D., Associate Professor of Histology and Embryology, University of North Carolina Medical School, Chapel Hill, North Carolina.

Hartman, Carl G., Ph.D., Associate Professor of Zoology, University cf Texas, Austin, Texas.

Hausman, Louis, A.B., M.D., Instructor in Psychiatry, Johns Hopkins Hospital, Baltimore, Md.

Hill, Eben Clayton, A.B., M.D., Instructor in Anatomy, Johns Hopkins Medical School, Baltimore, Md.

HuGHSON, Walter, S.B., M.D., Assistant in Anatomy, Johns Hopkins Medical School, Baltimore, Md.

IxouYE, MicHio, J\I.D., Professor of Anatomy, Tokyo Imperial University, Tokyo, Japan. '

Levi, Giuseppe, M.D., Professor of Anatomy, University of Torino, Torino, Italy.

Meaker, Samuel R., A.B., M.D., Teaching Fellow, Department of Anatomy, Harvard Medical School, Boston, Mass.

Naxagas, Juan Cancia, M.D., Assistant Professor of Anatomy, College of Medicine and Surgery, Manila, Philippine Islands. (Temporary address — Dept. of Anatomy, Johns Hopkins Medical School, Baltimore.)

Nicholas, John Spangler, B.S., M.S., University Fellow in Zoology, Osborn Zoological Laboratory, Yale University, New Haven, Conn.

NoNiDEZ, Jose F., Sc.M., Sc.D., Instructor in Anatomy, Cornell University Medical College, 1st Avenue and 28th Street, New York City.

Patten, Bradley Merrill, A.M., Ph.D., Assistant Professor of Histology and Embryology, School of Medicine, Western Reserve University, 1353 East 9th Street, Cleveland, Ohio.

Perkins, Orman C, A.M., Assistant Professor of Anatomy, Long Island College Hospital, 335 Henry St., Brooklyn, New York.

Sachs, Ernest, A.B., M.D., Professor of Clinical and Neurological Surgery, Washington University School of Medicine, 97 Arundel Place, St. Louis, Mo.

Shellshear, Joseph Lexden, :M.B., Ch.M., Demonstrator of Anatomy, University College, Gower St., London, W. C. 1, England. (Presetit address— Dept. of Anatomy, Johns Hopkins Medical School, Baltimore.)


38 AMERICAN ASSOCIATION OF ANATOMISTS

Smith, David T., A.B., ^Medical Student, Johns Hopkins Medical School, Baltimore, Md.

Stone, Leon Stansfield, Ph.B., Assistant in Anatomy, Medical College, Yale University, New Haven, Conn.

Stone, Robert S., B.A., Assistant in Anatomy, Peking Union Medical College, Peking, China.

Stopford, John Sebastian B., I\I.D., Professor of Anatomy, University of Manchester, Manchester, England.

Swingle, W. W., Ph.D., Instructor in Zoology, Yale University, New Haven, Conn.

van der Horst, C. J., Ph.D., Zoologisch Laboratorium, PI. Muidergracht 34, Amsterdam, Holland.

Walmsley, Thomas, M.D., Professor of Anatomy, Queens University of Belfast, Belfast, Ireland.

WooLLARD, Herbert T., M.D., Demonstrator of Anatomy, University College, Gower St., London, W. C. 1, England.

On motion, the Secretary was instructed to cast a ballot for all the candidates proposed by the Executive Committee. Carried.

The Secretary then announced the following names as dropped from the list of members on account of non-payment of dues for the past two years:

Dr. a. E. Amsbaugh, Letterman Hospital, San Francisco. Dr. Robert S. Outsell, University of Minnesota. Dr. John A. Kittleson, University of Nebraska, Omaha. Dr. William E. McCormack, University of Louisville. Dr. George Walker, Johns Hopkins Medical School.

It was announced that the Executive Committee had voted to hold the next annual meeting at Yale University, New Haven, Conn., during the last week of December, 1921. The Federation of Biological Societies holds its meeting in New Haven at the same time.

A Committee on Editorship of Journals was elected by the Executive Committee following the last meeting: C. R. Stockard, Chairman; CM. Jackson, G. L. Streeter, R. J. Terry and C. R. Bardeen.

The Committee on Editorship of Journals reported as follows :


PROCEEDINGS 39

PROPOSED ORGANIZATION OF A JOURNAL COMMITTEE

OF THE AMERICAN ASSOCIATION OF ANATOMISTS

AND ITS DUTIES.

1. There shall be organized a Journal Committee composed of five members elected by the Association.

2. The Committee shall be estabHshed in 1921, as follows: Ten members of the Association shall be nominated by the Executive Committee of the Association. Additional nominations may be made from the floor. Members of the Advisory Board of The Wistar_ Institute shall not be eUgible for nomination in 1921. Election shall be by ballot. The five receiving the largest number of ballots shall constitute the Committee. In case of a tie, the choice of those thus tying shall be by lot. Of the five thus chosen, the one receiving the greatest number of votes shall serve for five years, the next for four years, the next for three years, the next for two years and the next for one year.

3. At the annual meeting in 1922, and subsequent years, one member shall be elected to serve for five years. Members are chgible for reelection. At least two nominations shall be made by the Executive Committee of the Association and other nominations may be made from the floor. The election shall be by ballot.

4. In case of resignation of a member of the committee, the place of the member thus resigning may be filled temporarily by appointment by the Committee itself until the next annual meeting of the society. At this meeting the place vacated shall be filled by nomination and ballot as outlined in Section 3, except that the election shall be for the balance of the unfulfilled term.

5. The duties of the Committee shall be:

(a) The selection of a responsible Editor for The American Journal of Anatomy and of a responsible Editor for The Anatomical Record.

(b) The appointment of Associate Editors, if such are desirable, shall be made by the committee in consultation with the responsible Editor concerned.

(c) In conjunction with the responsible editors of the two journals and with the Director of The Wistar Institute, the outhning of the broad, general pohcies in the conduct of the journals.

(d) The making of an annual report to the Association concerning journal policies.

The report of the Committee was formally adopted by the Association.

The Executive Committee in conformance with Section 2 of the report later nominated ten members of the Association as candidates for membership on the Journal Committee of five. One other name was added by nomination from the floor.


40 AMERICAN ASSOCIATION OF ANATOMISTS

^lembers of the Association then cast their ballots for five of these names with the following result :

C. E. Stockard was elected to serve for five j^ears;

G. L. Streeter to serve for four years;

CM. Jacksox to serve for three years; •

C. R. Bardeex to serve for two j'ears; and

F. T. Lewis to serve for one year.

The terms of service were arranged according to Sec. 2 of the report.

A proposed change in the constitution afTecting the length of term for the several officers of the Association was voted upon and defeated.

The president announced the nomination by the Executive Committee of Charles R. Stockard as the representative of the Association in the Division of Medical Sciences of the National Research Council.

On motion the nomination was accepted and the nominee elected to represent the Association.

The business session then adjourned.

Saturday, March 26. A Short Business Session followed THE morning Scientific Session.

The President announced that he had appointed Professor Ross G. Harrison as a delegate to represent the Association at The Second International Eugenics Congress which meets in New York City, September 22-28, 1921.

The Journal Committe reported the selection of Charles R. Stockard as Managing Editor of The American Journal of Anatomy, and John Lewis Bremer as ^Managing Editor of The Anatomical Record. ""

The place on the Journal Committee made vacant by the selection of Dr. Stockard as a Managing Editor was filled until the next annual meeting by the appointment of Dr. Ross G. Harrison.

President McClure was requested to present the greetings and best wishes of the Association to Professor George A. Piersol who was ill at his home in Philadelphia and unable to attend the meetings.


PROCEEDINGS 41

Professor S. W. Ranson introduced the following resolution:

Resolved: That the Association express its sincere thanks and appreciation to The Wistar Institute of Anatomy and Biology and to the local committee for the exceptional faciUties and accommodations which have served to make the meeting a marked success, and for the cordial hospitality that has been so generously extended to all in attendance.

Unanimously voted.

On motion the Session adjourned.

Charles R. Stockard,

Secretary of the Thirty-Seventh Session of the American Association of Anatomists


ABSTRACTS


/. On the development of the ameloblasts of the molars of the albino rat, with special reference to the enamel-free areas. William H. F. Addison and J. L. Appleton, Jr., University of Pennsylvania.

The crowns of the molar teeth in the albino rat, as in other rodents, have enamel-free areas on the cusps. These areas are always destitute of enamel from the time of first formation of the crown. The development of the enamel organ in these teeth is interesting, because of the differences which the functional and non-functional ameloblasts exhibit at different stages. The structure of the young enamel organ is similar to that of ordinary mammalian teeth. Up to the time of first formation of enamel and dentine (seen at first day after birth in first molar), all the cells of the ameloblastic layer are similar in size and structure. Soon after enamel formation has begun, however, differences appear in the formative and non-formative ameloblasts. Both classes of cells continue to grow for a time, but the non-formative cells grow more slowly and never attain the height of the formative cells. By the time the formative cells have attained their greatest height, the non-formative cells have begun to diminish in size. This diminution in size continues until the tooth erupts. At sixteen days the functional ameloblasts of the first molar measure 21^ and over in length and the non-formative cells about 7^. The developmental history of the enamel organ shows that this condition of enamel-free areas is secondary to the condition where enamel covers the entire crown. This again is evidence that persistently growing teeth (in which enamel is always to some degree lacking) have been derived from rooted teeth.

2. The oesirous cycle in the mouse. Edgar Allen (introduced by R. J. Terry),

Washington University School of Medicine.

Using Stockard and Papanicolaou's method of diagnosing oestrus by the cell contents of the vaginal fluid, I have studied the cycle in the mouse. The changes are similar to those in rats reported by Long-Evans ('20). The average duration of the cycle is from four to six daj's. External signs are a poor criterion of 'heat,' occurring in less than 60 per cent of cases, where oestrus was shown to be present by cell changes. During oestrus there is little uterine discharge, the changes in the vaginal contents being due primarilj' to an alternate infiltration into, and absence of leucocytes from, the vaginal epithelium, and a periodic formation and destruction of the granular and horny layers. There is no bleeding into the lumen of the uterine cornua, nor any extravasation of red blood corpuscles into the stroma, but only a slight destruction of the mucosa by leucocytosis. There is a hypersecretion of the uterine glands during oestrus resulting in distention of the cornua, effected by a constriction of the cervix; the vagina being usually dry. Goblet cells are abundant in the epithelium of the oviducts. In some mice ovulation is spontaneous at every oestrus, so that

43


44 AMERICAN ASSOCIATION OF ANATOMISTS

the ovaries are chiefly masses of corpora lutea. In others, where regular cycles have been recorded, no recent corpora lutea are present, while there are many atretic follicles which can be grouped to correspond to the recorded 'heat' periods. Consequently, all mice do not ovulate spontaneously during oestrus, and some ovulate only sporadically.

3. Ovogenesis in the sexually mature mouse. Edgar Allen (introduced by R. J. Terry), Washington University School of Medicine.

The question of the formation of definitive ova (those ovulated during sexual maturity) is still an open one. According to different investigators, they have been derived from, (1) the primordial ova; (2) from an embryonic proliferation of the germinal epithelium; (3) from a similar proliferation between birth and sexual maturity, and, (4) in a few instances by the continuance of ovogenesis from the germinal epithelium during the sex life of the individual. Kingery derives the definitive ova, in the mouse, from the germinal epithelium during a period from three to forty days after birth, stating that it does not continue after that time. At sexual maturity cyclic changes appear in the genital organs. The period preceding oestrous is the period of augmented growth. In ovaries of several mice killed at this time I have found a complete series of stages in ovogenesis from the germinal epithelum identical to those figures for earlier stages by Kingery. Therefore, ovogenesis is not complete at birth or before puberty, but continues on into sexually mature life, and the germinal epithelium of the ovary is homologous to that of the testis tubules.

4. On monozygotic human twins. Leslie B. Arey. Northwestern University Medical School.

Two specimens of early monozygotic human twins, each case unique of its kind, are presented. The first comprises twin embryos, each 12.3 mm. long, contained within a single amnion and chorion; except for some shrinkage of the entire specimen, the embryos are normal. Each possesses its own umbilical cord and yolk-stalk; the latter are inserted separately on a common yolk-sac. This furnishes for the first time direct proof of the origin of human identical twins from a single ovum. The second specimen is of normal monochorionic twin embryos, each lying within its own amnion. One member of the pair (11.5 mm. in length) has a normal yolk-stalk and sac (4.5 x6 mm.); the other individual (12 mm. long) lacks these structures completely, as gross and microscopic examination prove. Certain inferences are suggested: 1) Human monozygotic twins do not result from the separation of blastomeres or blastomere clusters at the earliest stages of cleavage, but from a later fission of the inner cell mass. 2) Nevertheless, the human ovum appears' to be rather rigid or determinate in its development; at least, in this case one embryo received all the yolk-sac formative cells. 3) The yolk-sac is not necessary for growth or differentiation; in fact, the twin individual lacking a yolk-sac is slightly the larger, while the correlation of menstrual age and body size coincides with the norm. 4) The yolksac and -stalk are not prerequisite to vasculogenesis; here was performed, as perfectly as ever may be expected, a natural experiment of ablation which demonstrates the independence of the embryo from such angioblastic ingrowths.


PROCEEDINGS


45


5. The 7nolor cortex of the brain of the sheep. Charles Bagley, Jr., Psychiatric Clinic, Johns Hopkins University.

A demonstration covering the histological study of the cortex of the brain of the sheep was given at the 1916 session of the American Association of Anatomists. The present communication is limited to the motor area of the brain of the sheep.

The motor cortex, as outlined in the early studies on the basis of histological structure alone, has been studied through means of electrical stimulation and some important differences brought out. The chief difference is the extension forward of the motor area to the most anterior pole of the brain and the elimination of an area of large pyramidal cells posterolateral to the principal motor area in the superior frontal convolution. Six areas can be satisfactorily outlined, the first three in the superior frontal convolution. Stimulation of the first two areas in the posterior extremity of the gyrus produces response in the limbs of the same and the opposite sides, while stimulation of the third area gives conjugate movement of the head and ej'es to the opposite side. Area 4 lies between the olfactory sulcus and the outer prolongation of the coronal sulcus, and when stimulated gives contraction of the face muscles, more marked in the lower lip of the opposite side. Area 5 is just to the outer side of the coronal sulcus in the mesial portion of the middle frontal convolution; stimulation of this area gives response in the face muscles of the same side. The cortex giving response to electrical stimulation has been extirpated in three parts and the material stained by the Marchi method. The first extirpation area was the entire superior frontal convolution and included areas 1,2, and 3. The second extirpation area included stimulation area 4, namely, that for the control of the opposite face muscles, while the third included area 5. Degeneration is clearly' demonstrated in the fibers of the pyramidal tract in all of the extirpation specimens; these fibers cannot be traced beyond the upper cervical cord.

6. The morphologic index. R. Bennett Bean, University of Virginia.

A new index has been devised wherebj^ any measurable character of a race, a group, a type, or an individual may be represented by a single numerical symbol. This sj^mbol is plus or minus, depending upon whether it is above or below the world average of the character. The morphologic index is actually the percentage above or below the average. This may be illustrated by contrasting a few morphologic indices of the Scotch and Negrito.



Morphologic


indices




CHARACTER


SCOTCH


APPROXIMA.TE WORLD AVERAGE


NEGRITO


Stature


+10.30

-18.75

-2.50

+0.96


cm.

165

80 SO 52


-6.07



+18.75


CpnlTilip indpv ....


+3.75


Skeletic index


-2.88




46 AMERICAN ASSOCIATION OF ANATOMISTS

The nasal index differentiates the Scotch and Negritos more than do the other three factors, and the stature is the next best differentiator.

The actual stature may be obtained from the morphologic index by multiplying the world average by the morphologic index and adding the result to or subtracting it from the world average. The actual stature of the Scotch is 175 cm. and of the Negritos is 148 cm. The nasal index, cephalic index, etc., may be obtained in like manner.

We may take the morphologic index of any group of Scotchmen or Negritos, or of any type within the group, or of any individual, and compare them ip many ways.

The morphologic index gives a numerical symbol that is simple, exact and convenient. It enables one to see at a glance the extent of variation from the world average, and thus to evaluate any factor, to determine its usefulness as a differentiator of race, group, type, or individual. It may also obviate the use of such terms as dolichocephalic, mesocephalic, brachycephalic; leptorrhine, mesorrhine, platyrrhine; leptoprosopic, mesoprosopic, euryprosopic; macroskele, mesatiskele, brachyskele.

7. The value of sections of the body in teaching sxirgical and medical anatomy. Ch.\rles W. Bonney, Jefferson Medical College.

The obect of this paper is not to describe the preparation of the sections of the body nor to discuss their value in teaching descriptive anatomy. The former is thoroughly understood by modern anatomists, the latter in use in numerous American Medical Colleges. It is desired to emphasize the value of sections in teaching applied, surgical and medical anatomy. For that purpose they have been employed at the Daniel Baugh Institute of Anatomy of the Jefferson Medical College for the last seven years. A brief description of the methods used together with illustrative examples will be presented. Lantern slides will be used.

8. The middle period in the development of the cloaca in chick embryos. Edward A. BoYDEN, Harvard Medical School.

This abstract deals with a portion of a comprehensive study embracing the development of the hindgut and associated regions in four species of bird embryos. Attention is called at this time to only a few points of interest: to the expansion of the allantois within the body cavity to form a pars coelomica of that organ; to the formation of a temporary urodaeal sinus w'hich resembles in a striking way the adult urodaeal chamber of certain snakes and lizards which functions in these animals as a dorsal bladder; and to some new facts concerning the origin and nature of the bursa of Fabricius.

Up to this time the primordium of the bursa has been usually described as a swelling in the posterior dorsal wall of the cloaca caused by the coalescence of vacuoles arising within the cloacal membrane during the fifth and sixth days of incubation (cf. Lillie, p. 317). This description gives the bursa a unique origin, setting it apart from all other derivatives of the gut tract and adding one more difficulty to the interpretation of an organ which has been a bone of contention among anatomists since its discovery in 1604 by Fabricius, who ascribed to it the function of a receptaculum seminis. As a result of a quantitative study of


PROCEEDINGS 47

chick embryos between the fourth and fifth days of incubation, designed originally to explain the nature of accessory diverticula found between the rectum and anal plate, it has been possible to demonstrate that the primordium of the bursa appears a day earlier than hithert supposed and in the form of a caudally directed diverticulum whose cavity at first is in direct continuity with the cavity of the cloaca. In its later development the bursa unites with the protodaeum in a manner that closely resembles the union of the proctodaeum with the anal sacs in turtle embryos. And there are other resemblances between these two organs which superficially suggest an homology. Whether this proves to be true or not it is probable that the bursa should be classed with those derivatives of the gut tract, likewise arising as diverticula, whose functions are now obscure, but whose histogenesis suggests lymphoid degeneration.

9. The earhj morphogenesis of the cerebral hemispheres of Amblystoma. H. S.

BtTRR, Yale University, School of Medicine.

A study of the early morphology of the cerebral hemispheres was suggested by some interesting results obtained in an experimental study of regeneration in the forebrain of Amblystoma. Evagination of the lateral wall of the neural tube occurs in the region of the confluence of the S. limitans and the S. diencephalicus ventralis and involves that portion of the lateral wall which intervenes between it and the lamina terminalis anteriorly. In this region lies the anlage of the olfactory bulb and the adjacent secondary olfactory centers, the latter crossed by the S. diencephalicus medius. The point of most rapid growth lies at the anterior end of the S. ventralis and seems to involve a short portion of the neural tube which lies between it and the lamina terminalis. Relatively little of the wall of the forebrain is evaginated, the definitive hemisphere growing very largely through the rapid increase in the number of cells forming the outpouching. This growth occurs principally at the anterior pole, producing rapid anterior elongation of the hemisphere. Growth in the dorsal and posterior region is much slower though greater than in the ventral region where growth is largely produced through the thickening of the walls. The successive development of fiber-tract systems shows that many nuclei develop in the hemispheres as a result of the ingrowths of the fiber tracts into the region involved. The nucleus medianus septi part'^nlarly shows evidence of growth after the appearance of the portion of the median forebrain tract which runs to it. From previous experimental work it can be stated that the primordia of the gray nuclei will develop to some extent without the ingrowth of tract systems, but the complete size development occurs only after nervous connections are established.

. 10. The growth of the external dimensions of the hitman body in the fetal period and its expression by empirical forrmdae. (Lantern.) L. A. Calkins (introduced by R. E. Scammon), Department of Obstetrics and Gynaecology, Tniversity of Minnesota.

A graphic and mathematical analysis of measurements of seventy external dimensions of the body of upward of 400 preserved fetuses 2.3 to 54 cm. in length. The uncorrected curves of these dimensions (plotted against body length) are of three types: a) straight lines; b) curves approaching straight lines, but deflected upward toward their terminations; c) curves approaching straight lines but


48 AMERICAN ASSOCIATION OF ANATOMISTS

deflected downward toward their terminations. Many larger specimens were injected. An extensive study of this technique shows that this causes the upward trend in most b curves, and that when eliminated they become straight lines. All downward deflected curves are of head dimensions affected by birth-molding. Observations on comparatively unmolded heads (breech extractions and caesarian sections, prove that these also are really straight. Only five curves (medianline measurements of upper parts of the body probably affected by head flexion) are not straight after elimination of artifacts.

External bodily dimensions plotted against body length (being, in general, straight lines) are expressed by the empirical formula, Y = aX ± b (Y, dimension; X, body length; a and b, constants). The constant b is positive for the head, zero for the thorax, and negative for the abdomen, pelvis and extremities.

It may be concluded: 1) The relative growth rates of the external body dimensions are established in the third month and remain unchanged until birth. 2) The growth of the external body dimensions in the fetal period follows the law of developmental direction.

n. Studies an the dynamics of histogenesis. IV. The biomechanical interaction of differential growth as a factor in the origin of bone. Eben J. Carey, Marquette School of Medicine.

Increased density or condensation is the chief physical property which characterizes osseous tissue. Is this quality self -engendered in the tissue' involved or is it the mechanical resultant of the interaction of differential growth? In a former communication by the writer evidence was presented in support of the idea that embryonic bone is the immediate consequence of induced stresses and not the product of an anticipated function. Many workers on bone development consider that stresses are induced in, and strains manifested by the skeleton only after birth when the body weight is sustained. If such is the case, why does bone form in the upper extremity of man at all? Experiments which have been devised to disprove the mechanical origin of bone have not carried their point. The fact that the blastemocartilaginous skeleton is an area of accelerated longitudinal growth and that the surrounding soft parts are retarded in longitudinal growth has been entirely overlooked.

Two areas in syncytial continuity and manifesting differential growth, as the skeletal and soft areas in the limb, exert an interaction. The zone of accelerated growth drags along the one of retarded growth, the latter in turn tends to slow down the speed or deflect the course of the former. This active interplay between growing parts tends to a dynamic equilibrium, but as long as one growing part is dominant and the other subdominant, growth and the resultant interaction and differentiation continue. The effect of interaction in the experimental production of double monsters is excellently treated in a recent monograph by Stockard (Am. Jour. Anat., 1921, vol. 28, pp. 115-277).

The stresses induced in the origin of bone are the result of growth and resistances. The accelerated growing blastemochondrogenous skeleton meets the foUowmg resistances: 1) Opposed growth of contiguous skeletal segments; 2) weight of related soft parts; 3) reactive elasticity of traction of the soft parts retarded in growth; 4) active muscular pull. It is imperative, therefore, that, 1) Growth and 2) Resistances to growtli be understood by the cmbryologist before


PROCEEDINGS 49

he can appreciate the importance of each factor. Both are active and formative during development, both are absolutely necessary to the realization of form and neither processes can be looked upon as more important in development than the other.

12. V. The law of density of a growing tissue: On the progressive augmentation of femoral density as the resistances to the grouih of the femiir increase. Ebex J. Carey, Marquette School of Medicine.

With the rapid increase of limb weight, and with increase of opposition to growth at the ends of the femur, together with the resistances manifested by muscular reaction, the density of the femur increases progressively. This increase in density is concomitant with the relative decrease in femoral volume as the growth of the limb advances. In an 18-mm. embryo the volume of the femur constitutes one-third of the entire limb, whereas its density is 0.33. In a 20-mm. embryo femoral volume is one-fourth that of the limb and its density is 0.37, whereas in the 50-mm. embryo the volume of the femur is one-seventh and the density is 0.43. The density of the femur in a 200-mm. embryo is 1.6 and the volume is one-sixteenth that of the limb.

THE LAW OF DENSITY OF A GROWING TISSUE; The density of a growing tissue 2S directly proportional to the resistances (pressure) encountered during growth.

13. VI. The law of relative volume of a growing tiss^ie: On the relative decrease of femoral volume as the resistances to the groivth of the femur increase. Eben J. Carey, Marquette School of Medicine.

The various steps in the increase of skeletal density, from the blastemal to the cartilage period, and, secondly, from the cartilage to the osseous period, in skeletal condensation, are considered simultaneously with those changes, extrinsic to the zone of femoral formation. During the early stages of development, the weight of the entire hind limb is supported by the femur's acting like a cantilever beam. The weight of the limb increases rapidly.. In an 18-mm. pig embryo the femur constitutes one-third of the volume of the limb and supports a weight of 0.013 grams. In a 20-Dam. embryo the femur constitutes one-fourth the volume of the limb and supports a weight of 0.018 gram, whereas at the oO-mm. stage of the developing embryo, the femur constitutes one-seventh of the volume of the limb and supports a weight of 0.25 gram. Later at the 20-cm. stage the femur constitutes only one-sixteenth of the volume of the limb, but it supports the greatly increased weight of 30 grams. In addition to sustaining the above weight, the femur is opposed in growth by the accelerated growth centers located proximally and distally. Finally, as development continues, the resistance presented to longitudinal femoral growth by the contracting musculature and elastically reacting soft parts are opposing factors to be considered as extrinsic pressure limiting the relative volume of the femur to the thigh, as growth continues.

THE LAW OF RELATIVE VOLUME OF A GROWING TISSUE: The relative volume of a groiving tisstie is inversely as the resistances (pressure) ichich it bears.


50 AMERICAN ASSOCIATION OF ANATOMISTS

14. VII. On the torsion of the developing femur. Eben J. Carey, Marquette School of Medicine.

That the femur undergoes a torsion during development has not been previously observed. This twist is objectively evident by observing the ventral aspect of a closely graded series of developing femora from the time the femur is approximately 3 mm. in length until it is 30 mm. in length. In a 3-mm. femur the head is in a direct line with a plane projected through the mid-ventrodorsal aspect of the shaft cutting through the center of the articular surface for the patella. This is objectively evident in a 3-mm. femur. With the next marked advance in development in a 9-mm. femur we find the head displaced mesiad. This torsion of the femur through an arc of 90° is in reality due to the torsion and development of the greater trochanter influenced by the traction of the attached gluteal muscles. This twist of the femur corresponds in time with the beginning and ending of limb rotation and with the period of greatest growth, differentiation, and activity of the thigh musculature.

15. VIII. The law of joint formation: Bio-mechanical interaction of differential gruvth as a factor in the origin of joints. Eben J. Carey, Marquette School of Medicine.

The blastemal skeleton of the acetabulum and the femur is apparently continuous. The femur, tibia, and fibula, and the foot plate progressively appear in the order named by the direct extension of the accelerated proliferation of the blastemal skeleton, comparable to the progressive caudal formation of metameres in th^ chick embryo. The first radical change from the apparently continuous to the segmental skeleton is seen in an embryo, 16 mm. long, by the appearance of a faintly curved line of compressed nuclei in the region of the future hipjoint. In an embryo 18 mm. in length another compression line is detected in the region of the future knee-joint.

1. By the continued opposition to growth between the contiguous centers of the segmental blastemal skeleton, mechanical compression occurs revealing the location of the future joint cavities.

2. The contour of the opposed surfaces constituting a joint is dependent on the intensity of the force of growth, per square millimeter of cross-section, of growing segments opposed in action, together with the force of muscular pull. That segment will possess the ball of a ball-and-socket joint which possesses the greater force of interstitial growth, longtitudinally per square millimeter of crosssection.

3. Joints, therefore, are not the cause of skeletal segmentation, they themselves are the mechanical resultants of compression of prior centers of accelerated growth, opposing each other in action in the segmental blastemochondrogenous skeleton.

4. THE LAW OF JOINT FORMATION: The contour of the opposed surfaces forming a joint is dependent xipon the intensity of the force of interstitial growth, per square millimeter of cross-section, of the segments forming a joint and upon the resistances to the growth of each skeletal segment.


PROCEEDINGS 51

16. IX. The law of direction of myogenesis: The bio-mechanical interaction of differential growth as a factor in the origin of muscular tissue. Ebex J. Carey, Marquette School of Medicine.

Is the physical property which characterizes the initiation of muscular differentiation, namely, specific elongation of the nuclei and spongioplasm, caused by a factor intrinsic or extrinsic to the zone of myogenesis? The writer has presented evidence of direct observation which proves that the latter and not the former is the case. In other words, muscle is the resultant of the tension, pulling out or traction to which a syncytial mass of mesenchyme is intermittently but progressively subjected by a related region of cells accelerated in growth.

It was shown formerly that the dominant zone of accelerated growth in the intestine is the epithelial tube. By expansion of the epithelial tube in spiral growth the surrounding mesenchyme was drawn out in tension resulting in helieoidal muscular differentiation. In the limb the zone of accelerated growth is the central segmental skeletal core. This draws out by traction the surrounding mesenchyme resulting in skeletal muscular differentiation. The zone of accelerated growth in the cardiac area is the progressive increase in the whirling volume of the bleod. This draws out the surrounding mesenchyme in tension corresponding to the direction of the vortex of blood resulting in spiral muscular differentiation. The detail proofs for these assertions will soon be published.

THE LAW OF DIRECTION OF MYOGENESIS: The elongation of a developing muscle is in the direction of the accelerated growth of an extrinsic dominant zone ichich draws out in tension the mesenchyme forming the muscle.

17. The development of the aster in the artificial parthenogenesis of the sand-dollar egg. Robert Chambers, Cornell University Medical College.

No noticeable changes occur in the cytoplasm or the nucleus of the eggs until long (half an hour or more) after both the butyric-acid and the hypertonic-solution treatments. The visible phenomenon peculiar to the parthenogenetically induced egg consists in the manner in which a fluid substance begins to separate out of the egg cytoplasm, preparatory to the formation of the preliminary single aster. In the sperm-fertilized egg radiations appear immediately about the sperm head, and the accumulation of the fluid substance is from the very start through the agency of the ray-like channels of the growing aster.

An optimum parthenogenetic treatment causes vacuoles to appear which fuse to form a central clear area about which radiations develop until an aster is formed corresponding exactly with the fully developed sperm aster of a normally inseminated egg. From now on the procedure is similar to that occurring in a sperm fertilized egg.

Over-treatment causes the appearance of many vacuoles scattered throughout the egg resulting in multiple asters. Under-treatment may result in the formation of a single aster which, however, periodically disappears and reappears as a single aster. A successful treatment not only causes a separating out of a liquid from the egg cytoplasm, but also induces a polarity within the resulting clear area to enable it to form two centers about which an amphiaster_may develop.


52 AMERICAN ASSOCIATION OF ANATOMISTS

18. The reaction of living cells in the tad-pole's tail toward injected starch granules. Eliot R. Clark and Eleanor Linton Clark, University of Missouri. Small quantities of starch (corn-starch and arrow root) were injected into the

transparent tails of frog larvae and the region of injection studied in the living during the subsequent hours and days.

Uncooked starch, boiled starch, and starch cooked just to the point of gelatinization were tried. The larvae were fixed in iodine at different periods of time after the injection.

Toward the uncooked starch granules the response was similar to that displayed toward foreign bodies, such as carbon and carmine. Leucocytes approached the starch grains and engulfed them and the starch remained inside the leucocytes indefinitely (over a month).

The boiled starch grains disintegrated within the first half hour after injection and after an hour no stain was obtained after treatment with iodine. Wandering cells moved toward the injection site.

In the case of the semi-cooked starch, near-by wandering cells moved very rapidly toward the injected material and within twenty minutes leucocytes began to emigrate from neighboring blood-vessels in very. large numbers. Within an hour the starch grains were all inside of leucocytes. The diapedesis of leucocytes continued for six hours or more. Leucocytes staining blue with iodine were demonstrated from three to four hours after the injection. The further stages in digestion were not followed since the characteristic reaction of dextrin or of glycogen was not obtained and our microchemical tests for sugar, injected into the tail fins, were unsuccessful.

Starch cooked to the point of gelatinization proved to be a most powerful chemotactic agent for leucocytes. The other tissue cells showed no response toward injected starch.

19. Cyclic changes in the ovaries and xderus of the soiv, and their relation to the mechanism of implantation of the embryos. George W. Corner, Johns Hopkins Medical School.

The author has completed a detailed study of the follicles, corpora lutea, and uteri of a large series of pregnant and nonpregnant animals killed at known stages throughout the oestrous cycle. The cycle averages twenty-one days in length. Ovulation is found to occur during oestrus; the corpora lutea complete their formation about the seventh day, and remain in full development from the seventh to the fifteenth day, thus surviving just long enough to cover the period of attachment of the embryos. If no embryos are present the corpora lutea degenerate about the fifteenth day.

A few daj^s before and during oestrus the uterine epithelium is in a state similar to that described by Stockard and Papanicolaou and by Long and Evans in the small rodents; but during the growth period of the corpus luteum the uterus undergoes histological changes culminating, from the eighth to the tenth day, in a state of enhanced epithelial activity. At this time the embryos, when present, are still unattached and are being shifted into position for implantation. From the tenth to the fifteenth day (the period of implantation), further elaborate changes take place by which the epithelium is brought to a state characteristic of early pregnancy in the implantation stage. If no embryos are present the same changes occur, but subside after the fifteenth day.


PROCEEDINGS 53

These results indicate that there is a correlation between the state of the corpus luteum and that of the uterus by which the uterus is prepared, after each ovulation, to receive embryos. A detailed and illustrated monograph will appear in the publication of the Carnegie Institution.

20. Digestion of different proteins by the mesenchyme and its derivatives in the tadpole. (Lantern.) Vera Danchakoff, Columbia University.

Though well known to exist within the multicellular organism the phagocytic digestive activity of the mesenchyme has not been much studied. Little is as yet known regarding the amount of digestive work accomplished in the organism by the mesenchyme, if given opportunity. Neither is the extent known to which this activity becomes a factor in the resistance which a multicellular organism offers to the growth of heterogeneous tissues even of such a great proliferative capacity, as, for example, the tumors.

The adult splenic mesenchyme of the fowl, as shown by me last year, is capable of ingesting and digesting, one by one, cells of a mammalian proliferating tumor. The mesenchyme and its derivatives, in the form of small wandering cells, in various tadpoles, will be shown to possess the power of digesting various proteins. The mesenchj'mal tissue within the tail of different tadpoles can be fed on finely particulated fibrin, edestin, coagulated albumen, and lecithin, the particles being of the size of a small fraction to a few diameters of a mesenchymal cell. The response to the sudden appearance of a large quantity of injected material is rapid from the part of the mesenchymal and wandering cells. Four to six hours after injection a great number of mesenchymal cells and of cells of the small lymphocyte type are found around and within the injected mass; about twenty-four hours after the injection all but the largest particles are ingested, and after three to four days no trace of the injected material is found.

The results of these experiments illustrate the great digestive capacity inherent in the mesenchymal and small lymphocyte cells of the amphibia during the tadpole stage. These cells can most effectively take care of comparatively huge masses of injected particulated protein, and like physiologically balanced unicellular organisms, if given opportunity, successfully perform their own digestive activity.

21. Further morphological evidence for the digestive capacity of adult splenic mesenchymein the fowl. Vera Daxchakoff and S.M. Seidlin, Columbia University. A new morphological evidence for the digestive capacity of the mesenchj-me

was brought forward by Danchakoff last year. The splenic reticular cells of the adult fowl were shown to be capable of surrounding and digesting the living cells of an actively proliferating mammalian tumor (the Ehrlich sarcoma). The encircling of the tumor cells by the mesenchyme, followed by digestion, as observed in Danchakoff's experiments, is the result of the immediate encounter of two living tissues. A further study of the digestive capacity of the mesenchyme was required in order to ascertain whether the living tumor cells were treated by the mesenchymal cells in the same manner as dead particles of mammalian protein would. Small particles of catgut were intimately mi.xed with mash of adult splenic tissue and grafts of this tissue made on the allantois of seven days chick embrj^os.


54 AMERICAN ASSOCIATION OF ANATOMISTS

The study of the grafts after five days' growth has shown the particles of catgut partlj' digested, partly attacked by the mesenchyme. Mesenchymal cells isolated and in the form of more or less huge plasmodia surround the catgut particles, the latter showing distinct indentations, which in outline often correspond to mesenchj^mal cells. The mesenchymal plasmodia close to the partly digested catgut contain vacuoles. The process of digestion where the catgut particles are small is very similar to that exercised by the mesenchyme against the cells of the Ehrlich sarcoma. The splenic mesenchymal cells of the adult fowl seem to be capable of exercising phagocytic and digestive activity regardless of whether this activity is directed against sterilized particles of heterogeneous dead tissue or against living heterogeneous tumor cells of certain physicochemical constitution.

22. A new interpretation of the morphology of the nervous system. Raymoxd A.

Dart and Joseph L. Shellshear (introduced by R. J. Terry), University of

London.

His ('68) promulgated his principle of ectodermal origin of neural tissue. Balfour and others extended this hypothesis to postulate a neural tube origin of all neuroblasts. Beard, Piatt, Landacre, and others have shown that a large proportion of the cranial ganglionic elements arises in the ectoderm lateral to the medullary area from certain areas called 'placodes.' Observations by J. P. Hill, Elliot Smith, and the authors have demonstrated a similar peripheral but entodcrmal origin in placodes for the visceral elements in the VII, IX, and X cranial nerves throughout Vertebrata. A radical revision of current conceptions is therefore necessitated.

The ' placodal' principle of a peripheral origin for all neuroblasts of the peripheral nervous system is of general application. The only point of agreement between students of the ontogeny and phylogeny of the sympathetic system is of the first appearance of the so-called 'primary anlagen' peripherally and in inextricable relationship with the mesodermal structures supplied thereby. That the sympathetic system develops independently of the neural tube was shown by Weber in 1851. A mesodermal origin of these neuroblasts must therefore be postulated and is demonstrable.

But these are not the only mesodermal neuroblasts. Concurrently with the differentiation of the somite from indifferent cells into the various 'supporting tissues' of the body there arise from similar 'indifferent cells' of the primitive somite the neuroblasts for the innervation of these tissues. The somite, then, has this jiroperty in common with definitive placodes previously described by various authors; it gives rise to a) neuroblasts and 6) supporting tissue. A rational phylogenetic and ontogenetic explanation is provided in this way for the proprioceptive senses. The anterior horn cells of the neural tube must, however, be appreciated as primarily 'extraneural.' The neural tube itself is considered as a series of bilaterally segmented placodes. The data entail further a revision of the conception of neurobiotaxis as put forward by Ariens Kappers. This principle is given wider application for the interpretation of the movements of sensory neuroblasts which move away from the 'source of stimulus.' The nervous systems of Vertebrata and Invertebrata are harmonized by the 'placodal' conception, nnd on hypothesis is promulgated to account for the origin of the


PROCEEDINGS 55

former. Finally, the problems of segmentation and the mesoderm are deemed to be more correctly appreciated from the new point of view.

23. Degeneration phenomena in the pelvic gland of the male Necturus. A. B.

Dawson, Loyola University School of Medicine.

Pelvic glands of males, killed during the late autumn and winter, exhibit degeneration phenomena similar in many respects to those recently described by Saguchi ('20) in the frog's pancreas under the title, 'physiological degeneration. ' Although numerous cells are degenerating, the gland is secreting actively. Nucleoli are not demonstrable in the normal cells and it seems impossible to interpret the large eosinophilic central corpuscle of the 'chromocyte' as being a result of nucleolar hyperchromasy. The nucleus undergoes successive changes characteristic of Flemming's chromatolysis. Some degenerating cells escape directly into the lumen of the tubule; others, however, are sooner or later taken up by neighboring normal secreting cells. Within the normal cells the plasma of the degenerating cells is digested and absorbed rapidly. The degenerating nuclei usually become separated into several portions, either by direct fragmentation or a process of gemmation, and are ultimately eliminated, along with the secretion of the normal cell, into the lumen of the tubule. No phagocytosis was observed in connection with this degeneration and no mitosis was evident at this period of the year. These intracellular corpuscles, derived from degenerating gland cells, resemble 'nebenkerne' and have been so interpreted by many investigators working on glands. The small spherical nuclear fragments simulate basophilic secretion granules.

Pelvic glands from animals killed in July present a very different picture. The lumina of the tubules are reduced to a minimum and mitotic figures are encountered very frequently. Large phagocytes filled with disintegrated cells are numerous.

2^. The growth of the brain and the spinal cord in the human fetus and its expression by empirical formulae. Halbert L. Dunn (introduced by R. E. Scammon), University of Minnesota.

A quantitative study of the growth of the brain and its parts and of the spinal cord in a series of 156 human fetuses ranging from 4 to 56 cm. in crown-heel length. The growth of the central nervous system in the fetal period follows, in a general way, the growth of the body, and its increase in weight and volume may be expressed by formulae similar in type to that expressing growth in body weight. Further analysis shows that three distinct subdivisions or varieties of this general type of growth may be recognized in the central nervous system. These are, 1) cerebral growth, which shows a slow but steady increase prior to five and one-half or six months (ca. 30 cm. CH) and a constant and more rapid growth from that time to birth; 2) brain-stem and cord growth, which proceeds comparatively rapidly previous to the sixth fetal month and comparatively slowly thereafter, and, 3) cerebellar growth, which is characterized by a slow rate of growth prior to the seventh fetal month and by an extremely rapid rate of increase thereafter.


56 AMERICAN ASSOCIATION OF ANATOMISTS

25. Hematological and respiratory conditions in the larval stages of the lungless amphibians, Batrachoseps attenuates and Aneides lugubris. V. E. Emmel, University of California.

In attempting to correlate the remarkable occurrence of non-nucleated erythrocytes in Batrachoseps attenuates (Am. Jour. Anat,, vol. 16, p. 180; Anat. Rec, vol. 18, p. 232) with physiological factors, a comparative study was undertaken between this animal and Aneides lugubris. Both amphibians are lungless, have similar environments, but differ widely hematologically. It became necessary to carry the investigation into the larval stages. We were fortunate in securing one set of eggs for each species. A number of larval animals were removed from the egg before hatching and blood preparations made. In the larval Aneides all erythrocytes were nucleated, but in the larval Batrachoseps, on the contrary, non-nucleated erythrocytes were almost as abundant as in the adult.

It thus becomes evident that whatever physiological factors may be responsible for the marked hematological differences in these two species, they must be already operative before hatching. The larval respiratory gill structures show striking differences. Aneides has a very broad, three-lobcd, leaf-like gill membrane, permeated by a complex capillary network. Batrachoseps has a simple, slender, three-fingered gill structure, traversed by a single vascular loop for each finger-like process. In Aneides the blood corpuscles pass th'ough the gill capillaries in a single file, whereas in Batrachoseps the blood is carried through each vascular loop as a column of corpuscles in the manner of a small arteriole. In contrast to Aneides, therefore, we have in the larval Batrachoseps a respiratory mechanism relatively deficient in capillary exposure of the blood. This condition is apparently compensated for by the increased oxidation efficiency of the thin non-nucleated erythrocytic discs, thus furnishing a phylogenetic precursor of the erythrocytic efficiency finally attained in mammals.

(Further studies on the physiology of reproduction include abstracts 26 to 34-)

26. Proportio7i of ova producing full-term young in the rat. Joseph A. Long and Herbert M. Evans, University of California.

We are beginning to appreciate the widespread and customary occurrence of departures from perfect functioning of the mammalian reproductive apparatus — departures which reduce fertility. These may be due to fault with ovary, tube, or uterus. They are occurring continually. During the last three years we have recorded the number of young in 625 litters of the rat. The average lies between six and seven. During this period of time fifty animals were sacrificed within one day after ovulation and at least one oviduct and ovary cut serially. In all instances the eggs from this ovulation were encountered in the tube and were enumerated. An average was found of 4.8 eggs in each oviduct or 9.6 eggs per ovulation. Other material in which the eggs could not be enumerated with reliability, but in which the corpora lutea of a single ovulation could be counted, was studied. This showed that five corpora per ovary or ten per ovulation represented the average. The animals from which data were secured concerning the number of eggs or corpora were treated in every respect as to food, cage space, etc., identically with the animals in which the number of litter young was


PROCEEDINGS 57

recorded. They were also in many cases litter mates of such animals. Evidently, then, under these conditions nine or ten ova are represented by only six or seven offspring carried to term.

27. On the production of the condition of 'pseudopregnancy' by infertile coilvs or mechanical stimulation of the cervical canal in the rat. Joseph A. Long and Herbert M. Evans, University of California.

We have previously shown that the advent of the next oestrus is delaj^ed when the rat is allowed to mate with a vasectomized male or when the cervical canal is stimulated by the momentary insertion of a small glass rod. This pause, which we have proved to result from delayed ovulation, may be due either to some sort of direct repression of follicular growth or to a continuance of life of the corpora lutea which in the case of cattle have apparently been shown to hold off follicular growth and oestrus. The corpora lutea in these cases come to resemble those of pregnane}'. As we have previously explained, we are to understand this remarkable response as a contrivance to insure implantation. The fact that deciduoma are difficult to produce during normal oestrous cycles, but can be produced after cervical stimulation, is in strict harmony with the idea that changes are thereby provoked which facilitate implantation. We may suppose something has occurred to ' activate' the corpora lutea. The corpora are affected through humoral paths, since these phenomena all occur with the transplanted ovary. But nervous pathways are probably concerned in initiating the change, for the products of abrasion of the cervical mucosa do not themselves cause these changes (Freyer; see below). The designation 'pseudopregnancy' is justified on further grounds than because of the prolongation of life span of the corpora lutea. Most striking is a change in the character of the vaginal epithelial mucosa. In pregnancy the vaginal mucosa becomes a high stratified epithelium, but with its surface cells columnar instead of squamous in type. Furthermore there ensues a characteristic vacuolization of its middle cell laj^ers, a phenomenon beginning about the tenth day of gestation and reaching its greatest expression on the sixteenth day. These changes are inaugurated in the vaginal mucosa ten or more daj's after mechanical stimulation of the cervical canal.

28. On the cause of the effects produced by stimulation of the cervical canal in the rat. M. G. Freyer (introduced by H. M. Evans), University of California. The delay in the appearance of the next oestrus and the condition of so-called

pseudopregnancy produced by mechanical stimulation of the cervical canal in the rat has been shown by Long and Evans to take place in animals in which ovarian transplantation has recently been carried out. We can, hence, not refer this effect to the nervous connections of the ovary itself. It seemed possible that the slight injury to the cervical epithelium might lead to hormonal products which when absorbed and reaching the circulation thus affect the ovary directly or indirectly by means of some other endocrine gland.

At the suggestion of Doctors Evans and Long, six careful experiments were carried out in order to test this point. Epithelial scrapings were made from the lower portions of the cervical canal of six animals which were in the pro-oestrous period or at the transition between pro-oestrus and oestrus. This material, obtained under aseptic precautions, was immediately injected into the perito


58 AMERICAN ASSOCIATION OF ANATOMISTS

neal cavity of six other animals which happened to be at the same stage of the oestrous cycle. The succeeding oestrous cycles in the recipient animals were of normal duration. None of the characteristic effects of cervical stimulation were obtained. It would hence appear that the initial part of this mechanism is actually mediated by nerve impulses which, however, produce humoral changes so that the corpora lutea of recently transplanted ovaries, which can only be reached by the blood stream, are in some way invigorated and continued in function.

29. A characteristic histology of the vaginal mucosa during lactation. Joseph A. Long and Herbert M. Evans, University of California.

During lactation the vaginal smear in the rat resembles closely the picture found during the dioestrous interval of the normal oestrous cycle, i.e., it consists of polymorphonuclear leucocytes and a variable content of irregularly sized epithelial cells. Nevertheless, the histology of the vaginal mucosa at this time differs widely from that found in the dioestrous pause. We have previously established the fact that ovulation does not occur during lactation. Ovulation is always heralded by characteristic changes in the structure of the vaginal mucosa and also in the vaginal smear. In both pregnancy and lactation ovarian function is manifested by actively secreting corpora lutea which in turn may be viewed as repressing all follicular growth and activity. We have shown in the preceding section that a characteristic vaginal histology occurs throughout gestation. It is also a fact that during gestation the vaginal smear resembles that of the normal dioestrous pause. Similarly during lactation characteristic changes occur in the vaginal mucosal histology without changes in the smear. The epithelium in one respect resembles that found in pregnancy in that it possesses a surface layer of cylindrical cells. But the gravid vaginal mucosa is high, that of lactation low. While on the second day of suckling this mucous membrane may consist of four or five cell layers, by the fourth day more than three layers are seldom encountered, and on the sixteenth day, when lactation may be assumed to be at its height, most of the mucosa consists of but two cell layers, the superficial of which is constituted by cubical or low cylindrical elements. The strict dependence of this characteristic epithelium upon the performance of the mammary glands, which divert and limit ovarian function to the corpora lutea, is illustrated in the most striking way when the young are removed. Within forty-eight hours after removal of the young the low columnar mucosa of lactation gives place to a high, stratified squamous epithelium.

30. On the production of deciduomata during lactation. Joseph A. Long and Herbert M. Evans, University of California.

Our preliminary experiments seemed to indicate that deciduoma were not easily produced by the contact of foreign bodies with the uterine mucosa during lactation. We were consequently under the impression that the rarity of conception during lactation might be referable to an unfavorable implantation reaction in some way associated with lactation. We have continued our operations upon the uterus during lactation. Typical deciduomata can be produced when the procedure is carried out at any time after the fourth day of lactation and the animal sacrificed one week after the operation. It is consequently neces


PROCEEDINGS 59

sary to refer the well-known comparative immunity from a second gestation which characterizes the early period of lactation in all animals, to the lack of ovarian changes associated with both heat and ovulation, not to difficulties in implantation of ova. The existence of a vigorous dcciduoma reaction during lactation when uterine atrophy normally occurs would appear to establish conclusively the relation of this response to the existence of functional corpora lutea, for in all conditions in which functional corpora are present the response can be elicited.

31. Cijclic changes in the manmiary gland of the rat associated voilh the oestrous cycle. Monroe Sutter (introduced by H. M. Evans), University of California.

The exact mechanism responsible for £he assumption of function on the part of the mammary gland has received a considerable amount of attention during the last few years. Although an indirect nervous connection between mammae and uterus exists (influence of suckling on uterine contractions), it has been generally assumed that the development of the mammary apparatus is due to hormonal influences. As is well known, these hormones have been variously supposed to come from corpus luteum, placenta, or foetus. I have been encouraged by Doctors Evans and Long to study the changes which may be observed in the mammary glands of virgin female rats at various steps in the oestrous cycle. The study of sections was eventually abandoned and gross mounts were made of spreads of the entire glands which had been stained and cleared.

The following conditions have been detected: Toward the end of the prooestrous stage (stage of Long and Evans) the mammary tree exhibits long, slender branches which have a few almost naked twigs projecting from them. Close inspection reveals that there are many minute bud-like processes on the twigs and on the main branches at infrequent intervals. In the next stage, oestrus (stage 1 of Long and Evans), when cornified epithelial cells are found in the vaginal smear, undoubted evidence occurs of pronounced growth in the mammary tree. The small buds on the mammarj- twigs have sprouted out to varying degrees and new ones have appeared. Instead of appearing generally smooth and naked, the branches and twigs are irregular and covered with numerous projecting buds. The size and shape of the branches vary greatly from branch to branch and in a given branch. This great variability appears to be one of the most marked characteristics of rapid growth. By the time leucocytes have appeared in the vaginal smear, evidences of further growth in the mammary tree can be seen in the increasing complexity of the secondary branches. By this time we know that ovulation has normally occurred and young corpora lutea have been formed. The end branchings of the mammary tree often form transparent bulb-like projections which vary greatly in shape and size. This complexity of the tree and some slower growth of it undoubtedh' continue until near the nest pro-oestrous stage when, possibly due to degeneration of the corpora lutea, regression occurs.

There is thus a regular cycle of growth changes imposed upon the mammary ducts, and although these are undoubtedly accelerated and are maintained by the corpora lutea, they may be detected and are quite marked before the corpora are formed.


60 AMERICAN ASSOCIATION OF ANATOMISTS

52. On the rapid maturation of the ovary by trans-plantation of the youthful gonad to adults. Joseph A. Long and Herbert M. Evans, University of California. In order to determine whether we could produce an experimental precocitj^ in

the development of the remainder of the reproductive sj^stem, we attempted to transplant adult ovaries into young animals. As a matter of fact, an exchange of ovaries was carried out between immature animals from twenty to thirty days of age and adults between five and six months of age. The adult grafts succumbed, but in every instance the immature ovaries were vascularized and grew rapidly, although these also in some instances did not continue to function. It is, however, remarkable that in all instances at least one set of Graafian follicles and corpora lutea were produced by the infantile ovaries in adult hosts. Furthermore, these changes took place in from six to eight days and brought on typical oestrus of the adult host as seen by changes in the vaginal smear, behavior, etc. It is apparent that endocrine influences of the adult tissues are responsible for provoking this sudden maturation of the sex gland, which normally occurs from one to two months later.

53. The method of opening of the vagina in the rat. K. O. Haldeman (introduced by H. M. Evans), University of California.

At birth the lumen of the vagina extends caudal to within 1.2 mm. of the external surface of the body. The structure closing the vagina consists of a solid, branching core of stratified squamous epithelium surrounded by compact connective tissue. This condition persists until, at about the age of thirty to forty days, several centers of cornification appear in this epithelial core and vesicles containing desquamated cornified material and leucocytes are formed. The vesicles enlarge and coalesce so as to form a lumen through the epithelial core. The first external sign of impending opening is a turgescence and wrinkling of the future lips of the vagina. Occasionally a median cord extends dorsoventrally across the vaginal orifice for several days after opening. Frequently a plug of cornified material protrudes from the opening soon after it is established. Sections through the vaginae prior to their opening in animals older than thirty days showed large masses of cornified material, non-cornified cells, and leucocytes in the lumen near its distal end. In some cases small areas of the vaginal mucosa were covered with cornified epithelium. Five cases were studied to determine whether or not ovulation had occurred, and in no instance was this a fact. These isolated patches of epithelial cornification must not be confused with the complete cornified transformation of the vaginal mucosa accompanying oestrus.

54. On the association of continued cornification of the vaginal mucosa irith the presence of large vesicles in the ovary and the absence of corpus formation. Herbert M. Evans and Joseph A. Long, University of California.

It has already been shown that in the normal oestrous cycle of the rat cornification changes in the vaginal mucosa are associated with the enlargement and maturation of follicles and that these changes cease at about the time of ovulation. Normally the cornified stage lasts about thirty hours.

As a rare anomaly (seven cases in about 800 rats) cornification of the vaginal mucosa may be greatly prolonged; instances of 2, 3, 5, 7, 11, 11, and even 21 days


PROCEEDINGS Gl

have been observed. In one case in which cornification had persisted for five days and in two cases of eleven days the animals were tested and oestrus found to be still present. All of the seven rats were killed while this phenomenon was still in progress, and the ovaries examined in serial section. The most striking thing about them was the presence of large, fluid-filled vesicles, many of these possessing a thick, apparently healthy granulosa layer which together with the basement membrane is invaginated at many points by blood-vessels and containing what appeared to be normal eggs. Others were clearly undergoing degeneration, leading to the formation of large, thin-walled vesicles devoid of ova. In addition, the ovaries were notable by reason of the absence of normal healthy corpora lutea, those present being apparently in process of degeneration — quite markedly so in the one case of twenty-one days.

We have observed similar long cornified stages in the vaginal smears of two cases in which the ovaries were transplanted to the rectus muscle and in which also the ovarian findings resembled the above. This fact would appear to support convincingly the idea that these ovarian changes produce their effects on the vagina through humoral rather than nervous pathways.

{Experiments on the endocrine relations of the ovary in the rat include abstracts

35 to 38.)

35. The effect of thyroid feeding on the oestrous cycle of the rat. Herbert M. Evans and Joseph A. Long, University of California.

Thyroid obtained daily from freshly slaughtered beeves was fed in doses varying from I gram to an entire half gland. The rats used for feeding as also those for controls were selected from a large stock because they exhibited approximately regular four-day cycles.

In all cases thyroid feeding was accompanied by an increased consumption of food, but decrease in body weight. On the one hand, when the doses were larger (j to I gland) loss in body weight was pronounced and some animals succumbed, the cycle being greatly lengthened or inhibited altogether. On the other hand, when the doses varied from J to U grams daily, amounts also sufficient to produce loss of weight with increased consumption of food, the oestrous cycles were usually not greatly disturbed. There consequently do not appear to be specific effects of thyroid substance on the oestrous cycle.

36. The effect of thyroidectomy on the oestrous cycle of the rat. Herbert M. Evans and Joseph A. Long, University of California.

Both thyroids were removed from three groups of rats which lived a long postoperative life: thirty-one adults, seventeen young rats 37 to 54 days of age, and eleven suckling ones. In all cases there was no doubt but that by far the largest part of the thyroid was excised, and in the youngest rats the operation was performed under binocular microscopes. The mortality from the operation is low. In the case of the adults the operation was usually followed by a pause in the oestrous cycles of 6 to 27 days, but in turn succeeded by normal oestrous cycles, about twenty of which were observed.

The operations on both the young and suckling animals influenced appreciably neither the time of maturity nor the lengths of oestrous cycles. Several of the second group after reaching an age of several months were autopsied and


62 AMERICAN ASSOCIATION OF ANATOMISTS

found to possess what appeared to be lobes of regenerated thyroid tissue in many cases almost of the size of normal glands. Sections found these to be thyroids which had regenerated in spite of the effort which had been taken to secure complete ablation.

37. The effect of feeding the anterior lobe of the hypophysis on the oestrous cycle of

the rat. Herbert M. Evans and Joseph A. Long, University of California.

Four sets of experiments were carried on, in two of which fresh glands were fed and in two dried hypophysis from Armour & Co. and from Parke-Davis & Co. In all cases the feeding was begun at weaning, on the twentj'^ -first to twenty-third day, litter mates being used as controls. Daily observations were made to determine the opening of the vagina and cyclical changes in the vaginal smear. A total of fifty-five rats was used for the experiments and fifty-four for controls.

The anterior lobes were dissected from the glands of freshly slaughtered cattle and were ground, weighed, and fed within six hours of slaughtering. A half gram was given each rat, which had been isolated in a clean metal box where it could be seen that the total amount given was consumed, after which the animal was returned to its cage and given ordinary food. In one set the controls were not fed differently from their mates except for the hypophysis; but in the other set the controls were given in addition \ gram of raw liver daily to offset the possible nutritive value of the fresh hypophysis. Each rat was weighed at intervals of four days. In both sets the hypophysis-fed animals and controls showed neither significant differences in growth nor in the age of maturity and lengths of subsequent oestrous cycles. In the case of ten adult rats the total food intake was limited to 6 to 10 grams of the fresh anterior lobe and rolled barley. Their oestrous cycles (ten to twenty of which were observed) were not sensibly altered.

Similar tests were conducted with the dried commercial substance, except that no controls were given fresh liver. But for the fact that large doses could not be given without producing intestinal disturbances, the results were not substantiallj' different from those given above.

38. The effect of the anterior lobe administered intraperitoneally upon growth,

maturity, and oestrous cycles of the rat. Herbert M. Evans and Joseph A.

Long, University of California.

The anterior lobes were dissected from fresh glands, were immersed five minutes in 30 per cent alcohol, rinsed thoroughly in sterile Locke's solution, triturated with a small amount of sand, and centrifuged for about half an hour, care being taken to carry out all manipulations aseptically. The supernatant fluid from centrifuging was injected into the peritoneal cavity in amounts from i to 1 cc, according to the age of the rat, the first dose being given at an age of about fourteen days. At the beginning a similarly obtained fluid substance from liver was given some controls, but soon discontinued because of its toxic effect. Every animal was weighed at intervals of five days, beginning with the twentieth day of age. To date daily observations have been carried to the eightieth day. The subjoined table shows a greater rate of growth of the experimental animals as compared with their controls, a disparity which is increasing.

At the same time the effect of the anterior lobe has been to repress sexual development by delaying .sexual maturity and lengthening the oestous cycles, in some cases oestrus being entirely inhibited.


PROCEEDINGS


63


In the case of five adult rats with previously regular four-day cycles, doses of 1 to 2 cc. of the anterior lobe fluid substance caused an immediate cessation of the four-day rhythm, the smaller doses permitting oestrus to recur at longer intervals, the larger inhibiting it altogether. These results are in marked contrast to the lack of effect produced by oral administration of the anterior hypophysis. As far as the influence on sex function is concerned, they are in marked contrast to prevalent opinion.


AGE


38 EXPERIMENTAL ANIMALS


38 LITTER MATE CONTROLS


days


grams


grams


14


20.2


19.02


20


31.6


33.14


25


48.6


46.2


30


61.7


60.0


35


80.6


70.7


40


95.6


86.2


45


117.6


109.0


50


140.8


126.1


55


159.5


139.25


60


177.0


153.3


65


197.2


165.6


70


214.5


173.7


75


227.8


183.5


39. The digestion and assimilation of fatty food as determined by the aid of the

dark-field microscope, and a fat-soluble dye {American sudan). Simon H. Gage,

Cornell University.

The findings on the above reported at the last meeting of the Association have been repeatedly verified on people of various ages and on animals of widely different species. That is, with a dark-field microscope one can determine by the number of particles (chylomicrons) present: a) Avhether the fat taken with the food is being digested and absorbed; b) the time required for the process; c) the comparative digestibility of a given fat by different individuals and different species of animals; d) the comparative digestibility of different fats by the same individual or animal.

In the further study of the subject it has been found not only possible to determine the appearance, increase, diminution, and disappearance of the fat particles (chylomicrons) in the blood or chyle by the dark-field microscope, but with the naked eye it has been easy to follow the digested fat from the intestines to the lacteals, to the lymph nodes and to the cisterna chyli, and through the thoracic duct to the blood-vessels, and in the blood-vessels to all parts of the body. This was made possible by the use of a fat-soluble dye (American sudan), which when once dissolved by the fat, sticks so tight to it that it never lets go through all the processes of digestion, although they may involve splitting the fats into fatty acids and glycerin or even the formation of soaps and their absorption and res\^nthesization by the intestinal epithelium. The color serves as a label, so to speak,


64 AAIERICAN ASSOCIATION OF ANATOMISTS

and enables one to follow it in all its wanderings, and to see where it is finally deposited when assimilated.

Contrary to the general assumption that the fat is placed in temporary storage when it disappears from the blood, and is only very slowly and after considerable time finally deposited in the permanent fat reservoirs or adipose tissue, it was found that the fat was very quickly deposited in the adipose tissue of the entire bodj', but especially and most markedly in the adipose tissue of the omentum, mesenteries, and kidneys. The pink-stained fat is abundantly and easily recovered from the chyle, the blood and the adipose tissue thus leaving no doubt as to the nature of the pink substance.

40. Cinematomicrographij of serial sections. W. F. Schreiber, Stacy R. Guild,

and L. G. Herrmann, University of Michigan.

By combining photomicrographic and cinematographic methods a film has been produced on which are pictures at a low magnification of all the serial sections of an embryo, with the individual pictures so oriented with reference to each other that, when projected onto a screen by the usual moving-picture apparatus, the images overlap in much the same way that the individual wax plates used in making a model are overlapped. Whereas the successive pictures of an ordinary film gave temporal impressions, the attempt here is to give spatial impressions. It is hoped that the method will be useful as an aid in the teaching of embryology to large groups of students, especially as a supplement to the study of serial sections by the individual members of the group. The projection of the film available at the present time will constitute the major part of the presentation of this paper.

il. The Jiervons system as a factor in the resistance of albino rats to ■parathyroidectomy. Frederick S. Hammett (introduced by H. H. Donaldson), The Wistar Institute of Anatomy and Biology.

Studies made on the susceptibility of albino rats to acute parathyroid tetany resulting in death showed that animals which had been gentled by petting and handling were less frequently affected by removal of the parathyroids than were rats lacking this treatment. Three hundred and four rats were operated. In one group the parathyroids alone were removed, in another, the entire thyroid apparatus, and in a third the thyroid apparatus was removed in two stages, at an interval of two weeks. About 13 per cent of the gentled rats died in acute tetany after these procedures, while about 78 per cent of the not gentled rats died within forty-eight hours after operation. These results are taken to indicate that the gentling induces a condition in the nervous system such that the demand of the organism for the parathyroid secretion is lessened to the point where the rat survives though the secretion is lacking. Since the condition of high neuromuscular tension present in theratesnotgentledimpliesaheightened metabolism of that phase of activity concerned with muscle tone, it is possible that in these rats there is thus produced a greater amount of some toxic by-product than in those gentled, and that removal of the parathyroids also removes the mechanism for the destruction or neutralization of this toxic compound and the animals consequently succumb to the excess of the hypothetical compounds so formed.


PROCEEDINGS 65

42. An ada-ptation of the fire-assay method for the determination of gold and silver in animal tissues. Samuel Hanson (introduced by H. M. Evans), University of California.

Methods hitherto employed in quantitative determination of gold and silver in animal tissues have not been entirely advantageous. The titration method of Voigt for the estimation of silver is inconvenient and its accuracy uncertain. The electrolytic method of Caldwell and Leavell is complicated and time-consuming. The well-known fire-assay method may be adapted to determine very small quantities of gold and silver in animal tissues with a high degree of accuracy. The tissue for estimation is dried and pulverized. Two grams of the powdered tissue is transferred to a glazed paper and thoroughly mixed with 60 grams of silver-tested litharge, 20 grams of sodium carbonate, and 15 grams of silica. The mixture is transferred to a clay crucible and covered with 10 grams of sodium carbonate. The charge is fused in the muffle at a high temperature until no suspended droplets of lead are seen. The stage is usually reached in thirty minutes. The fused material is next poured into a conical iron mold, the lead settling on the bottom of the mold, while the fused material, or slag, collects at the top. If the fusion has been properly carried out, the slag is transparent and free from particles of lead or carbon. The slag is removed and the lead hammered into the form of a cube with blunted corners. Such a lead button should weigh between 25 and 30 grams and is placed in a red-hot bone-ash cupel in the gas or electric furnace and the cupellation continued at a temperature sufficiently high to prevent heavy fumes. The cupellation may be regarded as completed when the residue suddenly loses its brightness and appears as a small bead. The bead is weighed on the assay balance to 0.01 of a milligram. After weighing the bead, the silver, if present, is dissolved and the bead reweighed. The latter weight, of course, represents the quantity of gold present, if both gold and silver are present, while the difference between the two weights corresponds to the amount of silver.

43. On the rapidity of absorption of colloidal gold from the peritoneal cavity. Samuel Hanson (introduced by H. M. Evans), University of California.

The phenomena of absorption of dialyzable substances from the peritoneal cavity have been extensively investigated. Phenolsulphonephthalein, for example, is absorbed from the peritoneal cavity at a known rate, evidently chiefly by way of the blood capillaries, and the mechanism of its absorption can probably be satisfactorily explained by assuming that the physical processes of osmosis and filtration are operative. In the case of the absorption of colloids and suspensoids, however, the situation is different. The experimental work done with this class of substances, with the exception of the recent paper by Cunningham and Shipley, is almost exclusively qualitative. The absorption of colloidal gold furnishes an excellent opportunity to obtain quantitative data in this field, for gold may be estimated in tissues with high accuracy (see above), and its colloidal solution made according to the method of Paal is stable and largely physiologically inert. Solutions estimated to contain 1 per cent metallic gold in physiological saline were used. Injections were made into the peritoneal cavity of rats, 1 mgm. of metallic gold per 10 grams of body weight being given. After various intervals the animals were sacrificed and the

THE ANATOMICAL RECORD, VOL. 21, NO. 1


66 AMERICAN ASSOCIATION OF ANATOMISTS

amounts of gold found in the liver determined by the fire-assaj- method given above. The rapidity of absorption of the gold as determined by its deposition in the liver is remarkable, 8 per cent of the amount injected being found at the end of the first hour and 22 per cent at the end of two hours. According to Dandy and Rowntree, about 50 per cent of phenolsulphonephthalein injected intraperitoneally is absorbed within one hour. This substance diffuses readily through animal membranes and its smallest particles are probably represented by the molecular dimension; the size of the gold particles is in contrast very many fold greater, yet they traverse the peritoneal boundary at a rate at least one-sixth as rapid.

U. The developtnent of the balancer in Amblystoma. Ross G. Harrison, Yale

University.

As shown by Bell in Diemyctylus, the development of the balancer is determined by a patch of differentiated ectoderm overlying the mandibular region. When this ectoderm is transplanted to other regions of the embryo in Ambh^stoma punctatum, even as early as the medullary-plate stage, a normally constituted, though somewhat smaller, balancer develops. If it is replaced by ectoderm from the trunk, the front of the head, or from the gill region, no balancer develops. Removal of the mandibular mesoderm does not affect the development of the balancer, if the ectoderm is healed back in place, nor does the removal of the ganglion crest (experiment of L. S. Stone), though cells from the latter lie directly under the base of the outgrowing organ and normally probably provide its mesodermal C(}re. Amblystoma tigrinum lacks balancers. If, however, proper ectoderm of A. punctatum is transplanted to the former species, a normal balancer with mesenchyme and blood circulation develops. The reciprocal operation apparently suppresses the balancer, though only one experiment has given this result. Owing to faulty placement of the graft in others, regeneration from the host occurred. The peculiar membrane which supports the balancer develops in the strange as well as in the normal location. Its staining qualities and the imbedding of its base in mesenchyme might lead one to regard it as a dermal bone, as Latta has done. However, it is never formed except beneath the specific balancer ectoderm, and the evidence favors its interpretation as a basement membrane.

45. Amiiosis in ciliated cells. Frank Helvestine, Jr. (introduced by H. E.

Jordan), University of Virginia.

In 1898 V. Lenhossek and Henneguy independently expressed the opinion that the basal bodies found in ciliated cells are derivatives of the centrosome. The corollary of this hypothesis, namely, that on account of the preemption of the centrosome in the formation of basal granules, ciliated cells must necessarily proliferate by amitosis, was later expressed by Jordan ('13), and he supported this conclusion by data derived from a comparative study of the ciliated epithelium in the ductili pffcrentes and epididymes of a number of vertebrates.

Saguchi ('17) confirms Jordan's results as regards vertebrates, but states that in invertebrates mitosis is the exclusive mode of division of ciliated cells. He describes cells undergoing karyokinesis as either not having cilia or as losing their cilia before the process of division takes place. Saguchi concludes from his obser


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rations that basal bodies and cilia are derived from mitochondria. His descriptions and illustrations do not bear out this conclusion, but rather add to the evidence of a centrosomal origin of the basal bodies.

In mj' material of the gills of the fresh-water mussel, Cyclas, no relationship between mitochondria and basal bodies, other than spatial, is discernible. Indirect evidence supports the view of the derivation of the basal bodies from the centrosome. In this form certain ciliated cells divide extensively only by amitosis. Saguchi admits that cells of ciliated epithelium dividing by mitosis possess no cilia at the time of division and my material confirms this observation. Such cells cannot properly be called ciliated cells and it can accordingly not accurately be said that ciliated cells divide bj' mitosis.

In view of the agreement between Jordan ('13) and Saguchi ('17) regarding an exclusively direct method of division in ciliated cells of vertebrates, and Saguchi's failure to find in invertebrates any cells with cilia in indirect division, and my demonstration of extensive amitotic divisions in ciliated cells of Cyclas, the general conclusion seems warranted that ciliated cells both in vertebrates and in invertebrates divide only by amitosis.

46. Develo-pment of the innoviinaie artery in the pig. Chester H. Heuser, Johns Hopkins Medical School.

In a closely graded series of injected embryos ranging in length from 3.8 mm. to 40 mm. which was prepared for a study of the transformations of the aortic arches and the related vessels, the development of the innominate artery can be followed from its primitive condition until its adult form is attained. The cephalic border of the bulbous ventral aorta in the 7-mm. embryo gives rise to the large third aortic arches and the rudimentary external carotid arteries. In embryos of S mm. the ventral ends of the third arches carry the external carotids so that the common carotids are alreadj' indicated. In succeeding stages beyond 8 mm. the ventral portions of the third and fourth arches are united into common trunks which gradually increase in length. This trunk is especially long on the right side and is a part of the innominate arterj^, but as the arch of the aorta becomes established from the left fourth arch the left common carotid becomes shifted over so that it arises also from the innominate. This condition can be seen in stages of about 21 mm. In older embryos the connections remain the same, but the innominate artery increases greatly in length, as seen in stages measuring 40 mm. or more.

47. Extirpation and transplantation of thymi in larvae of Rana pipiens. Margaret Morris Hoskins, Medical College of Virginia.

The operations were performed by E. R. Hoskins in the spring of 1919 and the report is based on a study of preserved material. Records were kept of the growth and development of the larvae and showed no effect from the experiments in this respect. The operations were of three types: complete and unilateral extirpation of thymi and transplantation of thymic tissue from one larva to another. The grafts grow well and have the appearance of normal thymic tissue. The effect of the operations on the thymi, the spleen, and on the endocrine glands has been studied from dissections and from histological preparations. When one thvmus is removed there is no compensatory hypertrophy of


68 AMERICAN ASSOCIATION OF ANATOMISTS

the remaining one, and the engrafting of thymic tissue does not affect the thymi of the host. None of the operations affects the spleen in size of appearance. The gonads, thyroids, and parathyroids also remain unchanged. In some instances the hypophyses of thymectomized larvae appear to be hypertrophied, but this is not always the case. Histologically the hj'pophyses of the operated animals are normal.

48. Embryonic myeloschisis. (Stereo-lantern.) N. William Ingalls, School of Medicine, Western Reserve University.

The three human embryos considered naturally fall into a series of increasing teratological and pathological severity. This also applies to the embryonic adnexa. No. 83, G. L., ca. 7 mm., condition fair, chorion quite large, villi large and numerous but somewhat altered, amnion thickened, magma excessive, cord and yolk sac small, vessels indefinite. Sacral myeloschisis extending over 2.5 mm. on summit of sacral convexity, neural folds everted, prominent and sharply defined. No. 288, G. L., ca. 12 mm., condition poor, color not very good, chorion of fair size but thin, villi not well developed, hydramnios, no exocoelom, cord small, no yolk sac found, only traces of vessels. Medullary defect measures 2.5 X 4 mm. , extending from thoracic into sacral region. Area involved is spread out on dorsum of embryo, its surface very slightly elevated, margins irregular. In No. 46 the disturbance has been much more severe. G. L. 14.5 mm. , distinctly pathological, color muddy and opaque; chorion large and haemorrhagic, villi very short and scattered, hydramnios, no exocoelom, amniotic fluid slightly turbid and viscid, neither vessels nor yolk sac to be seen, cord short and markedly distended. Extensive defect involves most of cord, secondary loss of substance; marked encephalic malformation, head very small, eyes approximated, mouth gaping, nasal and palatal deficiencies. General anasarca of embryo.

49. The effects of various types of inanition upon growth and developjnent, with special reference to the skeleton. C. M. Jackson, University of Minnesota. According to Liebig's 'law of the minimum,' as applied to animal growth by

Bunge and by Osborne and Mendel for mineral and protein factors of the diet, the deficiency of any essential factor results in failure of the growth of the body as a whole, and not in the production of abnormal tissues. However, during inanition of various types there occurs a malcorrelated growth, certain organs increasing abnormally, others decreasing, with retarded or stationary body weight.

During underfeeding of young rats on a balanced diet (deficient in calories), this disproportionate growth affects practically all organs of the body, the extent varying widely in different organs ; also according to age, and length and intensity of the inanition (Jackson, Stewart, Barry). Persistent skeletal growth has likewise been observed by other investigators in underfed calves, puppies, rats, and malnourished infants.

In rats on qualitatively inadequate protein diets, Osborne and Mendel found skeletal retardation proportional to that of the whole body; but more recently Mendel and Judson ('16) found persistent skeletal growth in mice. Kudo ('21) finds markedly persistent skeletal growth in rats with restricted water supply.


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Absence of essential salts results in disordered or inhibited skeletal growth, in invertebrates (sea-urchin, sponges) as well as various mammals. With calcium-poor diets, the body weight may continue increasing, while the skeleton is retarded, with 'pseudorachitic osteoporosis.' True rachitis apparently depends upon a deficiency in ' fat-soluble A' vitamine. Phosphorus deficiency likewise retards skeletal development, with histological resemblance to scorbutus (which, however, is also due to vitamine deficiency).

50. Studies of lymph nodes. II. Response of hjmph nodes to irritation. (Lantern.) Thesle T. Job, Loyola University School of Medicine.

By injecting subcutaneously India ink in either distilled water or weak solutions of ammonium hydroxide, a condition simulating a low grade or a virulent infection may be initiated. By this method a less complicated picture is obtained but, nevertheless, just as true as when cancer cells or bacteria are injected. Thus it can be demonstrated that, in the case of ink in water, the granules are carried by phagocytes, mainly, to the first node in the drainage line. This node becomes progressively pigmented to a solid black. Then the second node in the drainage is pigmented, and so on. This being a non-irritative process, no new h^mphoid tissue is formed. If ink in ammonium h3'droxide be used — the ammonia being a strong irritant — the first node in the line of drainage is only partly pigmented before the second node begins to receive pigment ; the lymphat ic collateral circulation about the node is enhanced and an actual building up of new lymphoid tissue is begun. The significance of these results is pointed out and a practical application made.

51. On the origin and development of the posterior lymph hearts in anuran embryos. (Lantern.) Otto F. Kampmeier, College of Medicine, University of Illinois. The first evidence of the beginning of the posterior lymph heart on either side

is manifest in 10 to 11 mm. embryos (Bufo vulgaris) as an accumulation of mesenchymal cells around that part of the lateral lymphatic plexus situated just lateral to the posterior vertebral vein at the level of the eleventh spinal ganglion. By gradual distention and coalescence, the vessels of the lymphatic plexus within the area of mesench3"mal accumulation become transformed into a globular chamber, the posterior lymph heart. The lymph-heart anlage becomes temporarily separated from the surrounding lymphatic network, the number and position of the points of separation being relatively constant in different individuals. Two points of junction are reestablished between lymph heart and plexus, one situated on the dorsal and the other on the ventral side of the heart; later such points of entry are increased in number. The muscular coat of the lymph heart is developed from the cells of the original mesenchymal accumulation around the lymph heart plexus.

Before the efferent valve (between lymph heart and posterior vertebral vein) is formed, blood corpuscles are found in large number in the heart cavity. There is evidence that at times the embryonic posterior lymph heart itself may function as an haemopoietic center; certain it is that during its development, it, like other embryonic lymphatics, is haemophoric, that is, transports along with its lymph flow developing blood cells to the blood stream. Not only does the number of posterior lymph hearts differ among species of Anura, but it may also differ among members of the same species, and may even be different on the two sides of the same individual.


70 AMERICAN ASSOCIATION OF ANATOMISTS

62. Peripheral migration and distribution of medullary cells in the absence of spinal ganglia and dorsal nerve-roots in embryos of the chick. Albert Kuntz, Saint Louis University School of Medicine.

Embryos of the chick were subjected to an operative procedure at the close of the second day of incubation (forty-eight hours) by which the neural crests and the dorsal portions of the neural tube were destroyed throughout a series of successive segments. These embryos were allowed to live until the close of the fifth day of incubation. Ventral nerve-roots are present in all segments in which the motor niduli awere not destroyed. Cells of medullary origin are present in these nerve-roots and along the course of their fibers. Some of these cells advance along the visceral rami and give rise to ganglia of the sympathetic trunks, others become distributed along the nerve-fibers and give rise to neurilemma. In segments in which but a small ventral portion of the neural tube remains intact, even though ventral nerve-roots but no visceral rami are present, the primordia of the sympathetic trunks are absent.

53. Nerve terminations in the lung of the rabbit. (Lantern.) O. Larsell, Northwestern University.

Sensory nerve endings are found in the epithelium of the bronchial tree and its various subdivisions as far as and including the atria. These appear on anatomical grounds to consist of three types, probably receptive to different methods of stimulation. The most constant position in which sensory terminations are present is at the point of division of the various orders of branches of the bronchial tree. Motor terminations are also present, not only in the smooth muscle fibers of the bronchi and their branches, but in the pulmonary artery and its branches, including the arterioles. A few nerve fibers are also present in the tunica media of the pulmonary veins. The sensory innervation is by fairly large myelinated fibers from the vagus. The motor innervation of the bronchial musculature appears to be of the typical preganglionic and postganglionic arrangement. The preganglionic fibers terminate in characteristic pericellular networks about the cells of the intrapulmonary ganglia, and from these nerve cells processes are given off which pass to the smooth muscle bands, to terminate in relation to the unstriated muscle cells. The source of the fibers to the pulmonary vessels has not yet been determined.

54- The growth of the organs and systems of the single comb White Leghorn chick.

Homer B. Latimer, L^niversity of Minnesota.

In plotting the gross weight of the eighty-six chicks upon age in days (from day of hatching to 251 days) the resulting curves show three phases; first a slow initial rise, then a rapid increase, and later a second period of slow growth. The curve for the females begins to fall below that of the males, beginning at about seventy or eighty days. The curves of the different organs and systems may be placed in four groups as follows:

1. Those which tend to parallel the growth of the body as a whole, or the muscles, ligamentous skeleton, digestive tract, lungs, heart, kidneys, suprarenals, and integument. The curves of the percentage weights of these organs on the net body weight show a more or less rapid decline, with the exception of the musculature which increases from about 25 per cent up to nearly 50 per cent of the net body weight.


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2. This group is characterized by a rapid initial rise of the growth curve, followed by a slowing of the rate of growth. In this group are the brain and eyeballs and linear measurements (body length, etc.).

3. The ovary, oviduct, testes, and comb and wattles grow very slowly at first, followed by a rapid prepubertal rise, in both absolute and percentage weight.

4. The thymus and the feathers at first grow in weight a little more rapidly than the body, followed by a decrease in weight, both relative and absolute.

When the gross body weight is substituted for the age in days, the chief differences in the curves are a more precipitous rise at first and in some cases a loss of the second flatter part of the curve.

55. The description of the coats of blood vessels contained in Galen's De anatomicis administrationihus , Liv. VII., Cap. V. A comment on its accuracy. Frederic T. Lewis, Harvard Medical School.

The description is as follows: Venae totius corporis ex peculiari una constant tunica; nam exterior membrana ipsis nonnunquam obhaerescens, ubi colligari quibusdam aut fulciri ac contegi desiderant, illuc solum accedit. Arteriae vero duae peculiares tunicae existunt: exterior sane qualis venae est: interior autem crassitie hujus fere quintupla, insuper durior, in transversas fibras dissoluta; exterior autem, quam etiam venae obtinent, rectis fibris, et quibusdam mediocriter obliquis, transversis nullis, contexta est. Interior arteriae tunica crassa duraque ceu cutem quandam interna superficie continent, telae araneorum manifesto persimilem, in magnis quidem arteriis perspicuam, quam nonnulli tertiam arteriae tunicam statuunt: quarta vero alia peculiaris ei nulla est, sed veluti quibusdam venarum, ita quoque arteriis alicubi obhaerescit et circumtenditur membrana tenuis contegens aut affirmans aut connectans ipsas vicinis particulis.

56. The formation of vacuoles in the cells of tissue cultures owing to the lack of dextrose in the media. Margaret R. Lewis. Carnegie Laboratory of Embryology.

Cells cultivated in media lacking dextrose show numerous vacuoles in twentyfour to forty-eight hours, after w^hich degeneration rapidly ensues. When the usual amount of dextrose (0.25 per cent) is included in the media, the vacuolation, degeneration, and final death of the cells are retarded for several days. If a medium containing from 0.5 to 1 per cent dextrose is used, the cells continue in an apparently healthy condition for a much longer period of time, sometimes two or three weeks, during which vacuoles fail to appear. Ultimately, however, the cells in such cultures may exhibit vacuoles. Dextrose is an important part of the medium for tissue cultures, and it seems to be necessary in order to maintain the normal metabolism of the cells under the conditions of tissue cultures.

57. The characteristics of the various types of cells found in tissue cultures from chick embryos. Warren H. Lewis, Carnegie Laboratory of Embryology. Each type of cell that migrates out of the explant onto the coverslip does so in

a manner peculiar to its type. The blood cells and clasmatocytes pursue very irregular and uncertain paths, each cell retaining its complete independence, in that they rarely adhere together to form any sort of pattern. In marked contrast to these wandering cells are the ectodermal and endodermal cells which always migrate out in the form of a sheet or membrane, the borders of the cells


72 AMERICAN ASSOCIATION OF ANATOMISTS

adhering to their neighbors in more or less even lines. Intermediate between these two extremes are the mesenchyme, endothelial and smooth muscle cells which form loose reticuli, in that the cells tend to adhere to one another by their processes rather than by the cell borders. The cells of each type form, however, their own peculiar characteristic pattern of reticulum. Isolated ectodermal and endodermal cells occur and still more frequently isolated mesenchyme, endothelium and smooth muscle cells. Still different are the characteristic outgrowths of long multinucleated strands from the striated muscle and the long slender nerve fibers from both the sympathetic and central nervous systems. Both the muscle strands or buds and the nerve fibers have a tendency to form anastomosing plexuses, the nervous ones being more elaborate and complicated. The various other types of cells which migrate onto the coverglass do so each in a characteristic formation of characteristic cells. These characteristics both of the individual cells and of the types of growth are retained throughout the life-history of the culture, or until marked degeneration changes take place. There is no dedifferentiation after they have grown out on the coverslip, although cell division is frequent.

58. S77iooth muscle and endothelium in tissue cultures. Warren H. Lewis, Carnegie Laboratory of Embryology.

Smooth muscle from the amnion and endothelium from the sinusoids of the embryonic chick liver form a somewhat similar reticulum in the cultures. They resemble one another much more than they do the ordinary mesenchyme from the subcutaneous tissue. The smooth muscle cells have a rather thick homogeneous ectoplasm and in the living cell no indications of fibrillae are to be seen unless the cells are subjected to a sudden change. The fibrillae that have been occasionally observed under such conditions were gradually lost, the ectoplasm becoming homogeneous again. On fixation under the microscope the striae and fibrillae appear as the coagulation of the ectoplasm proceeds. The fibrillae are coagulation products of a peculiar kind of ectoplasm. They are not always parallel, but may in different parts of the spread-out cells run in groups at different angles. The peculiarity of ectoplasm which causes it to coagulate into fibrillae of varying sizes is probably a molecular thing, and it is to the latter that the contractile substance owes its peculiar properties. Our observations are in entire accord with those of Mrs. Lewis on smooth muscle.

Endothelial cells often show somewhat similar striae or fibrillae on fixation. The condition is never so marked as in smooth muscle, but it suggests that there is an unusual amount of contractile substance in endothelium which is interesting in connection with recent physiological work on the contraction of the capillaries by Dale, Krogh, Bayliss, and Hooker.

69. Preliminary remarks upon the Junctional variations of the normal human mammary gland. Joseph McFarland, University of Pennsylvania. In the study of cases of a morbid condition of the human mammary gland known as 'abnormal involution,' a variety of appearances were encountered that were very puzzling. The difficulty seemed to lie in uncertainty as to what was and was not to be regarded as normal, and part of the evolution and involution of the gland. Books and journals did little to help one out of the dilemma.


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Text-books of histology, for the most part, describe and illustrate the structure of the mammary tissue in such manner as to lead one to suppose that, except at the time of lactation, all glands look alike.

With a view of finding out what variations in structure and appearance the normal mammary gland presents, about 200 apparently normal glands were collected, sectioned, and studied. From this work it has become evident that a number of structural types will have to be established, and it is believed that in the future it will be necessary to call the attention of the student to each of these types, in order that he shall not later be surprised and confused by finding that the structure of a gland that he is called upon to examine in the pathological or hospital laboratory does not correspond with what he has been taught and shown as a student.

60. The influence of the lateral-line syste7n in the devclopmint of the skeleton. Roy L. AlooDiE, University of Illinois, College of Medicine.

The study of the lateral-line canals in ancient Amphibia and primitive fishes shows a definite correlation with certain peripheral osseous elements of the head. This fact suggests that during development there may be a relationship between the formation of the canals and the initiation of osseous development.

Young catfishes, Ameiurus nebulosus, were cleared by the potash method and the relationship of both lateral-line canals and developing skull bones was studied. It was found that the lateral-line canals were all laid down prior to the deposition of any osseous material, but those bones which touch on the canals were the latest of the cranial elements to form. This indicates that the lateralline canals have no influence on the initiation of osseous development, but that the canals do modifj^ the forrp of the bones which they touch. The factor which causes the initiation of osseous deposition must be looked for elsewhere.

61. On the specificity of regenerating limb-buds in adult newts. C. V. Morrill, Cornell University Medical College.

The present paper is a preliminary report on a series of transplantation experiments (still in progress) to test the specificity of regenerating limb-buds in the adult of the common spotted newt (Diemyctylus). The subdivisions of the problem are as follows: a) Will regenerating limb-buds retain their laterality if transplanted to opposite side of the body? h) Will a regenerating bud (e.g., from an anterior limb) retain its specificity if transplanted tj the stump of a different kind of limb (e.g., to a posterior limb stump)? c) Is there any observable difference between autoplastic and homoplastic transplantations?

For the purposes of the experiment, regenerating buds were transplanted when about one-eighth of an inch long and just beginning to show indications of digits. In order to test out the various possibilities outlined above, anterior limb-buds were transplanted to the stumps of posterior limbs of the same and of opposite sides, and posterior limb-buds to posterior stumps of opj)osite sides. In some cases the buds used were taken from the same individual (autoplastic), in other cases from a difTerent one (homoplastic). In this way seven different categories of experiments were made possible, though all have not yet been tested. The results in general show that in most cases the regenerating bud first loses most of its external and internal differentiation and becomes reduced


74 AMERICAN ASSOCIATION OF ANATOMISTS

to a conical knob consisting of a layer of epithelium and an internal mass of more or less indifferent cells. There is undoubtedly some mingling of the tissues of transplant and stump. Subsequently a redifferentiation takes place; the bud lengthens out again and digits appear. In all cases so far examined the original laterality of the bud seems to be entirely lost, that is, the transplant develops into a limb corresponding in this regard to its new site. Regarding anterior and posterior specificity, the results are not uniform. As a rule, the original specificity is lost, but in one case an anterior limb-bud transplanted to the stump of aposterior limb of the same side (homopleural), but on a different individual (homoplastic), developed into an anterior limb. Aside from the case just cited, no differences between autoplastic and homoplastic transplantations have as yet been detected, but the number of experiments is too small to warrant any conclusion. In all the types of experiments, reduplications occasionally appeared, as might be expected. Double limbs are of course the most common, but in two cases triple limbs developed. These are at present too young to interpret with certainty.

62. Studies on the mammary gland. VIII. Gross changes in the mammary gland in the female albino rat during the period of involution. Frank J. Myers and J. A. Myers, University of Minnesota.

Virgin animals of known age and weight were allowed to become pregnant, deliver, and nurse their young. In all cases the litters were weaned at the end of three weeks, after which the mammary glands of the mothers were collected at intervals ranging from six hours to five weeks. The glands were spread out on sheets of cork and cleaned according to the method previously described (Myers, '16). At the end of six hours the masses of glandular tissue are considerably enlarged. This enlargement which is probably due to the accumulation of milk continues through the forty-eight-hour stage. In the four-day stage the masses of glandular tissue have decreased considerably in size, while at the end of five days the glands are not more than one-half the size of those taken at forty-eight hours. In the stages taken at the end of two and three weeks the glands very closely simulate those of adult virgin animals. The most noticeable steps in involution occur during the latter part of the first week, and by the end of the second and third weeks the glands have returned approximately to their resting stage.

6S. Regulation of posture in the forelimb of Amblystoma punctatum. J. S. Nicholas (introduced by R. G. Harrison), Yale University.

The limb-bud of the right side of the embryo has been subjected to rotations of 90°, dorsoantorior or clockwise and dorsoposterior or counterclockwise, in order to study the factors which cause rotation in transplanted limbs. Regulatory recovery occurs, being practically complete in the normal location and partially so in abnormal locations. As a rule, the limb moves through the shorter arc in recovering its normal posture, that is, the recovery process is generally in the reverse direction from the imparted rotation. Exceptions to this rule, occurring in dorsoposterior operations, show that occasionally growth factors increase the imparted 90° rotation, causing the limb to attempt recovery through the greater arc or in the same direction as the imparted rotation.


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Irrespective of imparted rotation, girdle formation is in normal relation to the dorsoventral axis of the embryo, that is, it is never upside down, although it may be reversed in regard to the anteroposterior axis. The regulation of posture is primarily dependent upon the formation and size of the girdle. This is shown in heterotopic operations. The intrinsic musculature which grows back from the limb blastema to the girdle also apparently influences the recovery of the limb to its normal posture. The limb undergoes rotation as a whole. In contrast to this, the readjustment which occurs in the girdle is not by means of movements of the whole aggregate as shown by the position of portions of the pronephros which have been implanted with the limb-bud.

6 4. The developmental topography of the thymus, with particular reference to the changes at birth and in the neonatal period. (Lantern.) Gustave J. Noback, University of Minnesota.

The thymus in the late fetus and stillborn child has a typical form and quite constant relations. Its lateral surfaces are convex and bulge against the medial surfaces of the lungs which rarely extend at all on its anterior surface. The thymus very rarely extends at all on the anterior surface of the right ventricle of the heart.

The thymus in liveborn infants has a typical form and relations which are similar to those found in young children. It is elongated and molded so that its anterior, lateral, and posterior surfaces bear the impress of all the organs with which it is in contact. Its lateral surfaces usually show marked convexities which are occupied by the lungs which pass over the anterior surface of this organ. Unlike the fetal thymus, it extends on the right ventricle. The change from the broad or fetal type of thymus to the elongate and molded type found in the liveborn and in the young infant bears a direct relation to the establishment of respiration. The organ is compressed from side to side by the medial surfaces of the expanding lungs. It i's also compressed anteroposteriorly by the anterior borders of the lungs which advance medially and become much thickened early in the establishment of respiration.

65. The postnatal growth and developynent of the female reproductive tract in the albino rat. H. L. Osterud, University of Minnesota.

This study of the weights and microscopic structure of the ovaries, uterine tubes, uterus, and vagina of 125 rats (including thirty postpartum primiparae) shows that in adult virgin rats the tubes may attain a maximum growth of twentysix times their birth weight, the ovaries seventy-four times, the vagina 138 times, and the uterus 197 times. All four organs exhibit four-phase growth curves. The most rapid growth occurs first during the first three weeks (lactation period) and later shortly after the sixtieth day of age. The prepubertal growth increase comes distinctly earlier in the uterus and vagina than in the ovaries. After maturity the variability especially in the uterine weight is astonishing (from 0.055 to 0.494 per cent of the body weight). The maximum uterine weight in virgins far exceeds that in postpartum primiparae after completed uterine involution. The uteri of these postpartum primiparae, however, display the tendency to a similar great growth if kept from the males for sufficient time. The extreme cases strongly suggest a parallelism between this great uterine growth


76 AMERICAN ASSOCIATION OF ANATOMISTS

and ovarian activity, associated also with large hypophysis and perhaps thyroid. Failure of this great growth in some females is extremely dijERcult to account for except in cases of distinctly poor nutrition. Volumetric study of the ovaries offers no role in this uterine variability to the interstitial tissue. Definite correlation in the size of uterus and vagina is fairly evident, while the frequent apparent failure of the ovary to show similar correlation is probably due to its great cyclic fluctuation.

66. Developmental competition in its relationship to the sex ratio. George N. Papanicolaou, Cornell University Medical College.

The average sex ratio in a stock of 3472 guinea pigs is 106.54 when the individuals born in all litters are considered. On comparing the ratios from different-size litters great discrepancies are found. In litters of one the sex ratio is 112.58; in litters of two, 112.07; in litters of three, 97.95; in litters of four, 108.73, and in litters of five, 141.02. These variations may be explained on the following principles derived from a careful analysis of the developmental conditions in guinea pigs:

1. There is a competition between developing germ-cells and embryos in the ovary and the uterus.

2. In the competition males have some advantage over the females.

3. Competition is higher in the larger litters (by a litter is meant the number of codeveloping germ-cells and embryos).

4. In litters consisting of embryos of the same sex competition is higher than in mixed litters.

5. The competition is stronger among females than among males.

In agreement with these statements there is a higher percentage of complete elimination of large litters, consisting chiefly of females than of any other large litters. This elimination produces the high sex ratio for the litters of four and five. The originally large litters in which the subsequent elimination is partial result in births of one and two. Elimination being more severe on the female members causes the production of a higher sex ratio than occurs among individuals produced in litters of three. Litters of three have the lowest sex ratio and approach nearest an expected condition, having suffered little or no prenatal mortality. This explanation is supported by a study of more than 100 litters with early partial absorptions which gave the high sex ratio of 123.37.

67. A note on the relation of the auricle and external auditory canal to drum-membrane mechanics. A. G. Pohlman, Saint Louis University.

The writer presented certain comparative data at the last meeting of the Association on the problem of middle-ear mechanics. This evidence favored the 'string-telephone' theory of sound transmission and opposed the usualh' accepted theory of mass reactions. Practically all modern writers (^^rightson-Keith and Zimmermann excepted) agree that the drum membrane-ossicular chain route is the highly efficient one for so-called 'bone-transmitted' sound. Modern investigators of cochlear mechanics with few exceptions base the responses in the inner ear upon mass movements in the periotic fluid (functional relation of stapes basis to fenestra cochlease). It is essential that the reactions in the drum membrane to energies of optimum or minimum force be carefully studied. It appears that


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the dampening-out effect of the external auditory canal upon the sound pulses entering the external meatus through diffraction is more than compensated through the action of the auricle. An explanation of the Weber phenomenon or the Rinne-negative ear test does not appear satisfactory on the basis of the mass response conception. The increased efficiency of bone-transmitted sounds (mastoid and teeth) and the decreased efficiency of air-transmitted sound in pathological conditions of the middle ear is more readily explained by the 'stringtelephone' theory. This is also the case in the interpretation of instances of voluntary contraction of the M. tensor tympani and the dampening-out effect of heightened drum-membrane tension due to plus pressure in the external canal. A definite conception of drum-membrane mechanics is essential to the correct analysis of inner-ear responses.

68. The determination of the perce7Uage of the organic content of bone. H. E. Radasch, Jefferson Medical College.

The percentage of the organic substance in compact bone is given as 32 to 33 per cent. How that was determined is not apparent from the general literature. In order to determine the real percentage and to try to find out, if possible, the methods used by the early observers, experiments were made in various ways. After carefully preparing pieces of femur, tibia, and fibula, one set of pieces was weighed, then calcined, then weighed again. The loss indicated the amount of incinerable organic substance in compact bone. At twenty to sixty years the average per cent found was 40.75. In the adult cat this green weight per cent was found to be 38.32 per cent, while in the rabbit (two-thirds grown) the average was 38.90 per cent. By other methods the moisture, alcohol-soluble and ethersoluble substances were removed and the fixed organic content determined. The average amount of moisture at twenty to sixty years is 8.42 per cent and the ratio of fixed organic substance to the dried bone is only 34.92 per cent. The average amount of alcohol-soluble material is 8.46 per cent and the ratio of the fixed organic substance to the extracted bone is 32.36 per cent. The average amount of ether-soluble substance is 9.27 per cent ; the ratio of the fixed organic substance to the extractable bone averages 31.34 per cent. It seems, though, that the standard weight should be that of green bone, and if this be accepted, then the organic substance averages 40.75 per cent.

69. The distribution of the acid cells of the stomach. H. E. Radasch, Jefferson Medical College.

It is customary to state that the acid cells are found in the cardiac and fundal portions of the stomach, but there seems to be no definite statement as to the point or region at which they cease to exist. It was, therefore, determined to make a sort of survey of the stomach so as to see if it were possible to give any definite boundary to the acid-cell distribution and also to note any difference in distribution. For this purpose human and rabbit stomachs were fixed in toto and then, when dehydrating in 85 per cent alcohol, were cut. A strip J inch wide of the entire lesser curvature was first cut out, then one of the entire greater curvature and one of the ventral or dorsal surface, attempting to follow the long axis of the surface. These pieces (uncut) were then completely dehydrated, cleared in cedar oil and absolute alcohol (equal parts) and then pure cedar oil,


78 AMERICAN ASSOCIATION OF ANATOMISTS

and infiltrated in paraffin and then blocked without cutting into segments. After the paraffin had hardened the long strips were then cut into pieces If to 2 inches long (the width of the cut of a Spencer microtome) and sectioned. Such long strips may readily be cut into shorter strips by using a safety-razor blade. The stomach of the rabbit was run through whole, and if it would fit into the microtome was sectioned whole. If too large, the stomach block was cut into two pieces and sectioned in that condition. It was intended to study the stomachs in the stillborn also, but the material at hand at the time was unsatisfactory, but this will be taken up later.

70. The sublenticular portion of the internal capsule and the thalamic radiation to the temporal lobe. S. W. Ranson, Northwestern University Medical School. In dissections of the internal capsule its sublenticular portion is seen to be

composed of two strata. The upper stratum, immediately beneath the lentiform nucleus, is formed by the temporopontine tract. These fibers run directly lateralward into the temporal lobe. The lower stratum forms the roof of the inferior horn of the lateral ventricle and is composed for the most part of the temporothalamic fasciculus of Arnold. This bundle emerges from the thalamus near the external geniculate body, and forms a large strand directed forward in the roof of the inferior ventricular horn. A few at a time these fibers curve outward and then somewhat backward into the white matter of the temporal lobe. Another and smaller bundle of fibers can be traced from the stratum zonale in an arched course around the thalamus following the tail of the caudate nucleus. Passing through the sublenticular portion of the internal capsule, this fascicle flattens out in the roof of the inferior horn of the lateral ventricle under cover of the ependymal lining and can be traced forward to the anterior part of the temporal lobe. It lies on the ventricular surface of Arnold's bundle, and may be designated as the fasciculus thalamotemporalis arcuatus. It was seen by Probst ('05) in the brain of a monkey with an experimental lesion in the thalamus and by the same observer in the brains of microcephalic idiots.

71. The so-called hibernating gland. A. T. Rasmtjssen, University of Minnesota. For this structure many other names have been proposed : adipose gland, lipoid

gland, cholesterin gland, brown fat, organ of hibernation, hibernating mass. From about fifty papers available, its history consists of four periods. I. 1670 to 1817, during which it was generally regarded as part of the thymus. II. 1817 to 1863, during which it was generally recognized as distinct from the thj'mus, but still as a haemopoietic gland. III. Since 1863 it has generally been classed as a form of adipose tissue which serves as reserved food. IV. Its internal secretory character has been emphasized during the last ten years and recently ('20) as a factor in the etiology of deficiency diseases. From the reports of others on over forty species of animals and personal examination of numerous marmots (in which this structure is prominent), it is clear that histologically there is no similarity between it and the thymus. There is no evidence of any haemopoietic function. It is also different fron ordinary adipose tissue. The cells are rarely if ever unilocular. The nucleus is never flattened much. It never loses all its fat. During hibernation it supplies only about one-thirtieth of the material consumed, and hence, as far as bulk is concerned, is not an important


PROCEEDINGS 79

food reserve. While the cytoi)lasm of the cells is rich in small granules (in addition to the fat globules) and the organ surprisingly vascular, more careful cytological and physiological work must be done before its close relation to the suprarenal cortex, corpus luteum, or other ductless glands can be affirmed.

72. On the growth in weight of the human body and its various parts and organs in the fetal period and its expression by empirical formulae. Richard E. Scammon, University of Minnesota.

The growth in weight of the entire body in the fetal period presents, when plotted against total body length, a concave curve which may be expressed by the empirical formula, Y = (aX), when Y is the weight of the body in grams, X is the total body length in cm., and a and b are empirically determined constants. The absolute weights of the trunk, the extrernities, and the head also follow this course of growth and may be expressed by the same formula with modified constants. This form of growth is typical of almost all the organs of the body — certainly of the heart, kidneys, spleen, thymus, liver, stomach, pancreas, suprarenals, thyroid, eyeballs, brain, and spinal cord and, in all probability, of the lungs, testes, and uterus as well. The growth of these structures may be expressed by formulae of the same general form as that of body weight, although each appears as a minor variant of the common type. So far no evidence has been found of a grouping of these prenatal curves in categories comparable with the main classes of postnatal growth curves. Similar findings regarding the type of growth of the body and its pacts and organs are obtained when weight is plotted against age in fetal months.

73. The visual pathway and the paranasal sinuses. J. Paesons Schaeffer, Jefferson Medical College.

Recent clinical reports prompted me to undertake a more detailed study of the anatomic relationships between certain portions of the visual pathway and the paranasal sinuses than hitherto attempted in my work. An anatomic basis was sought for certain clinical manifestations. Some were cleared up, others remain obscure and require further study. It is well to recall that the optic nerve, the optic commissure, and the optic tract are formed in order by the same axones with cell bodies located in the retina and that, strictly speaking, one is dealing with a partially decussated brain tract, the fibers of which are medullatcd in the retro-ocular portion, but lack a neurolemma. Clinical findings arc in accord with this. The portions of the visual pathway that particularly concern us here are the so-called optic nerve and the optic commissure. The great variations in size, shape, number, and type, and the variations in symmetry and asymmetry of the paranasal sinuses preclude any constancy in the topographic relat ionships with the optic nerve and the optic commissure. The sphenoidal sinuses and the posterior ethmoidal cells are of first importance in this connection; however, the other sinuses may be a factor. Very, commonly the most intimate relationships exist.

Clinically it has been found that paranasal-sinus disease may give rise to ocular complications without external signs of orbital inflammation. Optic neuritis, neuroretinitis, phlebitis, etc., are encountered. More important, since it often occurs with but slight ophthalmoscopic change, is the occurrence of a central


80 AMERICAN ASSOCIATION OF ANATOMISTS

scotoma. The scotoma may be unilateral or bilateral, the latter despite the fact that but one side may be affected. The above conditions may rapidly advance to a state of blindness. It is surprising, however, how rapidly these conditions clear up, even the blindness, if the optic manifestations are early recognized and paranasal-sinus treatment properly and efficiently carried out. Want of such recognition and treatment early means permanent blindness from optic-nerve atrophy. Here an appreciation of the topographic anatomy of the optic pathway and the paranasal sinuses is of the greatest importance to those dealing with the eye and the nose clinically. Apropos in this connection is the report of a prominent ophthalmologist who in consultation found a patient totally and permanently blinded by an ill-advised curettage of the sphenoidal sinus, resulting in complete destruction of the optic chiasm. The underlying anatomy of the foregoing clinical findings will be discussed. Lantern.

74. Relation of nutrition to the oesirous cycle. Katharine J. Scott and Herbert

M. Evans, University of California.

In the study of the oestrous cycles of several hundred rats. Long and Evans reported a very considerable variation in cycle length, although in over 80 per cent of some 2000 observations, cycles of six days or less were found. These observers had had occasion to note the immediate impairment of ovarian function by increased cycle length whenever experimental animals were submitted to one or more days of undernutrition. Papanicolaou and Stockard have now established similar facts on the delay of the next oestrous of guinea-pigs due to undernutrition. The suggestion was near at hand and was, in fact, made by the lastmentioned workers that the considerable variation in the length of the oestrous cycles observed in our colony of rats might be referable to chance nutritive deficiencies unintentionally and inevitably introduced by feeding table scraps. We have submitted this question to test by placing some twenty-one animals upon our usual 'table-scrap' rations and twenty-one litter mates upon a diet employed by McCollum and certified to have yielded excellent growth and reproduction in this species over a number of yearrs. The McCollum diet consists of:

grams

Wheat (whole) 67.5

Casein 15.0

Whole-milk powder 10.0

Sodium chloride 1.0

Calcium carbonate 1.5

Butter fat 5.0

The animals at all times had access to an abundance of the food and of fresh water. At the beginning of the observations all of the animals were about 100 days old and the observations to date have extended over fifty days, opportunity being thus afforded for the observation of ten or more normal oestrous cycles. During this period the rats on the standard ration made an average gain in weight of 49 grams; those on the table-scrap diet, a gain of 42 grams. The average length of all cycles observed in animals on either ration was the same and was almost exactly five days. In the case of both diets about half the animals exhibited an uninterrupted series of oestrous cycles of six days or less in length and in each group of twenty-one animals three or four individuals showed more marked


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irregularity. Furthermore, two other larger groups of animals composed of ninety-five and seventy individuals, respectively, and of almost identical age but not litter mates were placed, the one on the standard ration, the other on table scraps, and a similar study of their oestrous cycles instituted. The data obtained w^ere concordant with the above. It cannot be considered, therefore that the irregularity which may be observed in the lengths of the oestrous cycle.s of young adult rats is always due to nutritive deficiency. We would not by this statement mean to deny the great importance of nutrition in maintainingthe oestrous rhythm. Studies of the effect on the oestrous rhythm of experimental undernutrition both qualitative and quantitative are under way.

75. The develoj)ment of the pharynx, and the histology of its adult derivatives, in turtles. Ralph F. Shaner, Harvard Medical School.

The pharynx of Chrysemys marginata develops five pouches. The last pouch, with the postbranchial body, arises from a common stem. There are six aortic arches and five nerve placodes. The second, third, and fourth pouches end secondarily in a common cervical sinus. The first three pouches have patent clefts. From the first pouch develops the auditory tube and the tympanicmastoid cavity. The second bears a dorsal knob of doubtful significance, which vanishes with it. The third and fourth develop persisting dorsal and ventral outgrowths. The fifth develops a transient dorsal (thymic) rudiment and then disappears; the postbranchial is then attached to the fourth pouch. The thyroid gland develops entirely from a median ventral diverticulum. The dorsal and ventral outgrowths of the third pouch separate off as a single independeni complex closely adherent to the carotid artery. The dorsal moiety becomes a large, lobulated, persistent, anterior thymus; the ventral one is transformed into an anterior parathyreoid, which is enclosed within the adult anterior thymus. The two outgrowths of the fourth pouch and the postbranchial body separate off as another independent complex, closely adherent to the systemic arch. The dorsal outgrowth persists as a variable posterior thymus ; the ventral as a large posterior parathyreoid. The postbranchial body develops chiefly on the left side ; it breaks up into numerous secretory vesicles. The three organs constitute the tiny aortic body, w^hich appears in the adult, attached to the aorta. The lobules of each thymus are divided into cortex and medulla, the latter containing thymic corpuscles. Each parathyreoid is made up of cords of epithelial cells, surrounded by vascular sinusoids. The postbranchial vesicles are of two t3'pes and contain a definite secretion.

76. The presence of a head cavity in a human embryo of 4 inm- Joseph L. Shellshear (introduced by G. L. Streeter).

The cavity is situated immediately posterior to the otic vesicle and mesial to the glossopharyngeal complex, and probably corresponds to Van Wijhe's 1st post-otic segment. Spindle-shaped cells arising from it are continuous with a clump of cells of a similar character situated mesial to the vagus complex. From this latter group of cells a migration is taking place which passes posterior to the vagus apparatus and is interpreted as the migration of the hypoglossal musculature.


82 AMERICAN ASSOCIATION OF ANATOMISTS

The cavity is regarded as homologous with the head cavities which give rise to the eye musculature. This type of cavity is peculiar to the median somatic or axial mesoderm and distinct from the coelom which is formed by a splitting of the lateral somatic mesoderm.

n. On the reaction of the living blood cells to dyes. M. E. Simpson (introduced by

H. M. Evans), University of California.

A drop of blood was caught on a cover and immediately brought in contact with a slide on which was a thin, dry film of dye. The method has been previously employed by Pappenheim, Rosin, and Bibergeil. Somewhat less than two hundred dye substances were carefully studied. The following generalizations may be made:

1. The dyes frequently collect in a definite set of granules, 'the segregation apparatus,' which can be differentiated from, 1) refractile granules (probably lipoid); 2) degeneration vacuoles; 3) specific granules, and, 4) mitochondria.

2. With some dyes a certain proportion of the granules enlarge rapidly, the vacuolar structures resulting therefrom having been described by Ferrata and termed 'plasmasomes.' But Arnold has used this term much more widely. Rosin and Bibergiel called them 'dye sphere formations.' They evidently correspond to what Renaut termed 'grains de segregation' in the connective-tissue cells. Dubrueil called them ' vacuoles a grains de segregation ; ' Hammar referred to them as 'purpurgranula,' whereas Evans and Scott, in their study of the reaction of connective tissues to vital stains, described the same .system of structures as 'the vacuolar apparatus.'

The segregation apparatus may be considered as a reaction on the part of the living cell for the purpose of segregating and isolating various foreign materials forced upon it. The ability to thus segregate dyes is common to all the white cells of the blood, but the extent of the segregation apparatus is characteristic for each cell type and may be used as a valuable point of distinction between the different kinds of mononuclear cells. The transitionals of Ehrlich or monocytes of Naegeli show the reaction to the greatest degree. Probably all dye groups contain members which would be handled in this way by the cell. The reaction is perhaps given most typically by certain of the oxazine, thiazine and azine dyes, but dyes showing the widest variation in chemical and physical properties appear to give this response.

78. The ingestion of melanin pigment granules by tissue culture cells grown from the embryo chick in Locke-Leins solution. David T. Smith (introduced by W. H. Lewis), Carnegie Laboratory of Embryology.

In cultures of chick embryos, melanin pigment granules from the retina of the chick, pig, dog, and man (newborn child) were taken in by clasmatocytes, fibroblasts, endothelial cells, white blood cells, and cells from lung, liver, kidney, intestine, and amnion by a process which appears quite different from that by which the amoeba ingest food. Peripheral nerve cells, striated muscle cells, and red blood cells did not ingest the granules. When a granule was free in the culture fluid it exhibited both Brownian movement and an actual progression from place to place; when attached to the cell wall it was motionless; after passing into the cytoplasm it displayed the jerky motion characteristic of pigment


PROCEEDINGS 83

granules in the true pigment cells, and finally, when a vacuole developed about a granule it reverted to Brownian motion. The granules were not taken into preformed vacuoles; but later, as they moved back and forth in the cytoplasm, a vacuole developed about each one or about each small clump of granules. The granules then exhibited Brownian movement, became swollen, disintegrated, and were reduced to debris.

Granules in the true pigment-producing cells are always individual and discrete bodies of about the same size and shape. The individuality and discreteness are common properties, but size and shape vary in cells of different origins. The granules in normal pigmented cells are never found clumped into vacuoles or broken up into debris. It can therefore be determined by the appearance of the granules whether they have been produced or ingested by the cell. This fact should help us to settle the old question of pigment-producing versus pigment-carrying cells.

79. Some modifications induced by parabiotic union of the hypophysectomized to the normal tadpole. Philip E. Smith, University of California. It appears of interest to determine whether the disturbances resulting from early hypophysectomy in the tadpole may be modified by a vascular interchange between the normal and the pituitaryless individuals, and to observe any compensatory alterations that may occur in the normal member of the pair. Hypophysectomized individuals were united at an early stage (5 mm.) to normal larvae. Both members of four pairs completed metamorphosis, and several pairs reached a nearly maximal larval size. In every case the pigmentary and endocrine disturbances typical of hypophysectomy were modified. Albinism, though evident, was only partial. Examination of the living animal and of cutaneous whole mounts revealed the fact that the xantholeucophores were not as broadly expanded, the epidermal melanophores not as scanty in number, as poor in melanin content, nor as contracted as in the typical hypophysis-free tadpole. The thyroids of the albinous member, instead of being diminutive, as would otherwise have been the case, were nearly normal in size, while those of the normal mate exhibited a slight hypertrophy. The adrenal cortex while reduced did not appear to suffer the same great reduction as that which normally occurs in the typical Albino. The vascular interchange did not modify the greatly reduced and atypical neural lobe of the Albino, nor did it appear to have caused an hypertrophy of the hypophysis of the normal member of the pair.

80. Upon the essentiality of the buccal component of the hypophysis for the continuance of life. Philip E. Smith, University of California. The above-mentioned parabiotic pairs were united in several ways, one of which, a union of the corresponding sides of the tail-stalks, is of especial interest here. Two such pairs completed metamorphosis. It is obvious that the attachments would be severed by metamorphosis. One pair completely separated; in the other an atrophic connecting strand persisted. Both members of each pair displayed the usual activity up to three or four days prior to the completion of metamorphosis. The hypophysectomized members then became more sluggish and exhibited a slowed respiration. One of them died just after the separation, the other just before the separation would have taken place. The separation


84 AMERICAN ASSOCIATION OF ANATOMISTS

in no way embarrassed the normal member of either pair. These members displayed their usual activity. In two other pairs joined by their heads, metamorphosis did not result in the death of the hypophysectomized specimen, probable due to the persistence of the vascular interchange.

Mammalian experimentation appears to have established the fact that the neural lobe is not essential to life. The essentiality of the anterior lobe has been questioned, death from its removal being referred by some to injury of the neighboring structures, not to hypophysial deficiency. In this experiment there was no injury to the brain or other neighboring structures, yet the animals promptly died when, in the adult stage, they were deprived of the secretion of the buccal hypophysis. The functional similarity which experimental work has shown to exist between the parts of the amphibian and mammalian hypophyses makes it highly probable that this component is essential for life in the mammal as well.

81. Does the administration of anterior lobe to the tadpole produce an effect similar to that obtained from thyroid feeding? Philip E. Smith and Garnett Cheney, University of California.

In a recent paper Hoskins and Hoskins have advanced evidence showing that the administration of a commercial anterior-lobe preparation to the normal and thyroidless tadpole gives an effect similar to that which is characteristic for thyroid administration, i.e., causes metamorphosis. This evidence would indicate that the anterior lobe and the thyroid are in this respect functionally similar, and so supports the hypothesis that they may function vicariously. These results are at variance with those obtained by fresh anterior-lobe feeding. We have found that the feeding of the particular commercial preparation used by the Hoskinses gives the results obtained by them. Two other commercial preparations, the dried gland prepared in this laboratory and the fresh gland, failed to give similar effects. Analysis by Doctor Kendall showed that this commercial preparation contained iodine greatly in excess of the norm- 1 amount.

Iodine as KI was added to the dried gland prepared in this laboratory in a sufficient amount to give an iodine content identical with this commercial product. Tadpoles receiving this substance did not exhibit a decisive acceleration of metamorphosis. In another case iodine as thyroxin iodine was added in identical amounts. Normal and thyroidless tadpoles receiving this substance paralleled in development the animals fed with the commercial preparation in question. The evidence indicates that a similarity of response is not evoked by thyroid and hypophysial administration. The anterior-lobe preparation used by the Hoskinses contained an unusual amount of iodine and displayed an altogether unique activity.

82. On the presence of longitudinal collector nerves in the tail of the skate and dogfish. Carl Casket Speidel, University of Virginia.

In the tail of the skate there are present four longitudinal collecting nerve trunks. These extend throughout the tail, but are not present in the body proper. They are located two on each side of the vertebral column, close to the bodies of the vertebrae. The dorsal collector on each side is opposite the junction of the neural arch and centrum of each vertebra. The ventral collector on each side is opposite the junction of the haemal arch and centrum of each vertebra.


PROCEEDINGS 85

These collectors are fed regularly by the spinal nerves according to thefollowing system: the ventral root from the spinal cord unites with the dorsal root emerging from the succeeding intervertebral foramen. From this junction emerge two rami, one of which connects with the dorsal collector, the other with the ventral collector. Branches to the muscles and electric organs are given off from these rami. No branches were found from the collectors to the electric organs. Small branches from the collecting trunks to the blood-vessels led to the supposition that they might represent a sort of primitive sympathetic system, a forerunner of the sympathetic system of higher vertebrates. Osmic-acid preparations, however, showed no non-medullated fibers. All the nerve fibers were meduUated. Similar collecting nerve trunks have been found in the tail of the dogfish and shark, although the connections with the spinal nerves w^ere somewhat different.

83. Comparative study of large irregular cells in the spinal cord of other fishes homologous to the giant glandular cells in the spinal cord of the skates. Carl Caskey Speidel, University of Virginia.

In the caudal portion of the spinal cord of the skate there are present large irregular cells of glandular character. Cells homologous to these have been found in more than thirty genera of fishes. These include both fresh- and saltwater forms, and represent the elasmobranch, teleost, and ganoid fishes. In three genera of fishes the cells were not found. In most of the forms the cells are neither so conspicuous nor so active as in the skate. Granular secretion is usually scanty or lacking. A form of special interest is the summer flounder in which the cells are extraordinarily large and numerous. This unusual type of cell, then, may be said to occur in the great majority of fishes, reaching its greatest degree of development in the skate and flounder. A doubtful homologous cell has been found in the ventral nerve cord of the lobster, but not in the horseshoe crab. In none of the vertebrates higher than fishes have the cells been found.

84. Experiments on the development of the cranial ganglion and the lateral-line sense organs in Amblystoma. L. S. Stone (introduced by R. G. Harrison), Yale University.

These experiments involve the removal of placodes and neural-crest cells. In normal development the crest cells migrate ventrally over the mesoderm of the visceral arches, around which they w^rap themselves, and finally become situated on their median surfaces, where they form the visceral skeleton. The appearance of a few mesodermal yolk granules among the crest-cell aggregations gives one the impression that there may be a slight mesodermal contribution to the visceral skeleton. When the crest cells are removed, a few cases show an incomplete formation of the visceral skeleton, but no defects in'the ganglionic components are observed due either to the fact that they may take no part in the formation of the ganglia or to the difficulty in eliminating the crest cells on account of their persistent ability to regenerate. All groups of lateral-line organs have separate primordia, except possibly the maxillary group, which may be a branch of the ventral hyomandibular. When sheets of ectoderm, taken anterior and posterior to the position of the ear, are removed at the closure of the neural folds, the body lines, occipital and supra-orbital primordia and their corresponding


86 AMERICAN ASSOCIATION OF ANATOMISTS

lateral line ganglia are absent. Removal of the epibranchial placodes of VII, IX, and X produces small ganglia apparently lacking visceral sensory and cutaneous components. Placodes of vagus and facial lateral-line ganglia interchanged produce in their new positions irregular groups of many sense organs innervated by fibers from lateral-line ganglia in the transplanted region.

85. A icell-preserved human embryo of the presomite period. George L. Streeter, Department of Embryology, Carnegie Institute of Washington.

Lantern slides will be shown of a young human embryo which was found at autopsy by Dr. H. G. Weiskotten, of Syracuse University. The patient, twenty years old, having skipped one menstrual period, died after an extensive pelvic retroperitoneal hemorrhage, presumably originating from an attempt to induce an abortion. The embedded ovum was found in the fundus of the uterus, and, together with the adjacent portion of the uterine wall, was placed in 10 per cent formalin seven and one-quarter hours after the death of the patient. Due to the handling of the specimen during its removal, the ovum and its decidual capsule were partially loosened from the implantation site and apparently flattened, but otherwise the specimen appears to be normal and in an excellent state of preservation. The external diameters of the decidual capsule are 16 X 12 X 5.3 mm. The diameters of the chorionic cavity are 9 X 7.3 X 2 mm. The embryo, i.e., the yolk'-sac and amniotic vesicle combined, measures 2.2 X 2.1 X 1.2 mm. The greatest width of the embryonic shield is slightly less than 1 mm. On account of its being bent upon itself, the length cannot as yet be accurately stated. The general form of the embryo and the character of the chorionic villi will be shown in the slides.

86. The order, lime, and rate of ossification of the skeleton. II. Mammals. R. M. Strong, Loyola University School of Medicine.

The white rat has been the type used for most of the mammalian portion of this work to date. The results contain too manj' details for the space allowed in an abstract. Some of them are mentioned here: A series of features of the skull, girdles, and long bones have been studied. Stages from the first appearance of ossification to senility (730 days) have been compared.

As in the bird, beginning ossification occurs in several bones at about the same time. The first ossification stages occur fully a week later in rat embryos than in the chick. At seventeen days and fifty-five minutes after insemination, ossification was found well started in the mandible, clavicles, and in the second to eleventh ribs. It had also begun in the maxilla, palatine, premaxilla, orbital portion of the frontal, humerus, radius, and ulna. The scapula showed ossification at seventeen days and eight and one-fourth hours. This had extended to a large portion of the spine several hours later. An ossification center was found in the coracoid process at three days after birth, and fusion with the scapula early in the fourth month. Ossification centers appear in the ilium, femur, tibia, and fibula at eighteen days nine and a half hours. They appear in the ischium and pubis at nineteen days eight and three-fourths hours. In the same embryo, the deltoid crest is well started, and it resembles the adult form a day later. Except for changes in size and general form, the rat skeleton is essentially mature at the end of the first year. Only slight stages take place after the third month.


PROCEEDINGS 87

87. Situs hivcrsns in dxmhlc (rout. F. H. Swett, Yale University. Examination has been made of the situs viscerum in fifteen douhie trout embryos and the findings resolve themselves into the following classes : In nine cases the situs viscerum of both components is normal; in one, that of A (the right twin) is reversed; in two, B (the left twin) is reversed, and in three B is normal, A of indeterminate situs. One of the cases which shows situs inversus in component B is of the auto site-parasite type and it is the parasite which is reversed. A definite correlation between the amount of external or internal doubling and the occurrence of situs inversus cannot be demonstrated.

88. The relation of the pars intermedia of the hypophysis and the pineal gland to pigmentation changes in anuran larvae. W. W. Swingle (introduced by R. G. Harrison), Yale University.

Homoplastic and heteroplastic transplants of the pars intermedia of the hypophysis from adult frogs of the species Rana catesbeiana, Rana climitans, and Rana pipiens were made into bullfrog tadpoles of various ages and sizes. The effect upon growth and metamorphosis of the animals w^as negative, but pigmentation changes following transplantation of the tissue were very marked. Within twenty-four hours after engrafting the pars intermedia either intraperitoneally or into the abdominal lymph spaces the larvae became deeply pigmented, changing color from a light yellow to almost black. The color change is due to marked expansion of the melanophores of the skin, though the deeper-lying pigment cells of the tadpole also expand. The increased pigmentation lasts as long as the engrafted pituitary tissue remains functional and is not resorbed. Following resorption of the graft, the animals resume normal coloration. The environment apparently plays no part in the color change following transplantation of the pars intermedia; the change is due to the stimulating effect of the hormone either directly upon the melanophores or else indirectlj- through the intermediation of the nervous sj^stem.

There is a possible interrelationship of the pars intermedia to the pineal gland in the production of pigmentation changes in anuran larvae. Darklj' pigmented tadpoles engrafted with the pineal gland of reptiles (Chelonia) change color within an hour following transplantation; the expanded melanophores contract and the animals become lightly pigmented. This condition persists for several hours; then slowlj^ normal pigmentation is resumed. Similar changes follow introduction of desiccated mammalian pineal tissue into body cavity.

89. Mammalian pubic metamorphosis. (Stereo-lantern.) T. Wixgate Todd, Western Reserve University.

In comparing skeletal growth and metamorphosis of man with similar features in other mammals, it is necessary to utilize some standard subdivision of the total life period. In our present work the best subdivision is the following:

1st life period. Terminates in complete union of the acetabular elements.

2nd life period. Terminates in complete union of epiphj^ses with long bones.

3rd life period. Terminates in complete union of epiphyses with vertebral centra.

4th life period. Between the termination of the 3rd and the commencement of the 5th period.


88 AMEKICAN ASSOCIATION 'OF ANATOMISTS

5th life period. Commences with lipping of the glenoid margins of the scapulae.

6th life period. Commencement of senile (quasipathological) erosions and osteophytic growths at joints, and senile textures of bones.

These features, unlike eruption of teeth, closure of cranial sutures and others not here mentioned, present definite relationships to the total life period. Compared with each other they do not represent even approximately equal time relationships. Judged by these standards, it is possible to observe the delay in commencement and still more in completion of pubic metamorphosis as evidenced by higher mammals and by man. At the same time the gradual evolution of the features of this metamorphosis can be studied. Its progressive features are exemplified in members of some orders, other members of which show retrograde conditions. Man falls into the latter group.

90. The skull as a closed box. Lewis H. Weed and Walter Hughson, Johns

Hopkins Medical School.

The experiments of Weed and McKibben, reported two years ago, demonstrated that the pressure of the cerebrospinal fluid may be markedly lowered and frequently reduced to negative values by appropriate intravenous injections of strongly hypertonic solutions. These findings suggested that the cerebrospinal axis was enclosed within a rigid system, but absolute proof of the 'closed-box' character of the coverings was lacking. Experiments recently performed indicate that if the bony calvarium on one side be removed without opening the dura mater and if the pressure of the cerebrospinal fluid be taken, repeated intravenous injections of strongly hypertonic solutions fail to reduce the pressure to below zero. Likewise, if the bony calvarium on one side be opened and then temporarily sealed, appropriate intravenous injections of the hypertonic solutions will reduce the pressure of the cerebrospinal fluid to negative readings. Under these circumstances, opening the cranial cavity by removal of the sealing device will cause the pressure of the fluid to become immediately positive, the level of the positive pressure being determined by the hydrostatic height of the brain above the needle. These experiments can be explained only upon the hypothesis that within minimal limits the cranium and vertebral canal form a closed system within which lies the central nervous system.

DEMONSTRATIONS

/. The motor cortex of the brain of the sheep. Charles Bagley, Jr., Johns Hopkins University.

2. The development of connective tissue. George A. Baitsell, Yale University.

3. a — De-electrification of paraffin ribbon, b — Differential bone stains for macroscopic transparent preparations. O. V. Batson, University of Wisconsin.

4. Injection of blood vessels of the lung of the chick during third day of incubation to show the origin of pulmonary veins. Charles E. Buell, Jr. (introduced by Florence R. Sabin), Johns Hopkins Medical School.

5. Plates of a radiographic atlas of anatomy. H. S. Burr, Yale University, School of Medicine.


PROCEEDINGS 89

6. Model of the principal fiber tracts of the central nervous STjstem. J. L. JackowiTZ (introduced by H. S. Burr), Yale University, School of Medicine.

7. Microscopic slides, drawings and graphs illustrating bone, muscle and joint origin in the thigh of the pig (Sus scrofa). Eben J. Carey, Marquette School of Medicine.

8. Sections illustrating the effect of stress and strain upon the healing of bone injuries. Eliot R. Clark and Ralph R. Wilsox, University of Missouri.

9. Digestion of different proteins by the mesenchijme and its derivatives in the tadpole. Vera Danchakoff, Columbia University.

10. Various techniques used in scientiHc illustration. Erwin F. Faber, University of Pennsylvania.

11. Preparations showing the absorption and assimilation of fat. Simon H. Gage, Cornell University.

12. A case of hermaphroditism in the pig. Harley N. Gould, Lake Forest College.

13. a — Thyreo-parathyroidectomised and parathyroidectomised albino rats, b — Effects of removal of the thyroid apparatus on bone growth of albino rate, c — Malformation of the femur and humerus accompanying abdominal tumor in a female albino rat. Frederick S. Ham.mett, The Wistar Institute.

14. Injected pig embryos cleared by the Spalteholz method to show the development of the innominate artery. Chester H. Heuser, Johns Hopkins Medical School.

15. Demonstration of the value of x-ray in anatomical teaching and research. Ebex C. Hill, Johns Hopkins Medical School.

16. Regenerative processes in the spinal cord of frog larvae severed previous to metamorphosis. Davenport Hooker, University of Pittsburgh.

17. Section cutting of the dental tissues by means of the ether-vaporizing microtome. A. Hopewell-Smith, University of Pennsylvania.

18. Stereoscopic photographs of human embryos. N. Williams Ingalls, School of Medicine, Western Reserve University.

19. Sections of chick embrijos showing ganglia of the sijmpathetic trunks derived from cells which advanced peripherally along the fibers of the ventral nerve-roots in segments in which the spinal ganglia and dorsal nerve-roots are absent. Albert KuNTz, St. Louis University.

20. A method for preserving cadavers in the dissecting-room. Frederic P. Lord, Dartmouth Medical School.

21. Histological preparations showing various stages in lactation and subsequent involution of the mammary gland in the albino rat. L. I\L A. ]\L\eder (introduced by C. M. Jackson), University of Minnesota.

22. Microscopic sections showing functional variations in normal human mammary glands. Joseph McFarland, University of Pennsylvania.

23. Cleared preparations illustrating the involution of the mammary gland in the female albino rat. Frank J. Myers (introduced by J. A. Myers), University of Minnesota.

24. a — A graph illustrating simple formulae for correlating crown-heel and crownrump length in fetal life, b— Material illustrating the developmental topography of the thymus with particular reference to the changes at birth and in the neonatal period. Gtjstave J. Noback, University of Minnesota.

25. a — Wax reconstruction of the nuclear masses in the brain stem of a sheep. James W. Papez, Cornell University.


90 AMERICAN ASSOCIATION OF ANATOMISTS

^^_ 5 — ]Yax reconstruction of the olivary nuclei of the sheep, rabbit, dog and bear.

James W. Papez. Cornell University.

The inferior olivary nucleus of the rabbit, sheep, dog and bear is divisible into the dorsal, ventral and intermediate olivary nuclei and the olivary sac. The dorsal nucleus is an oval plate that lies dorsal to the sac and is secondarily separated from its dorsal lip. The ventral nucleus is a thick oval plate that extends the entire length and with the intermediate nucleus forms the caudal end of the olivary complex. Orally its medial margin is secondarily separated from the ventral lip of the sac. The intermediate nucleus is formed of three parts; the paramedian plate at the caudal end of the complex united with the ventral nucleus, the intermediate plate extending laterally to the caudal end of the ventral lip of the sac, and the olivary bridge extending from the paramedian plate laterally to join the narrow caudal ends of the dorsal nucleus and sac. The olivary sac is a simple oval sac, compressed dorsoventrally with its opening towards the mid line. The sac is situated in the oral portion of the olivary complex where it intervenes between the dorsal and ventral nuclei. The hypoglossus nerve perforates the dorsal nucleus and lateral end of bridge and in the rabbit also the sac. The larger oral portion of the olivary nucleus appears to have been rotated laterally in the expanded portion of the bulb while the caudal portion has retained a more fixed position oral to the decussation of the cerebrospinal tracts.

27. Materials in a case of multiple atresia of the jejunum of a young child suggesting etiological factors. C. W. M. Poynter, University of Nebraska Medical College.

28. a — Field graphs, curves and charts illustrating the growth of the various external dimensions of the human body in the fetal period. L. A. Calkins (introduced by R. E. Scammon), University of Minnesota.

29. b — Material illustrating the growth of the brain and its parts and of the spinal cord in the fetal period of man. H. L. Dunn (introduced by R. E. Scammon), University of Minnesota.

30. c — Graphs and charts illustrating the growth in weight of the body as a whole and its various parts and organs in the fetal period of man. R. E. Scammon, University of Minnesota.

31. Histological preparations of experimentally doubly-ligated blood vessels, showing the fate of the contained blood and the behavior of the intima. J. Parsons Schaeffer and H. E. Radasch, Jefferson Medical College.

32. A series of graphs illustrating the changes in the form of the thorax at birth and in the neonatal period. Richard E. Scammon amd William E. Rucker, University of Minnesota.

'These graphs are based upon measurements of the chest in fetuses, full-term children and a series of infants less than two weeks old. The horizontal chest circumference is greatly increased with the first inspiration, but in the course of the first 24 hours enters a period of decrease which continues for three or four days. Following this is a second phase of circumference gain which continues throughout the remainder of the period of observation. The diameters of the thorax undergo changes similar to those of the chest circumference. The thoracic index stands below 90 in the latter part of the fetal period, but it rises to an average of about 106 with the establishment of respiration, and then drops


PROCEEDINGS 91

to about 102 in the first 24 hours. Thereafter it declines irregularly to about 100.5 in the middle of the second postnatal week.

35. Cinematotnicography of serial sections. W. F. Schreiber, Stacy R. Guild, and L. G. Herrmann, Anatomical Laboratory, University of Michigan.

34. Histological preparations showing the effects of inanition upon the development

and structure of the testis in the albino rat. David M. Siperstein (introduced

by C. M. Jackson), University of Minnesota. 85. Model illustrating the effect on the growth of the sacrum following early removal

of the posterior limb-bud in chick embryos. R. G. Spurling (introduced by E.

R. Clark), University of Missouri.

36. Charts showing the weight of the ovaries during the reproductive cycle in albino rats, a — During gestation; b — During normal la<:tation; c — In females deprived of their litter at birth. J. M. Stotsenburg, The Wistar Institute.

37. Unique case of ectopic pregnancy. G. L. Streeter, Carnegie Laboratory of Embryology.

A chorionic sac containing a normal human embryo of about eight weeks development which was obtained by operation from the subcutaneous tissue superficial to the rectus mijscle midway between the umbilicus and the pubis.

38. Cleared embryos and postembryonic stages. R. M. Strong, Loyola University School of Medicine.

39. Free costal bars of the epistropheus of an adult man. Paul K. Webb (introduced by R. J. Terry), Washington University School of [Medicine.

This rare variation is interpreted as further evidence of the tendency to reduction and special modification of the vertebrae at the cranial end of the column.

40. Anomalous right subclavian artery in man. William A. Hudson (introduced by R. J. Terry), Washington University School of Medicine.

The relation of this variant to the oesophagus and the presence of an 'aneurysmal' swelling at its origin have been regarded as possibly causing dysphagia in the subject; it is suggested that the pressure of the anomalous vessel upon the thoracic duct may be a factor in the incidence of slow starvation recorded in connection with this variation. Absence of a right recurrent nerve and origin of the inferior laryngeal directly from the vagus is of practical interest in the operations for goitre.

41. Chondrocranium of Caluromys philander. Wax plate model from a 17 mm. embryo. Walcott Denison and R. J. Terry, Washington University School of ^ledicine.

Of special interest are: the shallow pituitary fossa and rudimentary dorsum sellae; absence of a true optic foramen; high degree of independence of the nasal capsules; presence of paired vomers; an unpaired nasal ossicle (os carunculae).

42. Vitally stained polymorphonuclear leucocytes in the placenta. George B. WiSLOCKi, Johns Hopkins Medical School.


CONSTITUTION Article 1

Section 1. The name of the Society shall be "The American Association of Anatomists."

Sec. 2. The purpose of the Association shall be the advancement of anatomical science.

Article 11

Section 1. The officers of the Association shall consist of a President, a Vice-President, and a Secretary, who shall also act as Treasurer. The President and the Vice-President shall be elected for two years, the Secretary for four years. In case of absence of the President and Vice-President, the senior member of the Executive Committee shall preside. The election of all the officers shall be by ballot at the annual meeting of the Association and their official term shall commence with the close of the annual meeting.

Sec. 2. At the annual meeting next preceding an election, the President shall name a nominating committee of three members. This committee shall make its nominations to the Secretary not less than two months before the annual meeting at which the election is to take place. It shall be the duty of the Secretary to mail the list to all members of the Association at least one month before the annual meeting. Additional names for any office may be made in writing to the Secretary by anv five members at any time previous to balloting.

Article 111

The management of the affairs of the Association shall be delegated to an Executive Committee, consisting of eleven members, including the officers. Two members of the Executive Committee shall be elected annually and, so far as possible, election of members of the Executive Committee shall be in proportion to the geographical distribution of members. Five shall constitute a quorum of the Executive Committee.

Article IV

The Association shall meet at least annually, the time and place to be determined by the Executive Committee. The annual meeting for the election of officers shall be the meeting of convocation week, or in case this is not held, the first meeting after the new year.

Article V

Section 1. Candidates for membership must be persons engaged in the investigation of anatomical or cognate sciences, and shall be proposed in writing to the Executive Committee by two members, who shall accompany the recom 93


94 AMERICAN ASSOCIATION OF ANATOMISTS

mendation by a list of the candidate's publications, together with references. Their election by the Executive Committee, to be effective, shall be ratified by the Association in open meeting.

Sec. 2. Honorary members may be elected from those who have distinguished themselves in anatomical research. Nominations by the Executive Committee must be unanimous and their proposal with a reason for recommendations shall be presented to the Association at an annual meeting, a three-fourths vote of members present being necessary for an election.

Article VI

The annual dues shall be seven dollars. A member in arrears for dues for two years shall be dropped by the Secretary at the next meeting of the Association, but may be reinstated at the discretion of the Executive Committee on payment of arrears.

Article Vll

Section 1. Twenty members shall constitute a quorum for the transaction of business.

Sec. 2. Any change in the constitution of the Association must be presented in writing at one annual meeting in order to receive consideration and be acted upon at the next annual meeting; due notice of the proposed change to be sent to each member at least one month in advance of the meeting at which such action is to be taken.

Sec. S. The ruling of the Chairman shall be in accordance with "Robert's Rules of Order."

The orders adopted by this Association, which read as follows, have not been altered:

Newly elected members must qualify by payment of dues for one year within thirty days after election.

The maximum limit of time for the reading of papers shall be fifteen niinutes.

The Secretary and Treasurer shall be allowed his tra\eling expenses and the sum of SIO toward the paj-ment of his hotel bill, at each session of the Association.

That the Association discontinue the separate publication of its proceedings and that the Anatomical Record be sent to each member of the Association, on payment of the Annual Dues, this journal to publish the proceedings of the Association.


AMERICAN ASSOCIATION OF ANATOMISTS

OFFICERS AND LIST OF MEMBERS

Officers

President Charles F. W. McClure

Vice-President T. Wingate Todd

Secretary-Treasurer Charles R. Stockard

Executive Committee

For term expiring 1921 George S. Huntington, Harvey E. Jordan

For term expiring 1922 Charles W, M. Poynter, Herbert M. Evans

For term expiring 1923 G. Carl Huber, Lewis H. Weed

For term expiring 1924 S. Walter Ranson, Robert J. Terry

Delegate to the Council of A.A.A.S. Simon Henry Gage

Representative to the National Research Council Charles R. Stockard

Committee on Nominations for 1921 R. G. Harrison, Chairman, H, H. Donaldson and G. Carl Huber

Honorary Members

S. Ram6n y Cajal Madrid, Spain

John Cleland Cretvkerne, Somerset, England

Camillo Golgi Pavia, Italy

Oscar Hertwig Berlin, Germany

A. Nicolas Paris, France

L, Ranvier Paris, France

Wilhelm Roux Halle, Germany

Members

Abbott, Maude E., A.B., CM., M.D., Curator of the Medical Museum, McGill University, Montreal, Canada.

Addison, William Henry Fitzgerald, B.A., M.D., Professor of Normal Histology and Embryology, School of Medicine, University of Pennsylvania, Philadelphia, Pa.

Adelmann, Howard B., B.A., Assistant in Histology and Embryology, Cornell University, Stimson Hall, Ithaca, N. Y. 95


96 AMEEICAN ASSOCIATION OF ANATOMISTS

Alford, Leland Barton, A.B., M.D., Associate in Clinical Neurology, Washington University School of Medicine, Hiunboldt Building, St. Louis, Mo.

Allen, Bennet Mills, Ph.D., Professor of Zoology, University of Kansas, 1653 Indiana Street, Lawrence, Kans.

Allen, Edgar, Ph.B., A.M., Instructor in Anatomy, Washington University School of Medicine, 4555 McKinleij Avenue, St. Louis, Mo.

Allen, Ezra, A.M., Ph.D., Professor of Biology, Ursinus College, Collegeville, Pa.

Allen, William F., A.M., Ph.D., Professor of Anatomy, University of Oregon Medical School, Portland, Oregon.

Allis, Edward Phelps, Jr., M.D., LL.D., Palais de Carnoles, Menton (A.M.) France.

Appleby, J. I., A.B., M.D., St. Vincent's Hospital, Toledo, Ohio.

Arai, Hayato, M.D., Chief Gynecologist, Sapporo Hospital, Sapporo, Japan.

Arey, Leslie B., Ph.D., Professor of Microscopic Anatomy, Northwestern University Medical School, 2421 Dearborn Street, Chicago, III.

Atterbury, Ruth Rand, A.M., I40 Broadway, New York City.

Atwell, Wayne Jason, A.M., Ph.D., Professor of Anatomy, University of Buffalo Medical College, 24 High St., Buffalo, N. Y.

Badertscher, J.\cob a., Ph.M., Ph.D., Associate Professor of Anatomy, Indiana University School of Medicine, 312 South Fcss Avenue, Bloomington, Ind.

Bagley, Charles, Jr., M.D., Major M. C, 5 West Chase Street, Baltimore, Md.

Bailey, Percival, M.D., Ph.D., Assistant in Surgery, Peter Bent Brigham Hospital, 721 Huntington Ave., Boston, Mass.

Baitsell, George Alfred, M.A., Ph.D., Assistant Professor of Biology, Yale University, Osborne Zoological Laboratory, New Haven, Conn.

Baker, Wilmer, M.D., Assistant Professor of Anatomy, School of Medicine, Tulane University, New Orleans. La.

Baldwin, Wesley Manning, A.M., M.D., Professor of Anatomy, Albany Medical College, Albany, N . Y .

Bardeen, Charles Russell, A.B., M.D. (Ex. Com. '06-09, Vice-President '18- '20) Professor of Anatomy and Dean of Medical School, University of Wisconsin, Science Hall, Madison, Wis.

Bartelmez, George W., Ph.D., Associate Professor of Anatomy, University of Chicago, Chicago, III.

Bartsch, Paul, M.S., Ph.D., Professor of Zoology, George Washington University, Curator Marine Invertebrates, U. S. National Museum, Washington, B.C.

Bates, George Andrew, M.S., D.M.D., Professor of Histology and Embryology, Tufts College Medical School, 416 Huntington Avenue, Boston, Mass.

Batson, O. v., A.m., M.D., Instructor in Anatomy, University of Wisconsin, 810 N. Bearly St., Madison, Wis.

Bau-mgartner, Edwin A., Ph.D. M.'D.,Halstead Hospital, Halstead, Kansas.

Bau-mgartner, William J., A.M., Associate Professor of Zoology, University of Kansas, Lawrence, Kans.

Bayon, Henry, B.A., M.D. , Professor of Applied Anatomy, Tulane University, 2212 Napoleon Avenue, New Orleans, La.

Bean, Robert Bennett, B.S., M.D., Professor of Anatomy, University of Virginia, Preston Heights, University, Va.


PROCEEDINGS 97

Beck, Claude S., A.B., Medical Student, Johns Hopkins Medical School, Baltimore, Maryland.

Begg, Alexander S., M.D., Instructor in Anatomy, Harvard Medical School, Boston, Mass.

Bensley, Robert Russell. A. B., M.B., Sc.D. (Second Vice-Pres. '06- '07, Ex. Com. '08-'12, President '18-'20), Professor of Anatomy, University of Chicago, Chicago, III.

Bevan, Arthur Dean, M.D. (Ex. Com. '96-98), Professor of Surgery, University of Chicago, 122 South Michigan Blvd., Chicago, III.

Bigelow, Robert P., Ph.D., Associate Professor of Zoology and Parasitology, Massachusetts Institute of Technology, Cambridge 39, Mass.

Black, Davidson, B.A., M.B., Professor of Neurology and Embryology, Peking Union Medical College, Peking, China.

Blair, Vilrat Papin, A.iNI., M.D., Associate in Clinical Surgery, Washington University School of ^Medicine, Metropolitan Building, St. Louis, Mo.

Blaisdell, Frank Ellsworth, Sr., M.D., Associate Professor of Surgery, Medical Department of Stanford University, Sacramento and Webster Sts., San Francisco, Calif.

Blake, J. A., A.B., Ph.B., M.A., M.D., 116 East 53rd Street, Neiv ForA- City.

Bonney, Charles W., A.B., M.D., Associate in Anatomy, Jefferson Medical College, 1117 Spruce Street, Philadelphia, Pa.

BoYDEN, Edward Allen, A.M., Ph.D., Assistant Professor of Comparative Anatomy, Harvard Medical School, Boston, Mass.

Bremer, John Lewis, A.B., M.D., (Ex. Com. '15-'18), Associate Professor of Histology, Harvard Medical School, Boston, Mass.

Broadnax, John W., Ph.G., M.D., Associate Professor of Anatomy, Medical College of Virginia, Richmond, Va.

Brookover, Charles, M.S., Ph.D., Professor of Anatomy, Histology and Embryology, University of Louisville, Medical Department, 101 W. Chestnut Street, Louisville, Ky.

Brooks, Barney, B.S., M.D., Associate in Clinical Surgery, Washington University School of Medicine, ^918 Forest Park Boulevard, St. Louis, Mo.

Brown, A. J., A. B., M.D. , Assistant Professor of Surgery, University of Nebraska Medical College, 402 City Nat'l Bank Bldg., Omaha, Neb.

Browning, William, Ph.B., ^LD., Professor of Nervous and Mental Diseases, Long Island College Hospital, 54 Lefferts Place, Brooklyn, N. Y.

Bryce, Thomas H., M.A., M.D., Professor of Anatomy, University of Glasgow, No. 2, The University, Glasgoiv, Scotland.

Bullard, H. Hays, A.M., Ph.D., M.D., Professor of Pathology, Western University Medical School, London, Canada.

Bunting, Charles Henry, B.S., M.D., Professor of Pathology, University of Wisconsin, Madison, Wis.

Burr, Harold Saxton, Ph.D., Assistant Professor of Anatomy, School of Medicine, Yale University, 150 York Street, Neiv Haven, Conn.

Burrows, Montrose T., A.B., M.D., Associate Professor of Experimental Surgery, Director of Research Laboratories, Barnard Free Skin and Cancer Hospital, Washington University Medical School, St. Louis, Mo.

THE ANWTOMIC.^L- RECORD, VOL. 21, NO. 1


98 AMERICAN ASSOCIATION OF ANATOMISTS

Byrnes, Charles M., B.S., M.D., Associate in Clinical Neurology, Johns Hopkins Medical School, 207 East Preston Street, Baltimore, Md.

Cameron, John, M.D., D.Sc, F.R.S.E., Professor of Anatomy, Dalhousie Medical College, Halifax, Nova Scotia.

Campbell, William Francis, A.B., MD , Professor of Anatomy and Histology, Long Island College Hospital, 334- Clinton Avenue, Brookhjn, N. Y.

Cardwell, John C, M.D., Professor of Physiology, Long Island College Hospital, Polhemus Memorial Clinic, Brooklyn, N. Y.

Carey, Eben J., M.S., Sc.D., Professor of Anatomy, Marquette University School of Medicine, Milwaukee, Wisconsin.

Carpenter, Frederick Walton, Ph.D., Professor of Biology, Trinity College, Hartford, Conn.

Carter, James Thornton, D.D.S., Research Assistant, Department of Zoology, University College, 1 Hanover Square, London, W. C. 1, England.

Carver, GailL., A.B., A.M., West Lake. Ga.

Casamajor, Louis, A.M., M.D., Profes.sor of Neurology, Columbia University, J^37 West 59lh Street, New York City.

Cash, James Robert, A.M.,M.D., Instructor in Pathology, Johns Hopkins Medical School, 20 East Ml. Vernon Place, Baltimore, Md.

Chagas, Carlos P., M.D., Professor of Histology and Pathology, Bello Horizonte Medical School, Minas-Geraes, Brazil, South America.

Chambers, Robert, Jr., A.M., Ph.D., Assistant Professor of Anatomy, Cornell University Medical College, New York City.

Chapman, W. B., A.B., M.D., Instructor in Anatomy, Department of Anatomy, Washington University Medical School, St. Louis, Mo.

Charlton, Harry Hayward, A.M., Ph.D., Assistant Professor of Anatomy, Department of Anatomy, University of Missouri, Columbia, Mo.

Cheever, David, A.B., M.D., Assistant Professor of Surgery and Associate in Anatomy, Harvard Medical School, 721 Huntington Avenue, Boston, Mass.

Chidester, Floyd E., A.M., Ph.D., Associate Professor of Zoology, University of West Virginia, Morgantown, West Virginia.

Child, Charles INIanning, M.S., Ph.D., Professor of Zoology, Zoological Laboratory, University of Chicago, Chicago, III.

Chillingworth, Felix P., M.D., Professor of Physiology and Experimental Pharmacology, Tufts Medical College, 416 Huntington Ave., Boston, Mass.

Clark, Elbert, Ph.D., M.D., Associate Professor of Anatomy, University of Chicago, Chicago, HI.

Clark, Eleanor Linton, A.M., Research Worker, Department of Anatomy, University of Missouri, I4O8 Rosemary Lane, Columbia, Mo.

Clark, Eliot R., A.B., M.D., (Ex. Com. '16-'19), Professor of Anatomy, University of Missouri, Columbia, Mo.

CoE, Wesley R., Ph.D., Professor of Biology, Yale University, Osborne Zoological Laboratory, New Haven, Conn.

Coghill, George E., M.S., Ph.D., Professor of Anatomy and Head of Department, University of Kansas Medical School, Department of Anatomy, University of Karisas, Laivrence, Kan.

CoHN, Alfred E., A.B., M.D., Member, Rockefeller Institute for Medical Research, N^ew Y'ork City, N'. Y.


PROCEEDINGS 99

CoxANT, William Merritt, A.B., M.D., Professor of Clinical Surgery, 486

Commonivealth Avenue, Boston, Mass. CoNEL, Jesse LeRoy, A.M., Ph.D., Assistant Professor of Anatomy, New York

University and Bellevue Hospital Medical College, 338 East 26th Street, New

York City. CoxGDON, Edgar Davidson, Ph.D., Assistant Professor of Anatomy, Leland

Stanford University, School of Medicine, 330 Coleridge Avenue, Palo A Ito, Calif. CoNKLiN, EdwIxX Graxt, A.M., Ph.D., Sc.D., Professor of Biology, Princeton

University, 139 Broadmead Avenue, Princeton, N. J. Corner, George W., A.B., M.D., Associate Professor of Anatomy, Anatomical

Laboratory, Johns Hopkins Medical School, Baltimore, Md. Corning, H. K., M.D., Professor of Anatomy, University of Bdle, Anatomische

Anstalt, Bdle, Switzerland. Cowdrt, Edmund V., Ph.D., Professor of Anatomy, Department of Anatomy,

Peking Union Medical College, Peking, China. Craig, Joseph David, A.M., M.D., 12 Ten Broeck Street, Albany, N. Y. Craigie, E. Horxe, Ph.D., Lecturer in Comparative Anatomy, Department of

Biology, University of Toronto, Toronto, Canada. Crile, George W., A.M., M.D., LL.D., F.A.C.S., Professor of Surgery, Western

Reserve University, Cleveland Clinic, 93rd and Euclid, Cleveland, Ohio. Crosbt, Elizabeth Caroline, Ph.D., Superintendent of Schools, Petersburg,

Mich. CtJLLEN, Thomas S., M.B., 20 E. Eager Street, Baltimore, Md. Cummins, Harold, A.B., Assistant Professor of Anatomy, Tulane University

Medical School, Department of Anatomy, Sta. 20, Neiv Orleans, La. Cunningham, Robert S., A.M., M.D., Associate in Anatomy, Johns Hopkins

Medical School, Baltimore, Md. Curtis, George M., A.M., Ph.D., Professor of Anatomy and Director of the

Anatomical Department, Vanderbilt University Medical School, Nashville,

Tenn. Dahlgren, Ulric, A.B., M.S., Professor of Biology, Princeton University, 204

Guyot Hall, Princeton, N. J. Danchakoff, Vera, M.D., Assistant Professor of Anatomy, Columbia University, 437 W. 59th Street, New York City. Danforth, Charles Haskell, A.M., Ph.D., Associate Professor of Anatomy,

Washington University Medical School, St. Louis, Mo. Darrach, William, A.M., M.D., Associate Professor of Surgery and Dean College of Physicians and Surgeons, Columbia University, 437 West 59th Street,

Neio York City. Dart, Raymond A., M.B., Ch.M., M.Sc, Demonstrator in Anatomy, University

College, Gower St., London, W. C. 1, England. Temporary Address: Johns

Hopkins Medical School, Baltimore, Md. Davis, Carl L., M.D, Professor of Anatomy, University of Maryland, Hale thorpe, Md. Davis, David M., B.S., M.D., Associate in Urology and Pathologist, Brady

Urological Institute, Johns Hopkins Hospital, Baltimore, Md. Davis, Warren B., M.D., Instructor in Anatomy, Jefferson Medical College,

135 S. 18th Street, Philadelphia, Pa.


100 AMERICAN ASSOCIATION OF ANATOMISTS

Dawson, Alden B., Ph.D., Assistant Professor of Microscopical Anatomy,

Loyola University Medical School, 706 S. Lincoln St., Chicago, III. Dean, Bashford, A.M., Ph.D., Professor of Vertebrate Zoology, Columbia

University, Curator of Fishes and Reptiles, American Museum Natural

History, Riverdale-on-Hudson, New York City. De Carlo, John, M.D., Instructor in Topographic and Applied Anatomy, Jefferson Medical College, 1124- Ellsworth St., Philadelphia, Pa. Dendy, Arthur, D.Sc, F.R.S., Professor of Zoology, University of London,

King's College, Strand W. C, London, England. Detwiler, Samuel Randall, A.M., Ph.D., Associate in Anatomy, Anatomicai

Laboratory, Peking Union Medical College, Peking, China. Dixon, A. Francis, M.B., Sc.D., University Professor of Anatomy, Trinity

College, 73 Grosvenor Road, Dvhlin, Ireland. DoDDS, Gideon S., A.M., Ph.D., Associate Professor of Histology and Embryology, West Virginia University Medical School, Morgantown, W. Va. DoDSON, John Milton, A.M., M.D., Dean and Professor of Medicine, Rush

Medical College, University of Chicago, 58.17 Blackston Avenue, Chicago, III. Dolley, D. H., A.m., M.D., Professor of Pathology, University of Missouri,

Columbia, Mo. Donaldson, Henry Herbert, Ph.D., D.Sc. (Ex. Com. '09-'13, Pres. '16-'17),

Professor of Neurology, The Wistar Institute of Anatomy and Biology, Woodland Avenue and 36th Street, Philadelphia, Pa. Donaldson, John C, Ph.B., M.D., Assistant Professor of Anatomy, University

of Cincinnati Medical College, The Maplewood, Clifton, Cincinnati, Ohio. Downey, Hal, A.M., Ph.D., Professor of Histology, Department of Animal

Biology, University of Minnesota, Minneapolis, Minn. DuBREUiL, Georges, M.D., Professor of Anatomy, Faculte de Medicine, Place

de la Victoire, Bordeaux, France. DuESBURG, Jules, M.D., Professor of Anatomy, University of Liege, 22 qusi

Mativa, Liege, Belgium. Dunn, Elizabeth Hopkins, A.M., M.D., Woods Hole, Mass. Eaton. Paul Barnes, A.B., M.D., Instructor Bacteriology, School of Hygiene

and Public Health, Johns Hopkins University, 310 W. Monument Street,

Baltimore, Md. EccLES, Robert G.. M.D., Phar.D., 681 Tenth Street, Brooklyn, N. Y. Elwyn, Adolph, A.m., Assistant Professor of Anatomy, Columbia University,

437' West 59th Street, New York City. Emmel, Victor E., M.S., Ph.D., Associate Professor of Anatomy, Department

of Anatomy, University of California, Berkeley. Calif. Erdmann, C. a., M.D., Associate Professor of Ai)plied Anatomy, Institute of

Anatomy, University of Minnesota, Minneapolis, Minn. EssiCK, Charles Rhein, B.A., M.D., 520 Franklin Street, Reading, Pa. Evans, Herbert McLean, B.S., M.D., (Ex-Com. '19-), Professor of Anatomy,

University of California, Berkeley, Calif. Evans, Thomas Hor.\ce, M.D., Associate Professor of Anatomy, Long Island

College Hospital, Henry and Amity Streets. Brooklyn, N. Y. Eycleshymer, Albert Chauncey, Ph.D., M.D., Professor of Anatomy, Medical

College, University of Illinois, Honore and Congress Streets, Chicago, III.


PROCEEDINGS 101

Fawcett, Edward, INI.D., Professor of Anatomy, University of Bristol, Bristol, England.

Ferris, Harry Burr, A.B., M.D., Hunt Professor of Anatomy, Medical Department, Yale University, 395 St. Ronan Street, Neic Haven, Conn.

Fetterolf, George, A.B., M.D., Sc.D., Assistant Professor of Anatomy, University of Pennsylvania, 2047 Chestnut Street, Philadelphia, Pa.

FixNEY, Theodora Wheeler, A.B., M.D., Mayo Clinic, Rochester, Minn.

Firket, Jean, M.D., Instructor in Anatomy, Johns Hopkins Medical School, Baltimore, Md.

FiscHELis, Philip, M.D., Professor of Histology and General Pathology, Philadelphia Dental College of Temple University, 828 North 5th Street, Philadelphia, Pa.

Ford, Francis C., A.B., M.D., Professor of Anatomy, Hahnemann Medical College and Hospital of Chicago, 2811 Cottage Grove Avenue, Chicago, III.

Formax, Jonathan, A.B., M.D., 394 East Town St., Columbus, Ohio.

Frassetto, Fabio, M.D., Ph.D., Director Anthropological Institute, University of Bologna, Bologna, llnl.y.

Frazer, John Ernest, M.D., F.R.C.S., Professor of Anatomy, University of London, St. Mary's Hospital Medical School, London, W. England.

French, H. E., M.S., M.D., Professor of Anatomy and Dean of the School of Medicine, University of North Dakota, Grand Forks, North Dakota.

Gage, Simon Henry, B.S. (Ex. Com. '06-'ll), Professor of Histology and Embryology, Emeritus, Stimson Hall, Cornell University, Ithaca, N. Y.

Gallaudet, Bern Budd, A.M., M.D., Assistant Professor of Anatomy, Columbia University, Consulting Surgeon Bellevue Hospital, 105 East 19th Street. Neu' York City.

Garcia, Arturo, A.B., M.D., Professor of Anatomy College of Medicine and Surgery, Manila, Philippine Islands.

George, Wesley Critz, A.M., Ph.D., Associate Professor of Histology and Embryology, University of North Carolina Medical School, Chapel Hill, North Carolina.

Gibson, G. H., M.D., Stipendiary Magistrate, ^Vaitangi Chatham Islands, New Zealand.

GiLLASPiE, C, M.D., Professor of Anatomy, University of Colorado, Boulder, Colo.

Globus, J. H., B.S., M.D., Research Fellow in Neuropathology, Mt. Sinai Hospital, 58 East 94th Street, New York City.

Gould, Harley Nathan, A.M., Ph.D., Professor of Biology, Wake Forest College, Wake Forest, N. C.

Grant, J. C. Boileau, M.D., Ch.B., F.R.C.S., Professor of Anatomy, U7iiversity of Manitoba Medical College, Winnipeg, Canada.

Graves, William W., M.D., Professor of Nervous and Mental Diseases, St. Louis University School of Medicine, Metropolitan Building, St. Louis, Mo.

Greene, Charles W., A.M., Ph.D., Professor of Physiology and Pharmacology, Universit}' of Missouri, 8I4 Virginia Avenue, Columbia, Mo.

Greenman, Milton J., Ph.B., M.D., Sc.D., Director of The Wistar Institute of Anatomy and Biology, 36th Street and Woodland Ave7iue, Philadelphia, Pa.


102 AMERICAN ASSOCIATION OF ANATOMISTS

Gregory, William King, A.M., Ph.D., Curator of Comparative Anatomy, American Museum of Natural History, 77th Street and Central Park West, New York City.

GuDERNATSCH, J. F., Ph.D., 58 East 94th Street, New York City.

Guild, St.\cy R., A.M., Ph.D., Assistant Professor of Anatomy, Medical School, University of Michigan, 562 South Seventh Street, Ann Arbor, Mich.

GuYER, Michael F., Ph.D., Professor of Zoology, University of Wisconsin, Madison, Wis.

Halsted, William Stewart, M.D., Sc.D., LL.D., F.R.C.S., Professor of Surgery, Johns Hopkins University, Surgeon-in-Chief, Johns Hopkins Hospital, 1201 Eutaw Place, Baltimore, Md.

Hamann, Carl A., M.D. (Ex. Com. '02-'04), Professor of Applied Anatomy and Clinical Surgery, Western Reserve University, U6 Osborne Building, Cleveland, Ohio.

HARDESTY,IR^^^•G, Ph.D., Sc.D. (Ex. Com. '10 and '12-15), Professor of Anatomy and Head of Department of Anatomy, School of Medicine, Tulane University, P. 0. Station 20, New Orleans, La.

Hare, Earl R., A.B., M.D., F.A.C.S., 7S0 LaSalle Building, Minneapolis, Minn.

Harrison, Ross Granville, Ph.D., M.D., Sc.D. (Pres. '12-'14), Bronson Professor of Comparative Anatomy, Osborn Zoological Laboratory, Yale University, New Haven, Conn.

Hartman, Carl G., Ph.D., Associate Professor of Zoology, University of Texas, Austin, Texas.

Harvey, Basil Coleman Hyatt, A.B., M.B., Professor of Anatomy, University of Chicago, Department of Anatomy, University of Chicago, Chicago, III.

Hatai, Shinkishi, Ph.D., Associate Professor of Neurology, The Wistar Institute of Anatomy and Biology, 36th Street and Woodland Avenue, Philadelphia, Pa.

Hausman, Loxtis, A.B., M.D., Instructor in Psychiatry, Johns Hopkins Hospital, Baltimore, Md.

Hazen, Charles Morse, A.M., M.D., Professional Building, Fifth and Franklin Streets, Richmond, Va.

Heisler, John C, M.D., Professor of Anatomy, University of Pennsylvania, S829 Walnut Street, Philadelphia, Pa.

Heldt, Thomas Johanes, A.M., M.D., Passed Assistant Surgeon (Reserve) U. S. Public Health Service, 415 E. Broadway, Waukesha, Wis.

Hemler, William Francis, M.D., Professor of Histologj' and Embryology, Georgetown University, 13S0 East Capitol Street, Washington, D. C.

Herrick, Charles Judson, Ph.D. (Ex. Com. '1^'17), Professor of Neurology, University of Chicago, Laboratory of Anatomy, University of Chicago, Chicago, III.

Hertzler, Arthur E., A.M., M.D., Ph.D., F.A.C.S., Professor of Surgery, University of Kansas, Halstead, Kansas.

Heuser, Chester H., A.M., Ph.D., Associate in Anatomy, Johns Hopkins Medical School, Baltimore, Md.

Hew-son, Addinell, A.m., M.D., F. A.C.S., Professor of Anatomy, Graduate School of Medicine, University of Pennsylvania, Professor of Anatomy and Histology, Temple University, 2120 Spruce St., Philadelphia, Pa.


PROCEEDINGS 103

Hill, Eben Claytox, A.B., M.D., Instructor in Anatomy, Johns Hopkins Medical School, Baltimore, Md.

Hill, Howard, M.D., 1334 Rialto Building, Kansas City, Mo.

Hill, James Peter, D.Sc, F.R.S., Jodrell Professor of Zoology, and Comparative Anatomy, University of London, Ihiiversity College, Gower Street, London, W. C. 1, England.

Hilton, William A., Ph.D., Professor of Zoology, Pomona College, Director Lagiina Marine Laboratory, Claremont, Calif.

Hines, Marion, A.B., Ph.D., Instructor in Anatomy, Department of Anatomy, University of Chicago, Chicago, III.

Hoffman, Clarence, M.D., Demonstrator in Anatomy, Jefferson Medical College, 1621 Pine St., Philadelphia, Pa.

Holt, Caroline M., A.M., Ph.D., Assistant Professor of Biology, Simmons College, 35 Irma Avenue, Watertown, Mass.

Hooker, Davenport, M.A., Ph.D., Professor of Anatomy, School of Medicine, University of Pittsbiirgh, Pittsbtirgh, Pa.

Hopewell-Smith, Arthur, L.R.C.P., M.R.C.S., L.D.S., Professor of Dental Histology and Comparative Odontology, University of Pennsylvania Dental College, Philadelphia, Pa.

Hopkins, Grant Sherman, Sc.D., D.V.M., Professor Comparative Veterinary Anatomy, Cornell University, Ithaca, N. Y.

HosKiNS, Maragert Morris, Ph.D., Instructor in Histology, Richmond College of Medicine, Richmond, Va.

HowDEN, Robert, M.A., M.B., CM., D.Sc, Professor of Anatomy, University of Durham, 14 Burdon Terrace, Newcastle-upon-Tyne, England.

HowLAND, Ruth B., Ph.D., Professor of Biology, Siccet Briar College, Sweet Briar, Va.

HrdliCka, Ales, Ph.D., M.D., Curator, Division of Physical Anthropology, United States National Museum, Washington, D. C.

Huber, G. Carl, M.D. (Second Vice-Pres. 'OO-'Ol, Secretary-Treasurer '02-'14, Pres. '14-'16, Ex. Com. '20), Professor of Anatomy and Director of the Anatomical Laboratories, University of Michigan, 1330 Hill Street, Ann Arbor, Mich.

HuGHSON, Walter, S.B., ]M.D., Assistant in Anatomy, Johns Hopkins Medical School, Baltimore, Md.

Hunter, Oscar B., M.D., Professor of Pathology and Bacteriology, George Washington Medical School, 1335 H St., N.W., Washington, D. C.

Huntington, George S., A.M., M.D., D.Sc, LL.D. (Ex. Com. '95-'97, '04-'07, '18-, Pres. '99-'03), Professor of Anatomy, Columbia University, 437 West 59th Street, New York City.

Ingalls, N. William, B.S., M.D., Associate Professor of Anatomy, School of Medicine, Western Reserve University, 1353 East 9th Street, Cleveland, Ohio.

Ingvar, Sven, M.D., Docent in Neurology, University of Lund, Lund, Sweden.

Inouye, Michio, ]\I.D., Professor of Anatomy, Tokyo Imperial University, Tokyo, Japan.

Jackson, Clarence M., M.S., M.D. (Ex. Com. '10-'14, Vice-Pres. '16-'17), Professor and Director of the Department of Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn.


104 AMERICAN ASSOCIATION OF ANATOMISTS

Jenkins, George B., M.D., Professor of Anatomy, George Washington University Medical School, Washington, D. C.

Job, Theslb T., M.S., Ph.D., Associate Professor of Anatomy, Loyola University School of Medicine, 706 S. Lincoln St., Chicago, III.

Johnson, Charles Eugene, A.M., Ph.D., Assistant Professor of Zoology, Department of Zoology, University of Kansas, Lawrence, Kansas.

Johnson, Franklin P., A.M., Ph.D., M.D., Associate Professor of Anatouw, University of Missouri, Johns Hopkins Medical School, Baltimore, Md.

Johnson, Sydney E., M.S., Ph.D., Associate in Anatomy, Northwestern University Medical School, 24^1 So^lth Dearborn Street, Chicago, III.

Johnston, John B., Ph.D., Professor of Comparative Neurologj^ University of Minnesota, Minneapolis, Minn.

Johnston, Thomas Baillie, M.B., Ch.B., Professor of Anatom}^, University of London, Guy's Hospital Medical School, London, S. E. 1., England.

Jordan, Harvey Ernest, A.M., Ph.D. (Ex. Com. '18-), Professor of Histology and Embryology, University of Virginia, S4 University Place, Charlottesville, Va.

Kampmeier, Otto Frederick, A.B., Ph.D., Associate Professor of Anatomj', College of Medicine, University of Illinois, Chicago, III.

Kappers, Cornelius Urbo Ariexs, M.D., Director of the Central Institute for Brain Research of Holland, Mauritskade 61, Amsterdam, Holland.

Keegan, John J., A.M., M.D., Assistant Professor of Pathology, University of A ebraska. College of Medicine, Omaha, A ebraska.

Keiller, William, L.R.C.P. and F.R.C.S. Ed. (Second Vice-Pres. '9S-'99), Professor of Anatomy, Medical Department University of Te.xas. State .Medical College, Galveston, Texas.

Keith, Arthur, M.D., LL.D., F.R.C.S., F.R.S., Hunterian Professor of Anatomy, Royal College of Surgeons, Lincoln's Inn Fields, London, W.C.2, England.

Kernan, John D. Jr., A.B., M.D., Assistant in Anatomy, Columbia University, 156 East 79th Street, New York City.

Kerr, Abram T., B.S., M.D. (Ex. Com. '10-'14), Professor of Anatomy, Cornell University Medical College. Ithaca, N. Y.

Key, J. Albert, B.S., M.D., 656 Huntington Ave., Boston, Mass.

KiNGERY, Hugh McMillan, A.M., Ph.D., Assistant Professor of Anatomy, School of Medicine, University of Colorado, Boulder, Colo.

Kingsbury, Benjamin F., Ph.D., M.D., Professor of Histology and Embryology, Cornell University, 2 South Avenue, Ithaca, N. Y.

Kingsley, John Sterling, Sc.D., Professor of Zoology, University of Illinois, Urbana, III.

King, Helen Dean, A.M., Ph.D., Assistant Professor of Embrj^ology, The Wislar Institute of Anatomy, 36th Street and Woodland Avenue, Philadelphia, Pa.

Kirkham, William Barui, Ph.D., Research Embrj-ologist, 103 Everit Street, New Haven, Conn.

Knower, Henry McE., A.B., Ph.D., (Ex. Com. '11-'15), Professor of Anatomy, Medical College, University of Cincinnati, Eden Avemie, Cincinnati, Ohio


PROCEEDINGS 105

Kocii, John- C, B.S., M.D., Board of Health, Orthopedic Staff, Harper Hospital, 97 Euclid Avenue, East, Detroit, Mich.

KoFoiu, Charles Atwood, Ph.D., Sc.D., Professor of Zoology, University of California, De-partment of Zoology, University of California, Berkeley, Calif.

Kraxjse, Allen Kramer, A.M., M.D., Associate Professor of Medicine, Johns Hopkins University, Johns Hopkins Hof<pital, Baltimore, Md.

Kudo, Toktjyasu, ^I.D., Professor of Anatomj', Niigata Medical College, hiigata, Japan.

KuxiTOMO, Kanae, M.D , Professor of Anatomy, Anatomical Institute, Nagasaki Medical School, Nagasaki, Japan.

Kunkel, Beverly Waugh, Ph.B., Ph.D., Professor of Biology, Lafayette College, Easion, Pa.

KuNTZ, Albert, Ph.D., M.D., Professor of Anatomy and Biology, St. Louis University Medical School, H02 South Grand Ave., St. Louis, Mo.

KuTCHiN,' Mrs. Harriet Lehmann, A.M., "The MaplewoOd," Green, Lake, Wis.

Lambert, Adriax V. S., A.B., M.D., Associate Professor of Surgery, Columbia University, 168 East 71st Street, New York City.

Landacre, Francis Leroy, Ph.D., Professor of Anatomy, Ohio State University, 2026 Inka Avenue, Columbus, Ohio.

Lane, Michael Andrew, B.S., 122 South California Avenue, Chicago, III.

Laesell, Olaf, Ph.D., Associate Professor of Zoology, Zoological Laboratory, A orthu-estern University, Evanston, III.

Latimer, Homer B., A.M., Professor of Vertebrate Anatomj^ University of Nebraska, 1226 South 26th Street, Lincoln, Neb

Latta, John S., A.B., Ph.D., Instructor in Histology and Embryology, Sti?7ison Hall, Cornell University, Ithaca, N . Y.

Laurens, Henry, A.M., Ph.D., Assistant Professor of Biology, Yale University, Osborne Zoological Laboratory, New Haven, Conn.

Lee, Thomas G., B.S., M.D. (Ex. Com. 'OS-'IO, Vice-Pres. '12-'14), Professor of Comparative Anatomy, Institute of Anatomy, University of Minnesota, Min?ieapolis, Minn.

Leidy, Joseph, Jr., A.M., M.D., 1319 Locust Street, Philadelphia, Pa.

Levi, Giuseppe, M.D., Professor of Anatomy, University of Torino, Torino, Italy.

Lewis, Dean D., M.D., Assistant Professor of Surgery, Rush Medical College, Peoples Gas Building, Chicago, III.

Lewis, Frederic T., A.M., M.D. (Ex. Com. '09-'13, Vice-Pres. '14-'16), Associate Professor of Embryology, Harvard Medical School, Boston, Mass.

Lewis, Margaret Reed, M.A., Collaborator, Department of Embryology, Carnegie Institution of Washington, Johns Hopkins Medical School, Baltimore, Md.

Lewis, Warren Harmon, B.S., M.D. (Ex. Com. '09-'ll, '14-'17), Research Associate Department of Embryologj', Carnegie Institution, Professor of Physiological Anatomy, Johns Hopkins Medical School, Baltimore, Md.

LiLLiE, Frank Rathay, Ph.D., Sc.D., Professor of Embryology, Chairman of Department of Zoology, University of Chicago; Director Marine Biological Laboratory, Woods Hole, Mass., University of Chicago, Chicago, III.

LiNEBACK, Paul Eugene, A.B., M.D., Professor of Histology and Embryology, Atlanta Medical College, Emory University, Ga.


106 AMERICAN ASSOCIATION OF ANATOMISTS

LiPSHtTTZ, Benjamin, M.D., Instructor in Neuro-anatomy, Jefferson Medical

College, 1007 Spruce St., Philadelphia, Pa. LocY, William A., Ph.D., Sc.D., Professor of Zoology and Director of the

Zoological Laboratory, Northwestern University, Evanston, III. LoEB, Hanaxj \Yolf, A.M., M.D., Dean and Professor of the Diseases of the Ear, Nose and Throat, St. Louis University, 537 North Graiid Avenue, St. Louis, Mo. Lord, Frederic P., A.B.,M.D., Professor of Anatomy, Dartmouth Medical School,

Hanover, N. H. LowREY, Lawson Gentry, A.M., M.D., Assistant Professor of Psychiatry; Assistant Director Psychopathic Hospital, University of Iowa, Iowa City, Iowa. Macklin, C. C, M.D., Associate Professor of Anatomy, Johns Hopkins Medical

School, Baltimore, Md. McClung, Clarence E., A.M., Ph D., Professor of Zoology and Director of the Zoological Laboratory (Chairman Division of Biology and Agriculture National Research Council 1919-1920), University of Pennsylvania, Philadelphia, Pa. McClure, Charles Freeman Williams, A.M., Sc.D. (Vice-Pres. 'lO-'ll, Ex. Com. '12-'16, Pres. '20), Professor of Comparative Anatomy, Princeton University, Princeton, N. J. McCoTTER, RoLLO E., M.D., Professor of Anatomy, Medical Department, University of Michigan, 104S Ferdon Road, Ann Arbor, Mich. McFarland, Frank Mace, A.M., Ph.D., Professor of Histology, Leland Stanford Junior University, 2 Cabrillo Avenue, Stanford University, Calif. McGiLL, Caroline, A.M., Ph.D., :\I.D., Physician, 52 W. Quartz, Butte, Mont. McIntosh, William, A.B., A.M., Student of Medicine, Johns Hopkins Medical

School, Baltimore, Maryland. McJuNKiN, F. A., M.A., M.D., Associate Professor of Pathology, Washington

University Medical School, St. Louis, Mo. McKiBBEN, Paul S., Ph.D., Professor of Anatomy, Western University Medical

School, London, Canada

McMuRRicH, James Playfair, A.M., Ph.D., LL.D. (Ex. Com. '06-'07, '17 Pres. '08-'09), Professor of Anatomy, University of Toronto, Toronto, Canada.

Magath, Thomas Byrd, M.S., Ph.D., M.D., Assistant Professor of Clinical

Bacteriology and Parasitologist, University of Minnesota, Mayo Clinic,

Rochester, Minn.

Mangum, Charles S., A.B., M.D., Professor of Anatomy, University of North

Carolina, Chapel Hill, N. C. Malone, Edward F., A.B., M.D., Professor of Histology, University of Cincinnati, College of Medicine, Eden Avenue, Cincinnati, Ohio. Mark, Edward Laurens, Ph.D., LL.D., Hersey Professor of Anatomy and Director of the Zoological Laboratory, Harvard University, 109 Irving Street, Cambridge, Mass. Matas, Rudolph, M.D., LL.D., Professor of Surgery, Tulane University of

Louisiana, 2255 St. Charles Avenue, Neiv Orleans, La. Mavor, James Watt, M.A., Ph.D., Assistant Professor of Zoology, Union College, Schenectady, N. Y.


PROCEEDINGS 107

Maximow, Alexander, M.D , Professor of Histology and Embryology at the Imperial Military Academy of Medicine, Botkinskja 2, Petrograd, Russia.

Mead, Harold Tupper, B.A., M.S., Associate Professor of Zoology, Tulane University, New Orleans, La.

Meaker, Samuel R., A.B., M.D., Teaching Fellow, Department of Anatomy, Harvard Medical School, Boston, Mass.

Mellus, Edward Lindon, M.D., 12 Fuller Street, Brookline, 47, Mass.

Mercer, William F., Ph.M., Ph.D., Professor of Biology, Ohio University, Box S84, Athens, Ohio.

Metheny, D. Gregg, M.D., L.R.C.P., L.R.C.S., Edin., L.F.P.S., Glasg., Dispensary Navy Yard, League Island, Philadelphia, Pa.

Meyer, Adolph, M.D., LL.D., Professor of Psychiatry and Director of the Phipps Psychiatric Clinic, Johns Hopkins Hospital, Baltimore, Md.

Meyer, Arthur W., SB., M.D. (Ex. Com. '12-'16), Professor of Anatomy, Leland Stanford Junior University, 121 Waverly Street, Palo Alto, Calif.

Miller, Adam M., A.M., Professor of Anatomy, Long Island College Hospital, S35 Henry Street, Brooklyn, N. Y.

Miller, William Snow, M.D., Sc.D. (Vice-Pres. '08-'09), Professor of Anatomy University of Wisconsin, 2001 Jefferson Street, Madison, Wis.

MooDiE, Roy L., A.B., Ph.D., Associate Professor of Anatomy, University of Illinois, Medical College, Congress and Honore Streets, Chicago, III.

Moody, Robert Orton, B.S., M.D., Associate Professor of Anatomy, University of California, 2826 Garber Street, Berkeley, Calif

Morrill, Charles V., A.M., Ph.D., Assistant Professor of Anatomy, Cornell University Medical School, 1st Avenue and 28th Street, New York City.

MuLLER, Henry R., A.B., M.D., Assistant in Pathology, Cornell University Medical College, 1st Avenue and 28th Street, New York City.

Munson, John P., M.S., Ph.D., F.R.S.A., Head of the Department of Biology, Washington State Normal School, 706 North Anderson Street, Ellensburg, Washington.

Murphey, Howard S., D.V.M., Professor of Anatomy and Histology, Station A, Veterinary Buildings, Ames, Iowa.

Murray, H. A., Jr., A.M., M.D., 129 East 69th Street, New York City.

Myers, Burton D., A.M., M.D., Professor of Anatomy and Assistant Dean of the Indiana University School of Medicine, 321 A. Washington St., Bloomington, hid.

Myers, Jay A., M.S., Ph.D., M.D., Instructor in Medicine, University of Minnesota, 303 La Salle Bldg., Minneapolis, Minn.

Myers, Mae Lichtenwalner, M.D., Associate Professor of Anatomy and Director of the Laboratories of Histology and Embryology, Women's Medical College of Pennsylvania, North College Avenue and 21st Street, Philadelphia, Pa.

Nachtrieb, Henry Francis, B.S., Professor of Animal Biology and Head of the Department, University of Minnesota, Minneapolis, Minn.

Nanagas, Juan Cancia, M.D., Assistant Professor of Anatomy, College of Medicine and Surgery, Manila, Philippine Islands. (Temporary address — Dept. of Anatomy, Johns Hopkins Medical School, Baltimore.)


108 AMERICAN ASSOCIATION OF ANATOMISTS

Neal, Herbert Vincent, A.M., Ph.D., Professor of Zoology, Tufts College, Tufts College, 57, Mass.

NiCHOL.\s, John Spangler, B.S., ]M.S., University Fellow in Zoology, Oshorn Zoological Laboratory, Yale University, New Haven, Conn.

NoB.\CK, GcsTAVE J., B.S., M.A., Instructor in Anatomy, Anatomical Institute, University of Minnesota, Minneapolis, Minn.

NoxiDEZ, Jos6 F., Sc.M., Sc.D., Instructor in Anatomy, Cornell University Medical College, 1st Avenue and 28th Street, New York City.

Norris, H. W., A.B., Professor of Zoology, Grinnell College, Grinnell, Iowa.

O'DoNOGHUE, Charles H., D.Sc, F.Z.S., Professor of Zoology, University of Manitoba, Winnipeg, Canada.

Okajima, K., M.D., Professor of Anatomy, Keio University Medical College, Tokio, Japan.

OsTERUi), Hjalmar L., A.B., A.M., Instructor in Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn.

Ott, Martin D., A.B., Institute of Anatomy, University of Minnesota, Minneapolis, Minn.

Owen, William 0., M.D., Colonel U. S. A. M. C. (Retired), 2719 Ontario Road, Washington, D. C.

Painter, Theophilus S., Ph.D., Adjunct Professor of Zoology, School of Zoology, University of Texa-'i, Austin, Texas.

Papanicolaou, George N., Ph.D., M.D., Instructor in Anatomy, Cornell University Medical College, 28th Street and First Avenue, New York City.

Papez, James Wencelas, B.A., M.D., Assistant Professor of Anatomy and Neurology, Cornell University Medical College, Ithaca, N. Y.

Parker, George Howard, D.Sc, Professor of Zoology, Harvard University, 16 Berkeley Street, Cambridge, Mass.

Paton, Stewart, A.B., M.D., Lecturer in Neurobiology, Princeton University, Princeton, N. J.

Patten, Bradley Merrill, A.M., Ph.D., Assistant Professor of Histology and Embryology, School of ^Medicine, Western Reserve University, 1353 East 9th Street, Cleveland, Ohio.

Patten. William, Ph.D , Professor of Zoology, Dartmouth College, Hanover, N. H.

Patterson, John Thomas, Ph.D., Professor and Chairman of the School of Zoology, University of Texas, University Station, Austin, Texas.

Perkins, Orman C, A.M., Assistant Professor of Anatomy, Long Island College Hospital, 3.35 Henry St., Brooklyn, New York.

Pfeiffer, John A. F., M.A., M.D., Ph.D., Physician and Pathologist, 1421 Edmondson Avenue, Baltimore, Md.

Piersol, George A., M.D., Sc.D. (Vice-Pres. '93-'94, '98-'99, '06-'07, Pres. 'lO-'ll), Professor of Anatomy, University of Pennsylvania, 4724 Chester Avenue, Philadelphia, Pa.

Piersol, William Hunter, A.B., M.B., Associate Professor of Histology and Embryology, University of Toronto, 85 Dunvegan Road, Toronto, Canada.

Ping, Chi, Ph.D., Government Teachers College, Naiiking, China.

PoHLMAN. Augustus G., M.D., Professor of Anatomy, St. Louis University, School of Medicine, 1402 South Grand Avenue, St. Louis, Mo.


PROCEEDINGS 109

Potter, Peter, M.S., M.D., Oculist and Aurist, Murray Ilosijital, Ikitte, Montana, 4II-4IS Hennessy Building, Butte, Montana.

PoYNTER, Charles W. M., B.S. M.D., (Ex. Com. '19-), Profes.sor of Anatomy College of Medicine, University of Nebraska, 42tid and Dewey Avenue, Omaha, Nch.

Pracher, John, M.D., Pathologist, St. Mary's Hospital, Evansville, Ind.

Prentiss, H. J., M.D., M.E., Professor of Anatomy, State University of Iowa, loiva City, loiva.

Pryor, Joseph William, M.D., Professor of Anatomy and Physiology, University of Kentucky, Lexington, Ky.

Radasch, Henry E., M.S., M.D., Assistant Professor of Histology and Embryology, Jefferson Medical College, Daniel Baugh Institute of Anatomy, 11th and Clinton- Streets, Philadelphia, Pa.

Ranson, Stephen W.,M.D., Ph.D., Professor of Anatomy, Northwestern University Medical School, 2431 South Dearborn Street, Chicago, III.

Rasmtjssen, Andrew T., Ph.D., Associate Professor of Neurology, Institute of Anatomy, University of Minnesota, Minneapolis, Minn.

Reagan, Franklin P., Ph.D., Assistant Professor of Zoology, Department of Zoology, University of California, Berkeley, Calif.

Reed, Hugh D., Ph.D., Professor of Zoology, Cornell University, McGraic Hall, Ithaca, N. Y.

Reinke, Edwin E., M.A., Ph.D., Associate Professor of Biology, Vand rbilt University, Nashville, Tenn.

Retzer, Robert, M.D., Medical School, University of Pittsburgh, Pittsburgh, Pa.

Revell, Daniel Graisbbrry, A.B., M.B., Professor of Anatomy, University of Alberta, Edmonton, South, Strathcona, P. O., Alberta, Canada.

Rhinehart. D. A., A.M., M.D., Roentgenologist Little Rock City Hospital, Donaghey Bldg. . Little Rock, Ark.

Rice, Edward Loranus, Ph.D., Professor of Zoology, Ohio Wesleyan University, Delaware, Ohio.

RiNGOEN, Adolph R., A.M., Ph.D., Instructor in Animal Biology, Department of Biology, University of Minnesota. Minneapolis, Minn.

Robertson, Albert Duncan, B.A., Professor of Biology, Western University, London, Ontario, Canada.

Robinson, Arthur, M.D., F.R.C.S. (Edinburgh), Professor of Anatomy, University of Edinburgh, University, Teviot Place, Edinburgh, Scotland

Robinson, Byron L., A.B., M.A., Medical Interne, University Hospital, Minneapolis, Minn.

Rupert, R. R., M.D., Professor of Gross Anatomy, Uriiversity of Utah, Schoot of Medicine, Salt La^-". City, Utah.

Ruth, Edward S., M.D., Associate Surgeon, Children's Ho.spital, 6548i Hollywood Bldg., Los Angeles, Calif.

Sabin, Florence R., B.S., M.D., Sc.D. (Second Vice-Pres. '08- '09), Professor of Histology, Johns Hopkins Medical School, Baltimore, Md.

Sachs, Ernest, A.B., M.D., Professor of Clinical and Neurological Surgery, Washington University School of Medicine, 97 Arundel Place, St. Louis, Mo.


110 AMERICAN ASSOCIATION OF ANATOMISTS

Sansom, George Samuel, B.S., M.C., D.F.C., Honorarj' Research Assistant, Department of Zoology, University College, London, Kennel Moor, Milford, Surrey, England. Santee, Harris E., A.M., Ph.D., INI.D., Professor of Neurology, Jenner ^Medical College, 2806 Warren Avenue, Chicago, III.

ScAMMON, Richard E., Ph.D., Professor of Anatomy, Institute of Anatomy, University of Minnesota, Minneapolis, Minn.

ScHAEFER, Marie Charlotte, M.D., Associate Professor of Biology, Histology and Embryology, Medical Department, University of Texas, 705 North Pine Street, San Antonio, Texas.

ScHAEFFER, Jacob Parsons, A.M., M.D., Ph.D., Professor of Anatomy and Director of the Daniel Baugh Institute of Anatomy, Jefferson Medical College, nth and Clinton Streets, Philadelphia, Pa.

Shoemaker, Daniel M., B.S., M.D., Professor of Anatomy, Medical Department, St. Louis University, 1402 South Grand Avenue, Si. Louis, Mo.

Schulte, Hermaxn vox W., A.B., M.D. (Ex. Com. '15-'18), Professor of Anatomy and Dean, Creighton Medical College, Omaha, Neb.

Schultz, Adolph H., Ph.D., Research Associate, Carnegie Institution, Department of Embryology, Carnegie Laboratory, Johns Hopkins Medical School, Baltimore, Md.

Schmitter, Feudin-axd, A.B., M.D., Lt. Col. Med. Corps, U. S. A., 458 Delaware Avenue, Albany, N. Y.

Scott, Johx W., Ph.D., Professor of Zoology and Research Parasitologist, University of Wyoming, Laramie, Wyoming.

Scott, Katherixe Julia, A.B., M.D., Instructor in Anatomy, Department of Anatomy, University of California, Berkeley, Calif.

Selling, Lawrence, A.B., M.D., Selling Building, Portland, Ore.

Senior, H. D., M.D., D.Sc, F.R.C.S., Professor of Anatomy, New York University and Bellevue Hospital Medical College, 338 East 26th Street, New York City.

Shaxer, Ralph Faust, Ph.D., Instructor in Anatomy, Department of Anatomy, Harvard Medical School, Boston, Mass.

Sharp, Claytox, A.B., M.D., Assistant Professor Dental Histology and Embryology, Columbia University, 437 West 59th Street, New York City.

Shellshear, Joseph Lexden, ^T.B., Ch.M., Demonstrator of Anatomy, University College, Gower St., London, W. C. 1, England. (Present address — Dept. of Anatomy, Johns Hopkins Medical School, Baltimore.)

Sheppard, Hubert, M.A., Ph.D., Assistant Professor of Anatomy, University of Kansas, School of Medicine, Lawrence, Kansas.

Shields, Randolph Tucker, A.B., M.D., Professor of Histology and Embryology, School of Medicine, Shantung Christian University, Tsinan, Shantung, China.

Shimidzu, Yoshitaka, M.D., Professor of Gynecology, Nagasaki Medical College, Nagasaki, Japan

Shufeldt, R. W., M.D., Major Medical Corps, U. S. A. (Retired), 3356 Eighteenth Street, Washington, D. C.

Silvester, Charles Frederick, Captain Sanitary Corps, U. S. A., Guyot Hall, Princeton University, Princeton, N. J.


PROCEEDINGS HI

Simpson, Sutherland, M.D., D.Sc, F.R.S.E. (Edin.), Professor of Physiology, Cornell University Medical College, Ithaca, N'. Y.

Sltjder, Greenfield, M.D., Clinical Professor of Laryngology and Rhinology, Washington University Medical School, 354^ Washington A venue, St. Louis, Mo.

Smith, David T., A.B., Medical Student, Johns Hopkins Medical School, Baltimore, Md.

Smith, George Milton, A.B., M.D., Attending Surgeon, Waterbury Hospital, 111 Buckingham Street, Waterbury, Conn.

Smith, Grafton Elliot, M.A., M.D., F.R.S., Professor of Anatomy, University College, Gower St., London, W. C. 1, England.

Smith, H. P., A.B., Hooper Research Lab., 1332 Sixth Ave., San Francisco, Calif.

Smith, Philip Edward, M.S., Ph.D., Assistant Professor of Anatomy, University of California, 1513 Scenic Avenue, Berkeley, Calif.

Smith, Wilbur Cleland, M.D., Surgeon, Americus, Ga.

Snow, Perry G., A.B., M.D., Dean and Professor of Anatomy, University of Utah Medical School, Salt Lake City, Utah.

Spaulding, M. H., A.m., Assistant Professor of Zoology, University of Montana, Bozeman, Montana.

Speidel, Carl C, Ph.D., Adjunct Professor of Anatomy, University of Virginia, University, Va.

Stewart, Chester A., A.M., Ph.D., Fellow in Pediatrics, Roorn 121, Millard Hall, University of Minnesota, Minneapolis, Minn.

Stewart, Fred Waldorf, A.B., Ph.D., Instructor in Neurology, Cornell University Medical College, Ithaca, N. Y.

Stiles, Henry Wilson, M.D., Professor of Anatomy, College of Medicine, Syracuse University, 309 Orange Street, Syracuse, N. Y.

Stockard, Charles Rupert, M.S., Ph.D., Sc.D., (Secretarj'-Treasurer '14- ), Professor of Anatomy, Cornell University Medical College, New York City.

Stone, Leon Stansfield, Ph.B., Assistant in Anatomy, Medical College, Yale University, New Haven, Conn.

Stone, Robert S., B.A., Assistant in Anatomy, Peking Uiiion Medical College, Peking, China.

Stopford, John Sebastian B., ]\LD., Professor of Anatomy, University of Manchester, Manchester, England.

Stotsenburg, James M., INLD., Instructor in Anatomy, The Wistar Institute of Anatomy and Biology, Philadelphia, Pa.

Streeter, George L., A.M., M.D., (Ex. Com. 'IS-), Director Department of Embryology, Carnegie Institution of Washington, Johns Hopkins Medical School, Ballimore, Md.

Stromsten, Frank Albert, D.Sc, Associate Professor of Animal Biology, State University of Iowa, 943 Iowa Avenue, Iowa City, Iowa.

Strong, Oliver S., A.M., Ph.D., Associate Professor of Neurology, Columbia University, 437 West 59th Street, New York City.

Strong, Reuben Myron, A.M., Ph.D. (Ex. Com. '16-'19), Professor of Anatomy, Loyola University School of Medicine, 706 South Lincoln Street, Chicago, III.

Sullivan, Walter Edward, A.M., Ph.D., Assistant Professor of Anatomy, University of Wisconsin, Science Hall, Madison, Wis.


112 AMERICAN ASSOCIATION OF ANATOMISTS

SuNDWALL, John, Ph.D., M.D., Professor of Hygiene, Universitij of Minnesota,

Minneapolis, Minn. Sutton, Alan Callender, A.B., M.D., Johns Hopkins Medical School, S129

St. Paul Street, Baltimore, Md. SwETT, Francis Huntington, A.M., Assistant, Osborn Zoological Laboratory,

Yale University, New Haven, Conn. Swift, Charles H., M.D., Ph.D., Assistant Professor of Anatomy, University

of Chicago, 5632 Maryland Avenue, Chicago, III. Swingle, W. W., Ph.D., Instructor in Zoology, Yale University, New Haven,

Conn. Takenouchi, Matsuziro, M.D., Assistant Professor of Bacteriology and

Hygiene, Medical College, Imperial University of Tokio, Tokio, Japan. Terry, Robert James, A.B., M.D. (Ex. Com. '08-'12), Professor of Anatomy,

Washington University Medical School, St. Louis, Mo. Thomson, Arthur, M.A., M.B., LL.D., F.R.C.S., Professor of Anatomy, Uni rersity of Oxford, Department of Human- Anatomy , Oxford, England. Thorkelson, Jacob, M.D., Daly Bank Bldg., Anaconda, Montana. Thro, William C, A.M., M.D., Professor of Clinical Pathology, Cornell University Medical College, 28th Street and 1st Avenue, New York City. Thijringer, Joseph M., M.D., Assistant Professor of Anatomy, Tulane University, P. 0. Station 20, New Orleans, La. Thyng, Frederick Wilbur, Ph.D., Associate Professor of Anatomy, University

and Bellevue Hospital Medical College, 338 East 26th Street, Neio York

City. Tilney, Frederick, M.D., Ph.D., Professor of Neurology, Columbia University,

22 East 63rd Street, New York City. . Todd, T. Wingate, M.B., Ch.B. (Mane), F.R.C.S. (Eng.), (Vice-Pres. '20),

Professor of Anatomy, Medical Department, Western Reserve University,

1353 East 9th Street, Cleveland, Ohio. Tracy, Henry C, A.M., Ph.D., Professor of Anatomy, University of Kansas,

Lawrence, Kansas. TuppER, Paul YoER, M.D., Clinical Professor of Surgery, Washington University

Medical School, Wall Building, St. Louis, Mo. Turner, Clarence L., M.A., Ph.D., Professor of Zoology, Beloit College, Beloit,

Wisconsin. Vance, Harry Wellington, A.B., Medical Student, Johns Hopkins Medical

School, Baltimore, Md. VAN deu Horst, C. J., Ph.D., Zoologi.-ich Labor atorium, PL Muidergracht 34,

A m.'itcrdam, Holland. Van der Stricht, Omer, M.D., Professor of Histology and Embryology, University of Ghent, 71 March4 au lin, Ghent, Belgium. Waite, Frederick Clayton, A.M., Ph.D., Professor of Histolocv and Embryology, Western Reserve University School of Medicine, 1353 East 9th

Street, Cleveland, Ohio. VVallin, Ivan E., M.A., D.Sc, Professor of Anatomy, University of Colorado,

College of Medicine, Boulder, Colo. Walmsley, Thomas, M.D., Professor of Anatomy, Queens University of Belfast,

Belfast, Ireland.


PROCEEDINGS 113

Warrex, John, A.B., AI.D., Associate Professor of Anatomy, Harvard Medical School, Boston, Mass.

Waterston, David, M.A., M.D., F.R.C.S. Ed., Butte Professor of Anatomy, University of St. Andrews, St. Andrews, Fife, Scotland.

Watkins, Richard Watkin, B.S., Instructor in Anatomy, Department of Anatomy, University of Chicago, Chicago, III.

Watson, David Meredith Sears, M.Sc, Lecturer in Vertebrate Paleontology, University College, Gower St., London, W . C. 1, England.

Watson, Ernest M., A.M., M.D., Instructor in Applied Anatomy, University of Buffalo, 494 Franklin St., Buffalo, N. Y.

Watt, James Crawford, M.A., M.D., Assistant Professor of Anatomy, University of Toronto, 20 Haivthorne Avenue, Toronto, Canada.

Weed, Lewis Hill, A.M., M.D., (Ex. Com. '20), Professor of Anatomy, Johns Hopkins Medical School, Baltimore, Md.

Wegeforth, Paul, A.B., M.D., Captain M. C, U. S. A., Coronado, Calif.

Weidenreich, Franz, M.D., a.o. Professor and Prosector of Anatomy, formerly 19 Vogesen Street, Strassburg, i Els. France.

West, Randolph, A. M., M.D., College of Physicians and Surgeons, 437 West 59th Street, New York City.

White, Harry Oscar, M.D., University Club, Los Aiigeles, Calif.

Whitnall, S. E., M.A., M.D., B.Ch., Professor of Anatomy, McGill University, Montreal, Canada.

Wittenborg, a. H., M.D., Professor of Anatomy, College of Medicine, University of Tennessee, Memphis, Tenn.

Wilder, Harris Hawthorne, Ph.D., Professor of Zoology, Smith College, Northampton, Mass.

Wilhelmj, Charles M., A.B., Teaching Fellow in Anatomy, St. Louis University ^ledical School, I402 South Grand Ave., St. Louis, Mo.

Williams, James Willard, B.A., ]M.A., Professor of Biology, College of Yale in China, Changsha, Chijia.

Williams, Stephen Riggs, A.M., Ph.D., Professor of Zoology and Geology, Miami University, 300 East Church Street, Oxford, Ohio.

Willard, William A., A.]\I., Ph.D., Professor of Anatomy, University of Nebraska, College of Medicine, 42d Street and Dewey Avenue, Omaha, Neb.

Wilson, J. Gorden, M.A., M.B., CM. (Edin.), Professor of Otology, Northwestern University Medical School, 2481 S. Dearborn Street, Chicago, III.

Wilson, James Thomas, M.B., F.R.S., Challis Professor of Anatomy, University, Sydney, Australia.

Wilson, Louis Blanchard, M.D., Director of Pathology Division, Mayo Clinic and Mayo Foundation, Professor of Pathology in the University of Minnesota, Mayo Clinic, 830 W. College Sreet, Rochester, Minn.

Wislocki, George B., A.B., M.D., Associate in Anatomy, Johns Hopkins Medical School, Baltimore, Md.

WiTHERSPOON, Thomas Casey, M.D., Murray Hospital, Butte, Mont.

Woollard, Herbert T., M.D., Demonstrator of Anatomy, University College, Gower St., London, W. C. 1, England.

Worcester, John Locke, M.D., Professor of Anatomy, University of Washington, 5211-21st Avenue, N.E., Seattle, Wash.


r


\^'^


BOOKS RECEIVED

THE BLIND : Their coxdition axd the work being done for them in the United States, by Harrj^ Best, Ph. D., 764 pages, The Macmillan Company, New York, 1919.

Foreword. In the present study the field of inquiry in respect to the blind has been limited to the United States, except in so far as an account is necessary of the operations in foreign countries in the way of affording instruction to blind children and of devising a system of raised print, as an introduction to the work in this country. References are accordingly only to American sources, save as to a restricted number of publications in England dealing with the two subjects mentioned, with popular conceptions regarding the blind, and occasionally with other matters.

EMBRYOLOGY OF THE CHICK, by Bradley M. Patten, Western Reserve University, 168 pages, 182 figures, P. Blakiston's Son & Company, Philadelphia, 1920.

Preface. The fact that most courses in vertebrate embryology deal to a greater or lesser extent with the chick seems to warrant the treatment of its development in a book designed primarily for the beginning student. To a student beginning the study of embrj^ology the very abundance of information available in the literature of the subject is confusing and discouraging. He is unable to cull the essentials and fit them together in their proper relationships and is likely to become hopelessly lost in a maze of details. This book was written in an effort to set forth for him in brief and simple form the early embryology of the chick. It does not purport to treat the subject from the comparative view point, nor to be a reference work. If it helps the student to grasp the structure of the embryos, and the sequence and significance of the processes he encounters in his work on the chick, and thereby conserves the time of the instructor for interpretation of the broader principles of embrj^ology it will have served the purpose for which it was written.

THE STORY OF THE .AJMERICAN RED CROSS IN ITALY, by Charles M.

Blakewell, 254 pages, 20 Illustrations, The Macmillan Company, New York,

1920.

Introduction. The purpose of this book is not to give a detailed statistical account of Red Cross activities in Italy, — that may be found in the various Department Reports, — but rather to tell the American people who contributed so generousl}^ to the Red Cross funds the simple tale of what their dollars did in Italy. It is a great and inspiring record and one in which Americans may well take pride.


THE ANATOMICAL RECORD, VOL. 21, NO. 2


Resumen por el autor, George L. Streeter.

La emigraeion de la vesicula auditiva del renacuajo.

En el curso ordinario del desarroUo la vesicula auditiva del renacuajo experimenta una emigraeion definida, moviendose desde el sitio en el cual se desprende de la piel a una posicion mas medial y dorsal, de tal modo que eventualmente viene a situarse muy cerca de la superficie lateral del cerebro posterior, con el ap6ndice endolinfatico recubriendo el borde del delgado velo medular que forma el techo del cuarto ventriculo.

Esta particularidad, aparentemente, no es simplemente el resultado de un ajuste producido durante su desarrollo por la interaccion de los procesos mecanicos de las estructuras adyacentes, sino que se debe, al menos parcialmente, a una tendencia autostatica inherente a la vesicula misma, por medio de la cual mantiene y ajusta exactamente su posicion durante al desarrollo con relaci6n al cerebro y las estructuras que le rodean.

Translation by Jos6 F. Nonidez Cornell Medical College, New York


AUTHORS ABSTRACT OF TII'S PAPf:R ISSUED BY THE BIBL'-OGHAPHK: SEKVICE, MAT 9


MIGRATION OF THE EAR VESICLE IN THE TADPOLE DURING NORiMAL DEVELOPMENT

GEORGE L. STREETER

Department of Embryology, Carnegie Institution of Washington, Baltimore, Marylayid

ELEVEN FIGURES

In 1837 von Baer made the observation that the diaphragm is situated in the neck region in very young embryos, receiving its innervation from the cervical nerves, and that in the course of its development it acquires a more caudal position corresponding to the enlargement of the heart and lungs. This descent of the diaphragm was subsequently described in greater detail by Mall ('97). Uskow ('83) and Mall ('97) pointed out the marked shifting of position which the heart, lungs, liver, intestinal tract, and Wolffian bodies undergo during development in relation to each other and to the vertebral column. The migration of these organs in the embryo has given us the explanation of the peculiar course of their nerves of supply; for example, the inferior laryngeal, the vagus, the phrenic, and the splanchnic nerves. Kolliker ('61) showed that the shifting in position of the spinal cord produces an elongation of the spinal-nerve roots and the formation of the Cauda equina. The influence of this factor in the formamation of the filum terminale has been recently studied by Kunitomo ('18). It has been shown by Lewis ('01, '10) that such muscles as the trapezius and the eye muscles undergo considerable shifting in position between the time of their first appearance and the time when they have acquired their permanent attachments. Among others, Futamura ('06) has described the migration of the facial muscles and the consequent deflected distribution of the branches of the facial nerve. Within the central nervous system there are several instances where the

115


116 GEORGE L. STREETER

component nuclear masses exhibit a distinct migration in the course of their development (Streeter, '08; Kappers, '10). As a result of their disproportionate growth, the primary divisions of the brain shift into new positions relative to each other, and this is accompanied by an interesting adjustment on the part of the vascular drainage of these structures. Kohn ('07) and others have shown that the sympathetic gangUa undergo an extensive peripheral migration. When the places of origin of the thjTQus and thyroid glands were first discovered, it was recognized that these organs exhibit a conspicuous type of migration. Even in the case of the skeleton, it has been maintained (Rosenberg, '76) that the point of vertebral articulation of the pelvic girdle moves along the column into the lumbar territory during development, although this has not been adequately substantiated. There is, however, a very good example of topographical adjustment of bony structures in the case of the teeth.

To any one occupied with the study of organogenesis, the developmental alteration in topography that is everyAvhere in progress is very striking. In some cases it is obviously a matter of mechanical stress exerted by adjacent organs upon each other, the controlling factors being their relative increase in size and the relative resistance of their tissues; or it may be a matter of traction in connected organs. In other instances we find structures invading new territories by virtue of the direction of their growth, which is dependent on the fact that the proliferation and increase in size of their constituent cells are more active in one direction than in another. In some cases this is associated with a thinning out and disappearance (possibly dedifferentiation) of the opposite pole of the organ, resulting in its complete transposition. Such factors are easily understood and various combinations of them explain most of the instances of developmental topographical alteration in organs which we encounter. There are other cases, however, which are more obscure and in which the movement of the organs or structures during their development cannot be entirely explained by simple mechanical factors; in these the phenomenon resembles a true migration such as is seen in individual cells. For lack of a better explanation, we


MIGRATION — EAR VESICLE IN TADPOLE 117

must consider the possibility of the existence of some force, of the nature of a chemotaxis, interacting between these structures and their environment. It is in this group that we must place the ear vesicle which, during the course of normal development, exhibits a considerable change in position. It is to this that I would call attention here.

From several studies previously reported by the writer (Streeter, '07, '09, '14) and from a recent paper by Ogawa ('21), it is apparent that the determining factors in the posture of the membranous labyrinth involve something more than a passive development of the ear vesicle in the position in which it originally finds itself. It is clearly evident, moreover, that the final position of the labyrinth is not simply the result of an adjustment brought about during its development by the interaction of mechanical processes of the adjacent structures, but that it is due, in part at least, to an autostatic tendency inherent in the vesicle itself, by virtue of which it maintains and accurately adjusts its position during development with reference to the brain and the surrounding structures. When an early ear vesicle is experimentally rotated into an abnormal position, or transplanted in an abnormal position to the opposite side of the same specimen or to another specimen, it subsequently tends to correct its posture, and the final labyrinth, in spite of the previous displacement, is found to possess normal topographical relations.

It is of interest to record that not only under artificial conditions, but also in the ordinary course of development, the ear vesicle of the tadpole undergoes a definite migration, moving from the point of its detachment from the skin to a more median and dorsal location, so that it eventually lies close against the side of the hindbrain with its endoljonphatic appendage overlapping the margin of the thin medullary velum that forms the roof of the fourth ventricle.

If one prepares sections through the auditory region in a series of tadpoles covering the period between the premotile stage and the end of the first month, the changing relations of the ear vesicle to the surrounding structures can be readily made out (figs. 1 to 9). These figures are made with the same


118 GEORGE L. STREETER

magnification and thus, by comparing them, it is possible to determine the actual increase in size, as well as the differentiation of the walls and the alteration in the position of the individual vesicles. In figures 7 and 8 the length of the specimens is given; in the remaining figures the age given is the length of time the specimen was allowed to develop after reaching the operating stage, i.e., when it has acquired a distinct tail bud and gill eminences, but has not yet exhibited any motor response to stimuli.

In the first stage shown (fig. 1) the relatively thin lateral wall of the ear vesicle lies tight against the ectoderm. The vesicle is separated from the thick endoderm and the brain tube by a narrow interval filled with mesenchyme which is beginning to show open spaces in the vicinity of the notochord, elsewhere being relatively compact and heavily laden with yolk. As yet there are no blood-vessels in this region and the acoustic nerve and ganglion are not clearly differentiated from the surrounding tissue. It will be noticed that the lateral plate of the brain tube lies in a vertical plane and the point at which the ventral nerve roots are to converge lies opposite the dorsal tip of the ear vesicle.

In the next stage (fig. 2) the ear vesicle remains in close contact with the ectoderm. The surrounding mesenchyme is assuming a reticular character and in it the primary bloodvessels can be recognized. The acoustic ganglion is distinctly marked off, being attached to the anteromedian surface of the vesicle and connected by a strand with the brain wall. The roof of the latter is thinning out and the lateral walls are undergoing eversion. In the third stage (fig. 3) the conditions are essentially the same, although the vesicle wall has undergone further differentiation, the mesenchyme is distinctly reticular, and there is further eversion of the brain wall. In the sections oral to the one selected for illustration, the acoustic-nerve ganglion is present. It can be seen that the ear vesicle at this time is widely separated from the brain and almost wholly ventral to it. The intervening mesenchyme is loose and would offer slight mechanical obstruction to the migration of the vesicle, and



Figs. 1 to 9 Sections showing the changes in the topographical relations of the ear vesicle of the tadpole during the period between the premotile stage and the end of the first month. In figures 1 to 6 and figure 9 the age given is the length of time the larva was allowed to develop after reaching the operating stage; i.e., tail bud and gill eminences present, but no motor response to stimuli exhibited. X 50. B.V., primitive blood-vessel ple.xus; Endol., endolymphatic appendage; VIII, acoustic nerve ganglion; IX, glossopharyngeal nerve ganglion.


119


120 GEOEGE L. STREETER

certainly the primary brain blood-vessel cannot be regarded as a serious obstruction, since we find that even a much more mature vascular system can readily accommodate itself to any movement of the surrounding organs. A brilliant example of this is seen in the case of the venous drainage of the fetal cerebrum. Migration, however, cannot occur so long as the vesicle adheres to the ectoderm. Its detachment therefrom becomes complete in the next two stages.

The stage illustrated in figure 4 is at the critical point where the vesicle is becoming detached coincident with an invasion of mesenchyme between it and the ectoderm. At the same time the brain shows further development of the roof of the fourth ventricle and continued eversion of its walls which tends to thrust it toward the ear vesicle. The vesicle itself is assuming a more dorsal position, as compared with the previous stage. The portion that is to form the endolymphatic appendage can be clearly recognized from five hours on; by the second day it is not only thicker than the rest of the wall of the vesicle, but also shows a beginning evagination and a distinct differentiation of its component cells. A conception of the shifting that is in progress can be obtained by the realization that the endolymphatic appendage of figure 4 will eventually overlap the rhombic lip of the brain wall.

By the third day (fig. 5) the upper half of the ear vesicle is above the level of the junction of the brain and notochord and is surrounded on all sides by reticular mesenchyme which should favor its migration. Its only attachment is that of the acoustic nerve ganglion which forms a massive strand firmly attached at one end to the brain wall and at the other to the anteromedial wall of the ear vesicle. From the differentiation of the mantle zone -of the brain wall it can be seen that the point of attachment of the nerve corresponds closely to its permanent point of entrance and, tracing it peripherally to the vesicle wall, its fibers can be followed to the macular area. The size and character of the acoustic nerve might lead one to attribute to it a definite influence in any subsequent movement of the vesicle; but we know that the phrenic nerve exhibits no restraining mfluence in


MIGRATION — EAR VESICLE IN TADPOLE 121

the descent of the diaphragm and there is no evidence that the facial nerve exercises any guiding force in the migration of the musculature of the face. It is to be noted that there is still a relatively wide interval between the vesicle and the brain wall. As yet the mesenchyme shows no differentiation into skeletal framework, but on each side of the notochord can be seen the oral extension of the spinal musculature.

Up to the fourth day (fig. 6) there has been a gradual thinning of the main part of the wall of the ear vesicle, accompanied by an increase in the am.ount of the contained otic fluid, and at this time the first steps occur in the formation of the semicircular ducts. A little more than half of the vesicle is now above the level of the junction of the notochord and the brain. The vesicle and brain wall are more closely approximated, which may be explained in part by the further eversion and growth of the latter. On the other hand, there is a beginning differentiation of the subcutaneous tissues and pigment membrane producing an increase in the distance between the ear vesicle and the surface of the larva.

In larvae 9 mm. long (fig. 7) one finds the formation of the semicircular ducts well under way and at the same time the mesenchyme lateral to the ear vesicle is differentiated into a characteristic subcutaneous tissue, while that median to the vesicle shows a condensation into precartilage tissue. Spreading from the chordal area toward the ear vesicle and surrounding the brain can be seen arachnoidal spaces of a primitive type. Notwithstanding this more permanent type of environment, the dorsal migration of the vesicle is not yet complete, for in older stages almost the entire vesicle lies dorsal to the level of the chorda.

In larvae 12 mm. long the endolymphatic appendage and the dorsal crest of the vesicle have nearly reached the level of the rhombic lip, and at the same time the lowest point of the vesicle lies opposite the level of the center of the notochord. The dorsal extension at this time is due in part to the direction of the growth, associated with the formation of the anterior and posterior semicircular ducts and the increase in the length of the endolymphatic appendage.


122


GEORGE L. STREETER


At one month the ear vesicle is completely differentiated into a membranous labyrinth with three semicircular ducts and a characteristic macular area to which is attached the gangHon and its peripheral nerve terminations. A characteristic endolymphatic appendage is present, consisting of a relatively large sac connected by a slender duct with the vestibular portion of the labyrinth. As can be seen in figure 9, the sac now Ues in close contact with the thin roof of the fourth ventricle. The labyrinth lies wholly dorsal to the midlevel of the notochord and is secured in this position by the mesenchymal otic capsule,



Fig. 10 Diagram showing the migration of the ear vesicle relative to the brain wall from the position it occupies at the end of the second*,day (ot.) to the position it attains as a differentiated labyrinth at the end of the first month (of), the brain wall being represented as stationary.

consisting of precartilage tissue, portions of which are already differentiated into typical cartilage cells surrounded by a homogeneous matrix. With this stage the essential relations of the labyrinth may be regarded as established; the subsequent minor changes in its topography are those determined by the mechanical factors of its own further growth and the further growth and differentiation of the surrounding structures.

From the foregoing comparison of the individual stages it is clear that the ear vesicle shifts its position relative to the brain wall to the extent diagrammatically shown in figure 10. ^Miereas at the end of the second day the vesicle lies ventral to and apart


MIGRATION^ — EAR VESICLE IN TADPOLE


123


from the brain, at the end of the first month it is situated close against the lateral brain wall with its endolymphatic appendage overlapping the rhombic Hp. In the figure there has been no account taken of the lateral movement of the brain wall, and therefore to that extent the path of migration of the ear vesicle is exaggerated. Its dorsal migration relative to the notochord, the ectoderm, and the everted brain wall may be represented as in figure 11, which shows more accurately than figure 10 the extent of its change of position relative to the whole environment. Although the normal migration of the ear vesicle is not so marked


D. 5emicirc Lot.



Fig. 11 Superimposed sections of the ear region of a tadpole of the nineteenth hour (dotted) and of another at the end of the first month, enlarged so that the brain is the same size in both cases, the two being fitted so as to exactly coincide.

as that of the thymus and many other organs, nevertheless that phenomenon unquestionably occurs. To some extent the mechanical forces of growth of the concerned parts can be recognized as influencing the migration; no single one of these factors, however, or no combination of them would appear to adequately explain it.

The detachment of the vesicle from the skin is readily explained by the differentiation of the subcutaneous tissues and the formation of the pigment membrane. This begins to take place about the second day. By the fourth day the elements of the pigment membrane make their appearance, and in tadpoles 12 mm. long there is a relatively complete membrane separating the vesicle


124 GEORGE L. STREETER

from the loose tissue underlying the ectoderm. This differentiation releases the vesicle from its firm attachment to the ectoderm, but it does not in any way favor its dorsal migration.

The change in the relative position of the ear vesicle and the brain wall is in part accounted for by the direction of growth of the latter, which undergoes an eversion whereby it is thrust ventralward and lateralward toward the vesicle. The maximum effect of this eversion is reached at the end of the fourth day, but at this time, in addition to the close approximation of the brain wall and the ear vesicle, a dorsal shifting of the latter has occurred relative to the level of the notochord, a fact which can hardly be explained by the change in position of the lateral brain plate.

As to this dorsal migration of the vesicle as a whole, which takes place gradually throughout the first month, one should consider the possibility of its being due to the direction of growth of the vesicle; i, e., that the dorsal portions of the vesicle may perhaps grow more rapidly than the ventral portions. In the case of the endolymphatic appendage, the direction of growth may very well constitute a factor in the attainment of its final position. The dorsal growth of the sac and the elongation of its duct would favor its dorsal shifting. Aside from the slender endoljTiiphatic duct, however, there appears to be nothing to prevent the sac from occasionally going astray orally or caudally, where the tissues would offer httle obstruction to its extension in these directions. That it never does so forces one to postulate the existence of some form of determinative attraction between the endoljiiiphatic sac and the medullar}^ roof to which it later invariably becomes intimately attached.

There is no evidence that the acoustic nerve gangUon plays any considerable part in the way of a guiding or traction force. The nerve can be recognized at the fifth hour, connecting the vesicle with the brain wall, but when it is experimentally detached, as in the transplantation of a vesicle from one tadpole to another, the severing docs not interfere with a correct adjustment of the posture of the vesicle. This corresponds to our experience with other organs, in which the nerves do not act as a check or show


MIGILITION — EAE VESICLE IN TADPOLE 125

any evidence of influencing the migration of the organs in any way. The surrounding mesench>^ne and primitive blood vessels can also be dismissed as factors.

The cartilaginous skull does not make its appearance until the final relations of the labyrinth to its environment are essentially estabhshed, that is, toward the end of the first month, and therefore cannot play a primary part in the migration of the vesicle. However, after the firm otic capsule becomes differentiated the latter must absolutely control those further alterations in the posture of the contained labyrinth which are associated with the final changes in the form of the base of the skull.

LITERATURE CITED

V. Baer, K. E. 1S37 Ueber Entwickelungsgeschicht der Thiere. Konigsberg. FuTAMURA, R. 1906 Ueber die Entwicklung der Facialismuskulatur des Men schen. Anat. Hefte, Bd. 30. Kappers, C. U. Ariens 1910 The migrations of the abducens-nucleus and the

concomitating changes of its root-fibers. Psychiatrische en Neuro logische Bladen.

1910 The migrations of the motor cells of the bulbar trigeminus,

abducens and facialis in the series of vertebrates, and the differences

in the course of their root -fibers. Verh. d. k. Akad. v. Wetenschr. t.

Amsterdam, Tweede sectie, Deel 16. KoHN, A. 1907 Ueber die Schiedenzellen peripherer Ganglionzellen. Anat.

Anz., Bd. 30. KoLLiKER, A. 1861 Entwicklungsgeschichte des Menschen und der hoheren

Thiere. Leipzig. KuNiTOMO, K. 1918 The development and reduction of the tail and of the

caudal end of the spinal cord. Contributions to Embryology, vol. 8.

Carnegie Inst. Wash., Pub. 271. Lewis, W. H. 1901 The development of the arm in man. Am. Jour. Anat.,

vol. 1.

1910 The development of the muscular system. Manual of Human

Embryology (Keibel and Mall), vol. 1. Mall, F. P. 1897 Development of the human coelom. Jour. Morph., vol. 12. Ogawa, C. 1921 ExQeriments on the orientation of the ear vesicle in amphibian

larvae. Jour. Exp. Zool., vol. 32. Rosenberg, E. 1876 Ueber die Entwickelung der Wirbelsaule und das Centrale

carpi des Menschen. Morph. Jahrb., Bd. 1. Streeter, G. L. 1907 Some factors in the development of the amphibian ear

vesicle, and further experiments on equilibration. Jour. Exp. Zool.,

vol. 4.

1908 The nuclei of origin of the cranial nerves in the 10 mm. human

embryo. Anat. Rec, vol. 2, p. 115.


126 GEORGE L. STREETER

Streeter, G. L. 1909 Experimental observations on the development of the

amphibian ear vesicle. Anat. Rec, vol. 3.

1914 Experimental evidence concerning the determination of posture

of the membranous labyrinth in amphibian embryos. Jour. Exp.

Zool., vol. 16. UsKOW, N. 1SS3 Ueber die Entwicklung des Zwerchfells, des Pericardiums

und des Coloms. Arch. f. mikr. Anat., Bd. 22.


>


V


Resumen por los autores, E. L. y E. R. Clark.

El caracter de los linfaticos en el edema experimental.

Los autores han producido edema en el renacuajo mediante: (1) Extirpacion del pronefros; (2) extirpacion del esbozo del corazon; (3) impidiendo el desarrollo de la musculatm-a del coraz6n linfatico, y (4) en conexi6n con la inflamacion aseptica. 1. En los individuos sin pronefros, el liquido plasmatico se acumula tan solo en la cavidad abdominal. La circulaci6n sanguinea se hace mds dificil y el desarrollo de los vasos sanguineos se retarda. Los linfaticos se desarrollan, y en apariencia funcionan normalmente. 2. Cuando se extirpa el corazon el edema esta limitado a las cavidades del cuerpo. Los capilares linfaticos de la cola aparecen un poco mas grandes que lo normal. 3. En renacuajos desprovistos de coraz6n linfatico contractu grandes cantidades de liquido se acumulan en los senos cefalicos, y eventualmente en el tejido subcutaneo del cuerpo y cola. 4. En el edema inflamatorio los copilares linfaticos de la regi6n afectada se distienden.

En embrion^s de polio, los autores impidieron el desarrollo del coraz6n linfatico cortando la cola en los embriones de tres dias. A los siete dias los embriones estan edematosos. La inyecci6n demuestra la presencia de linfaticos distendidos en forma de saco, en vez de aparecer como los conductos mjis pcquefios, presentes en" los embriones normales. Conclusiones :

1. Los capilares linfaticos se desarrollan normalmente, absorbiendo Unfa, sin circulaci6n sanguinea o con circulaci6n defectuosa.

2. Cuando se impide la salida del liquido que ocupa los linfaticos estos se distienden. 3. La acumulaci6n de fluido en los espacios de los tejidos esta asociada con una dilataci6n de los capilares linfdticos. Este resultado se opone a la idea generalmente mantenida por los pat61ogos, de que los capilares linfaticos se contraen en el edema.

Translation by Jos6 F Nonidez Cornell Medical College, New York


The Character Of The Lymphatics In Experimental Edema

ELEANOR LINTON CLARK and ELIOT R. CLARK

Anatomical Laboratory, University of Missouri

FIVE FIGURES

CONTENTS

Introduction 127

Experimental edema in Amphibian larvae 128

1. Removal of the pronephros 128

2. Removal of the blood heart • 129

3. Operation to prevent the development of the lymph-heart musculature 130

4. Inflammatory edema 131

5. Experiments with acetic acid 133

Experimental edema in chick embryos 135

Discussion and conclusion 138

Literature cited 141

INTRODUCTION

Abnormal collections of fluid in the tissue spaces and serous cavities may be caused by a disturbance in any of the factors concerned with the normal formation transudation and absorption of lymph in the animal organism. The causes are probably different in the different tj'-pes of edema and a number of causes may be involved simultaneously (Wells, '18). Although the lymphatic system is known to be intimately concerned with the normal absorption of fluid, the relation of the l^Tnphatics to edema has never been thoroughly studied. It is well known that edema of a limb ma}^ be caused by blocking of the main IjTiiph channels or l\aTiph glands draining the limb, but this type is of relatively rare occurrence in adult warm-blooded animals, owing to the ability of the veins to take over a large share of the absorptive function of the lymphatics.

127

THE ANATOMICAL RECORD, VOL. 21, NO. 2


128 ELEANOR LIXTOX CLARK AN^D ELIOT R. CLARK

Smith and Birmingham ('89) have reported a case of edema of the foetus in which they claim that there was a total absence of lymphatic system.

The reaction of the lymphatic capillaries to the presence of an increased amount of tissue fluid, found in cases of generalized edema of the subcutaneous tissues, is not well understood. According to Adami ('09), the dehcate walls of the l3Tiiphatic capillaries collapse under the increased pressure of the surrounding fluid.

We have attempted to produce edema experimentally by several methods with the particular object of studying the effect of this condition upon the lymphatic capillaries. Tadpoles were used for these experiments, because of the possibility of watching the Ijonph capillaries in the hving, in the transparent fin expansion. Some experiments were also performed upon chick embryos.

EXPERIMENTAL EDEMA IN AMPHIBIAN LARVAE

Two species of frog larvae were used — Rana pipiens and Rana catesbiana. The operations were performed under the binocular microscope, using chloretone anaesthesia. Small glass needles were used for most of the dissections and iridectomy scissors for the removal of the anlage of the blood heart.

The lymphatic vessels of the edematous specimens and of normal larvae of the same ages were injected with India ink. The capillaries of the transparent fins were studied in the hving in the observation chamber previously described (E. R. Clark, '12).

The following methods were tried for producing edema in tadpoles: 1) removal of the pronephros; 2) removal of the anlage of the blood heart; 3) removal of somites to prevent the development of the lymph heart; 4) injection of drops of croton oil to produce inflammation (E. R. and E. L. Clark, '20); 5) acetic acid.

1. Removal of the pronephros

This experiment was performed upon a number of tadpoles, during the spring and summer of 1915. Since the general re


LYMPHATICS IN EXPERIMENTAL EDEMA 129

suits of this operation have been described by Rowland ('16) and Swingle ('19), it is unnecessary to give a detailed description. Edema developed on the day following the operation and was of the type of ascites, fluid collecting only in the abdominal cavity. During the succeeding days, the development of the tadpoles was greatly retarded, the gills remained external for a longer period than in the controls, the coils of the intestine were fewer, the head and eyes smaller, the tail remained much shorter and more pigmented, and the heart beat sluggishly.

]\Iicroscopic observation of the transparent tails of such larvae showed a more sluggish circulation and fewer blood capillaries than in the normal specimens. However, the lymph hearts of the larvae with pronephros removed beat as strongly as did those of the controls, and even more frequently, and the lymphatic vessels of the tail had extended beyond the blood-vessels and were normal in appearance.

2. Removal of the blood heart

The operation for the removal of the heart in tadpoles has been described by Knower ('07) and the effect upon blood-vessels and hanphatics by E. R. Clark ('18). Embryos operated on in this manner soon become edematous — the collection of fluid being confined to the body cavities, the tail remaining small and pigmented.

Although the development of the blood-vessels is greatly retarded with the heart absent, that of the lymphatics is not. The lymph hearts are larger and beat more strongly than do those of normal larvae of the same age and there is an active movement of fluid inside the lymph-vessels as demonstrated by the occasional presence of blood-cells wdthin the lymphatics, W'hich were observed to move along with the current.

In studying the lymphatic capillaries of the tail it was found that these vessels develop normally and often extend beyond the blood capillaries, although in normal embryos of the same age and species, the blood-vessels of this region grow out well in advance of the lymphatics. IMoreover, the haiiphatics are w4der than in normal animals (E. R. Clark, '18).


130 ELEANOR LINTON CLARK AND ELIOT R. CLARK

This experiment showed that lymph continues to pass into the l3Tnphatic capillaries in the absence of the heartbeat and blood circulation and that the growth and absorptive power of IjTuphatics are not dependent upon the blood pressure.

3, Operation to prevent the development of the lymph-heart 7niisculature

For this experiment the somites dorsoposterior to the pronephros were removed on both sides of the larva. In the majority of cases this effectively prevented the development of the pulsating Ijnnph hearts. Such tadpoles developed normally and were practically indistinguishable from the controls for the first four or five days after the operation. On the sixth or seventh day after the operation, edema of the head region of these embryos makes its appearance. This enlargement was noticed invariably on the same day at which the first pulsation of the IjTnph hearts was observed in normal tadpoles of the same age. During the following days the sinuses of the head became still more distended, while those at the sides of the body also enlarged and finally, ten to fourteen days after the operation, the tail became edematous. In contrast to the larvae deprived of their pronephroi or blood hearts, these tadpoles did not contain an excessive amount of fluid in their abdominal cavities.

The tadpoles without beating Ijanph hearts lived for three weeks after the operation — the longest period of survival being twenty-six days. During the first two weeks after the operation the tadpoles were as large as the controls, and practically normal except for the edema. During the last week of life, however, the blood circulation became impaired and often ceased altogether.

In the larvae without lymph hearts, the lymph-vessels were studied by injection of india ink into the main dorsal and ventral lymph-vessels of the tail. The dorsal vessel normally empties into the right lymph heart and the ventral vessel into the left. In the case of the operated tadpoles, the dorsal vessel emptied into a large sinus on the right side and the ventral vessel into a


LYMPHATICS IX EXPEROIEXTAL EDEMA 131

similar sinus on the left side. These tail vessels together with their branches were found to be wider than those of the controls and the pressure inside them was found to be high, as shown by the effort required to fill them with the injection material.

^Microscopic examination of the transparent tails of the tadpoles without l>^nph hearts showed no difference from the normal during the first week after operation. At the end of ten or twelve days the tail begins to show evidences of edema particularly at the base. During the next week these changes become visible throughout the whole tail. The actual increase in the thickness of the tail was measured by means of the micrometer screw of the fine adjustment, b}' focusing on a certain point on the surface of the fin and turning the screw until the opposite surface came into focus, and meanwhile counting the divisions on the screw. The edema is further detected by the changed appearance of the tissue in the fin; the whole region becomes clearer and the connective-tissue cells are more widely separated than in the normal tadpoles. The cells themselves do not enlarge.

Associated with this increase in fluid present in the connectivetissue spaces, we invariably found an enlargement of the Ijniphatic capillaries. The vessels near the base of the tail are first affected and later the more posterior ones enlarge also. Figures 1, 2, and 3 show the difference in size of the hiiiphatic capillaries in these larvae in contrast to that of the blood capillaries of the same specimens and to that of the Ijanph capillaries of normal tadpoles.

In addition to change in cahber, hmphatics of these tadpoles with generalized edema also show changes in contour — the irregular outhne with abundant fine processes characteristic of the normal hntiiph capillary is lost and the endothehum becomes smoother and thinner.

4. Inflammatory edema

The cell reactions which take place after injection of minute globules of croton oil into the tail fins of amphibian larvae, have been described in a recent publication (E. R. and E, L. Clark, '20).


132


ELEANOR LINTON CLARK AND ELIOT R. CLARK


In a number of instances a localized edema was observed at the site of injur^^ The increase in the amount of fluid in the region was easily detected by the increased transparency of the region and by the greater distance between the connective-tissue cells. The increase in the thickness w^as measured by means of the micrometer fine-adjustment screw. The lymphatic capillary sprouts of the edematous region are always wider than similar vessels of neighboring areas; in fact, the simultaneous enlargement of



Fig. 1 A. Drawing of vessels from the ventral fin of a tadpole ten days after operation for removal of the lymph hearts. Lym., lymphatic; B.V., bloodvessel. Thicknessof the tail at this point, 310m. B. Drawing of the same region in the ventral fin of a normal tadpole of the same age. Thickness of the tail, 180 M. Note difference in the size of the lymphatic in the two specimens. B.V., blood-vessel; Lym., lymphatic. X 175.

these capillaries was found to coincide precisely with the increase in intercellular fluid (fig. 15, in article by E. R. and E. L. Clark, The American Journal of Anatomy, ^lay, 1920). This enlargement of the Ijmphatics is characterized by a widening of the lumen of the lymphatics, while the endothelial wall becomes thinner and smoother. These lymphatics regain their normal cali}:)er and contour with a return of the region to its normal thickness. The blood capillaries of such regions show no such chaiiiios.


LYMPHATICS IN EXPERIMENTAL EDEMA 133

•5. Expeviments with acetic acid

These experiments were suggested bj^ the work of IVIartin Fischer ('15) which connects the development of edema with the presence of an acidosis in the tissues. Tadpoles were placed in



Fig. 2 A. Drawing of vessels from the dorsal fin of a tadpole fourteen days after operation for removal of the lymph hearts. Thickness of the tail at this point, 340 M- B. Vessels from the same region of a normal tadpole of the same age. Thickness of the tail, 170 m- This shows still greater enlargement of the IjTnphatic capillary than in figure 1, A. B.V., blood-vessel; Ly7n., Ij'mphatic. X 175.

varying strengths of acetic acid, with the object of producing edematous tadpoles. The. results of these experiments were as follows :

All tadpoles in strengths of acetic acid of 1 to 2000 or stronger were dead at the 6nd of an hour and a half.


134


ELEANOR LINTON CLARK AND ELIOT R. CLARK


Tadpoles left overnight in strengths of acetic acid from 1 to 5000 up to 1 to 15,000 were all dead on the following morning.

Tadpoles in 1 to 20,000 and 1 to 30,000 survived, and at the end of a week they were as large, active and well developed as the controls and showed no signs of edema.

Tadpoles placed in 1 to 18,000 and 1 to 19,000 died within twenty-four hours.



Fig. 3 Drawing of the vessels of the posterior portion of the abdominal wall of an edematous tadpole fifteen days after operation for the removal of the lymph hearts. The lymphatics are greatly distended while the blood-vessels are narrower than normal. X 158.

These experiments were negative in regard to the production of edema in tadpoles by the use of acetic acid in the surrounding fluid, since all specimens died when the acid was stronger than 1 to 20,000, while in this and in weaker strengths of acid no edema developed. Obviously, these results do not necessarily have any bearing whatever on the theory that edema may be caused by acidosis, since the presence of a trace of acid in the surrounding medium may have had no effect on the acidity of the body fluids.


LYMPHATICS IN ^EXPERIMENTAL EDEMA 135

EXPERIMENTAL EDEMA IN CHICK EMBRYOS

We attempted unsuccessfully to produce edematous chick embryos by chemical means— acetic acid was placed in an open dish in the incubator and alcohol also was tried without success. Only one form of edema was produced in chick embryos — that which resulted from the removal of the posterior lymph hearts. The development of the lymph heart is prevented by cutting off the tail rudiment in embryos of two to three days' incubation. This operation and the early development of the lymphatics in such embryos have been described elsewhere (E. R. and E. L. Clark, '19).

It was shown in a former publication (E. L. Clark, '15) that the lymph flow in the early superficial lymphatics of chick embryos is dependent to a considerable extent upon the pulsation of the posterior lymph hearts. It was shown that the commencement of lymph heart pulsations, in chicks of 6| days, is the factor which instigates the lymph flow in the posterior half of the embryo. The area drained by the lymph heart increases until, in embryos of seven to eight days, the direction of the entire superficial lymph flow is posterior through the lymph hearts into the veins of the tail. Associated with the estabUshment of the lymph flow in the superficial lymphatic plexus, channels develop in the exact places where the movement of lymph had been demonstrated in the living chick by the injection of india ink into the superficial lymph capillaries. In addition to the formation of these ducts, the former investigation showed that the lymphatics in later stages enlarge to form sacs at points where two conflicting pressures occur. In this later stage, eight to nine days, the tissue is very loose — so much so, in fact, that it might almost be called edematous, were it not for the fact of its normal occurrence. At this later stage the lymph hearts are chiefly concerned with the flow of lymph from the allantois.

In the former publication a case was described in which an embryo of seven days possessed a stunted tail with a small feebly beating lymph heart. This embryo was edematous and the Ijaiiphatics of the pelvis which drained into the Ijnnph heart were


136


ELEANOR LINTON CLAEK AND ELIOT R. CLARK


large and distended, greatly resembling the sacs normally present in this region in chicks of eight and one-half days.

In the operated tailless chicks of six and one-half days, the stage at which the IjTiiph heart begins to beat in normal chicks, the anterior lymphatics are normal as regards appearance, development of the main duct, and direction of Ijanph flow. The posterior half of the body, however, is markedly edematous in these chicks and the channels normally present over the pelvis



Fig. 4 Drawing of an embryo chick of seven days, in which the tail containing rudiment of the lymph hearts had been removed at the three-daj-- stage. Compare character of the lymphatic plexus, injected with india ink, with that of a normal chick of the same age (fig. 5). The absence of definite channels in the posterior half of the body and the enlargement of the h-mphatic capillaries over the pelvis are particularly noticeable. X 4.67.

are absent and in their place is an irregular plexus of the primitive type, the vessels composing which are much larger than usual. In chicks of seven to seven and one-half days, the stage at which the hmjih flow of the entire superficial hanphatic system is normally influenced by the beating of the l^^nph heart, the chicks were always found to be edematous after the operation for the removal of the lymph heart. The edema is noticeable to the naked eye; it is evident from the greater distance necessary to plunge the injecting cannula before reaching the superficial lymphatics, and also from the greater spaces present between the connective-tissue cells in microscopic sections of such embryos.


LYMPHATICS IN EXPERIMENTAL EDEMA


137


In these chicks, channels over the anterior body wall and pelvis are absent and in their place an irregular plexus is present, many of the vessels of which are greatly enlarged and sac-like in appearance (fig. 4). It is evident from the difficulty encountered in



Fig. 5 Drawing of a normal chick ot six days and twenty-two hours, showing injected superficial lymphatics w^ith newly formed h^mph ducts and Ij-mph heart (L.//.). X 5. (Copied from Clark, E. L., '15, fig. 4.)

injecting these vessels over the pelvis that the fluid in them is under high pressure.

In older stages, that is, in chicks of eight and one-half days and older, the tailless embryos are not noticeably more edematous than normal specimens of the same age. Injections of the superficial l3^llphatics show in most cases that the h^nphatics from the two sides have anastomosed over the stump. Otherwise they


138 ELEANOR LIXTOX CLARK AXD ELIOT R. CLARK

possess the same channels and superficial sacs as the normal specimens. It will be remembered that in normal chicks of eight and one-half days and over, the lymph heart is only shghtly concerned with the h-mph flow in the superficial Ijiiiphatics, being chiefly concerned with the flow of lymph from the aUantois. It is interesting to find in these operated chicks of eight to nine days that the lymphatics of the allantois are so distended as to render them easily visible to the naked eye without injection.

These operations on chicks have added more evidence to that already reported with regard to the importance of the hniph heart in instigating and influencing the early flow" of lymph in the superficial lymphatic plexus and in determining the formation of ducts in the posterior part of the body. They also show that when the IjTnph flow is interfered with in these early stages, by removal of the Ijinph heart, embrj^os become edematous, the development of ducts is interfered with, while the vessels of the superficial l^nnphatic plexus enlarge greatly until they become even larger and more distended than the sacs of older chicks.

DISCUSSION AND CONCLUSION

The ease with which experimental edema is produced in amphibian larvae by any interference in the flow of fluid in the lymphatics is undoubtedly due to the importance of the lymphatic system of the lower vertebrates in connection with the absorption of water. Maxwell ('13) has found that a relatively enormous quantity of water passes through the frog's skin, and ^Moore ('15) has shown that a large part of this absorbed water is carried off by the lymphatics. In the lower vertebrates in which there is an active absorption of water through the skin, lymph hearts which assist in maintaining the flow of lymph are always present. In birds, the two IjTnph hearts, one on each side of the tail, function during embryonic life, but usually atrophj^ at the time of hatching (exceptions to this rule being water birds and the ostrich and cassowary). In the higher vertebrates — mammals and most adult birds, in which the absorption of water through the skin is practically absent — the importance of the lymphatic system as a drainage system is evidently diminished. ^Nlam


LYMPHATICS IN EXPEEIMENTAL EDEMA 139

mals do not possess l>iiiph hearts, but with the appearance of lymph glands the lymphatic system takes on new and important functions not found in lower vertebrates.

The fact that lymph hearts are present in all birds during development, which takes place in a fluid medium, suggests the possibility that there may be an absorption of fluid through the skin of the higher vertebrates during their embryonic life with a resultant increase in absorption of fluid by the lymphatics. In a former paper (E. L. Clark, '15) it was shown that in the chick embryo lymph sacs develop at a stage in which the pressure inside the lymphatic vessels is high, probably owing to increased absorption and the outlet into the veins interfered with, and that such sacs always develop at points where conflicting pressures occur. It is possible that the early development of lymph sacs in mammalian embryos at points where the lymphatic system communicates with the veins may be due to the fact that this actively functioning drainage system has no pulsating lymph heart to assist in the flow of fluid from the tissues.

Moreover, the present experiments, which have shown the important effects upon the absorption of fluid from the tissues resulting from an interference with the drainage of fluid by the lymphatics, in tadpoles and in chick embryos, suggest the possibility that edema of the human embryo may also be caused by a blockage of the main l3rmph channels, especially of the thoracic duct.i

1 Smith and Birmingham ('89) assert that in the edematous foetus which they studied the lymphatic system was entirely absent. However, the illustration which they give (a low-power drawing of a microscopic section) contains certain structures which are unquestionably lymphatics, and not 'spaces' as they are labeled. Microscopic studies of edematous tissues (Marchand, '11; E. R. Clark, '16, and this article) have shown that fluid in subcutaneous tissues does not collect in 'lakelets,' but that it is evenly distributed, separating the cells in a uniform manner. The more probable explanation for this interesting case would appear to be that instead of being absent, the lymphatic system was blocked at some important point — perhaps at the outlet of the thoracic duct — and that there had then occurred a generalized edema of the embryo and a simultaneous distention of the lymphatics including the finest capillaries. It is interesting to see that in this case the 'spaces' in the mesenchyme are much larger than the blood capillaries.


140 ELEANOR LIXTOX CLARK AND ELIOT R. CLARK

The experiments reported here have yielded the following results in regard to the relation of the l^^nphatics to experimental edema :

With the removal of the pronephros or the blood heart in amphibian larvae and the consequent abnormal collection of fluid in the serous cavities, the lymphatics continue to develop and to function in a normal manner. Their development and function are not interfered with even by the absence of circulation in the blood vascular system.

Generalized edema of the embryo may readily be produced by mechanical interference with the outflow of fluid from the lymphatics (removal of the lymph hearts in tadpoles and in chick embryos).

In such cases of generahzed edema the l>Tnphatics invariably enlarge and the delicate lymph capillaries do not collapse with the increased pressure outside the vessels, but, on the contrary, they continue to absorb fluid until they become greatly distended.

In cases of localized edema, in areas where an inflammation has b.een produced, the lymphatic capillaries of the edematous region respond to an increase in the fluid outside by enlarging at the tips, and they resume their normal size with the disappearance of the edema.


LYMPHATICS IN EXPERIMENTAL EDEMA 141

LITERATURE CITED

Adami, J. G. 1909 The principles of pathology, vol. 2, chap. 5, p. 103. Lea & Febiger.

Clark, E. L. 1915 Observations of the Ijinph-flow and the associated morphological changes in the early superficial lymphatics of chick embryos. Am. Jour. Anat., vol. IS, p. 399.

Clark, E. R. 1916 A study of the mesenchyme cells in the tadpole's tail toward injected oil globules. Anat. Rec, vol. 2, no. 1, p. 1. 1918 Studies on the growth of blood-vessels in the tail of the frog larva — by observation and experiment on the living animal. Am. Jour. Anat., vol. 23, no. 1, p. 37.

Clark and Clark 1920 The character of the lymphatics in experimental edema. Proc. Amer. Assoc, of Anatomists, Anat. Rec, vol. 18, no. 3, p. 227.

Fischer, ISI. 1915 Oedema and nephritis. John Wiley's Sons, New York.

HowLAND, R. B. 1916 On the effect of removal of the pronephros of the amphibian embryo. Proc. Nat. Acad, of Sciences, vol. 2, p. 231.

Knower, H. McE. 1907 Effects of early removal of the heart and arrest of the circulation on the development of frog embryos. Anat. Rec, no. 7; Am. Jour. Anat., vol. 7, no. 3, p. 161.

Luckhart 1910 Contributions to the physiology of lymph. Comparative electrical conductivity of lymph and serum of the same animal and its bearing on theories of Ijonph formation. Amer. Jour, of Physiol., vol. 25, p. 345.

McClure, C. F. W. 1919 On the experimental production of edema in larval and adult Anura. Jour, of General Physiol., vol. 1, no. 3, p. 261.

Marchand, F. 1911 Das Oedem im Lichte der Kolloid-Chemie. Centr. f. allg. Pathol., Bd. 22, S. 625.

Maxwell 1913 On the absorption of water by the skin of the frog. Amer. Jour, of Physiol., vol. 32, p. 286.

Moore, A. R. 1915 On analysis of experimental edema in frogs. Amer. Jour, of Physiol., vol. 37, p. 228.

Smith and Birmingham 1889 Absent thoracic duct causing oedema of a foetus. Jour, of Anat. and Physiol., vol. 23, p. 532.

Starling, E. H. 1898 The production and absorption of lymph. Text-book of Physiol. E. A. Shafer. Edinburgh. MacMillan.

Swingle, W. W. 1919 On the experimental production of edema by nephrectomy. Proc. Amer. Assoc, of Anatomists, Anat. Rec, vol. 16, p. 165; Journ. of Gen. Physiol., vol. 1, no. 5, p. 509.

Wells, H. Gideon 1918 Chemical pathology, chap. 12. W. B. Saunders Co.


Resumen por el autor, S. E. Whitnall.


Algunos miisculos anormales de la 6rbita.

El autor describe un musculo elevador de los parpados superior que presenta dos anomalias comunes de los fasciculos que pasan : (a) A la polea del musculo oblicuo superior (musculo tensor de la troclea, de Budge), y (b) A la glandula lacrimal; y en adici6n, (c) existe una banda transversa y entrecruzada parcialmente (musculo orbitario transverso). El origen del musculo oblicuo inferior del globo ocular fue examinado en cien 6rbitas, hallando el autor un desplazamiento lateral de su posici6n descrita como normal, (inmediatamente adyacente al borde de la incisura lacrimal u orificio superior del canal naso-lacrimal) en muchos casos, y en el 14 por ciento de los casos estaba separado un cuarto de pulgada, proximamente. En un caso, cuando la distancia era 7 mm. la inserci6n ocular fue examinada, hallando el autor que estaba situada mas arriba de lo normal. Otras anormalidades observadas son las de los musculos rectos, mencionadas en la literatura, junto con ejemplos de conexiones entre los musculos, encontradas por el autor en una serie de disecciones.

Translation by Jos6 F. Nonidez Cornell Medical College, New York


AUTHOR S ABSTRACT OF THIS PAPER ISSUED BY THE BIBLTOGRAPHIC SERVICE, MAT 9


SO^^IE ABNORMAL MUSCLES OF THE ORBIT

S. E. WHITNALL

Dcj)artment of Anatomy, McGill University

TWO FIGURES

The following instances of abnormal muscles were met within a series of dissections of the orbit.

LEVATOR PALPEBRAE SUPERIORIS

There are three variations from the normal in this instance which was found in the left orbit of an adult female cadaver, of which the other orbit was not available for dissection.

1. The most striking feature is the presence of a band of muscle fibers, 2 imii. broad, passing transversely across the anterior part of the orbit and interwoven to a certain extent with the fibers of the levator palpebrae superioris. The extremities of the band curve shghtly backward to be attached to the periosteum of the medial and lateral walls at about the junction of their anterior and middle thirds.

2. From the medial margin of the levator itself a well-defined slip is separated off and passes in the direction of the trochlea or pulley of the tendon of the superior oblique muscle. This slip loses its fleshy character before it reaches the trochlea, being continued on by connective-tissue strands.

3. From the lateral margin of the levator a well-marked offshoot passes both to the orbital wall and also to the lacrimal gland. In two other cases I have seen similar fasciculi passing to the lacrimal gland. They are attached to the connective tissue which forms the so-called capsule at the posteromedial region of the gland, and traction upon the levator draws the gland slightly backward. Alicroscopical examination showed all these fibers to be cross-striped.

14.1

THE ANATOMICAL RECORD, VOL. 21, NO. 2


144


S. E. WHITNALL


There have been described two abnormalities of the levator of the upper eyelid :

a. Where the muscle presents an offshoot from its medial border which passes to the pulley of the superior oblique muscle, replacing or reinforcing the normal fascial expansion of its sheath to that point. This muscular slip is the tensor twchleae of Budge ('59), and is identical, according to Macahster, with muscles described by Vesalius, Molinetti, Kolmus, Sandifort, and with



Fig. 1 Left orbit dissected from above to show an abnormal levator j)alpebrae superioris, showing T., a transversus orbitis; B., a gracillimus or tensor trochlear or comes obliqui superioris, as it is variously termed; G., a slip passing to the lacrimal gland; S.O., is the superior oblique muscle.

the co77ies oblique superioris of Albinus, and gracillimus orbitis of Bochdalek ('68). According to Budge, it is found in 10 per cent of cases, but in the writer's experience is much more rarely found in a well-defined state. In one preparation there were present two long muscle bundles, arising in common with the levator and ending anteriorly, one upon the fascia bulbi between the superior oblique and the globe, the other on the orbital margin beneath the pulley; the nerve supply came from the fourth nerve; the superior oblique was broader than usual. Ledouble


SOME ABNORMAL MUSCLES OF THE ORBIT 145

has found supernumerary fasciculi accompanying the reflected tendon of the superior oblique, and has further recorded a case where the direct or fleshy part of this muscle was absent, the reflected or normally tendinous part being muscular and arising from the site of the pulley, recalling the type found in non-mammalian vertebrates.

b. The musculus transversus orhitis, described by Bochdalek in 1868 as a muscle passing from the anterior and upper part of the OS planum of the ethmoidal bone across the upper part of the orbit to its, lateral wall. It consists at its origin of small tendinous bands enlarging to fleshy bundles which give off various attachments to neighboring fascia and especially to the levator palpebrae superioris with which it is closely connected; in fact, when the transversus orbitis is small it practically forms part of the levator. Macahster and Ledouble consider it as being a backwardly displaced shp of the orbicularis palpebrarum. This transversus orbitis is sometimes confused with the graciUimus, as, for example, by Howe ('07).

Perna ('05) described an 'abnormal transverse muscle' of the orbital cavity in man, which appears to be a transversus orbitis. He differs from Macalister as to the real origin of the muscle, considering it to represent the remains of the primitive muscular membrane which surrounds the organ of vision in lower vertebrates and which persists longest in phylogeny where the bony orbit is least complete and of least protection; he considers the levator itself to have the same origin, differentiated later for the special function of palpebral movement. An objection to this view is that the oibital periosteum, the periorbita, with its vestige of involuntary musculature found in the infra-orbital fissure in man and much more largely developed in certain lower animals, may be considered on sounder morphological grounds to be the representative of this primitive orbital cavity (jNIotais, '87; Groyer, '03). It may also be pointed out that the frontal nerve is lying between the planes represented by these two structures — the levator and the periorbita.

Neither would this anomaly appear to be derived from the peribulbar involuntary musculature described by Landstrom


146 S. E. WHITXALL

('07) and recently re-investigated by Hesser ('13), since the fibers are of a different nature and lie on a much more superficial plane.

As regards the view of .Alacalister that the abnormality is formed by a portion of the orbicularis oculi, it is difficult to see how a portion of the superficial facial muscle sheet comes to be displaced to so deep a plane, posterior to the tarsal plates and septum orbitale, the latter of which is generally regarded as forming the anterior boundary of the orbital cavity, and why such fasciculi are so intimately connected with the levator.

A third explanation which might be considered is that the transversely disposed muscle fibers replace that thickened part of the superficial fascial sheath of the levator which runs in the same direction across the orbit and presents somewhat similar attachments and, it has been suggested, may act as a check ligament to the action of the muscle ('WTiitnall, '10). This view is supported by the fact that in the present instance the fascial sheath was but little developed and formed no transverse band such as is normally present. The difficulty here is to reconcile the fact that while it is not uncommon to find the reappearance of muscle fibers in connective tissue which has replaced muscle, as, for example, in the case of the panniculus carnosus, yet preexisting connective tissue tends under strain rather to become condensed and developed into a definite ligament than to be replaced by muscle, as instanced by the appearance of definite ligaments in certain portions of the capsules of joints. On these grounds Perna's view is borne out by the numerous offshoots of the levator which may appear — it may be the remains of a much larger muscular sheet, but it is not homologous with the primitive membranous orbit as represented by the periorbita.

The present instance of an abnormal levator palpebrae superioris muscle is of interest in that it shows, though ])erhaps feebly developed, the two variations commonly described, the tensor trochlea and the transversus orbitis, and in addition an offshoot passing to the lacrimal gland. The latter could have a much more effective action as a retractor glandulae lacrimalis than the medial offshoots as a tensor trochleae, since the gland is fairly movable, the trochlea only slightly so.


SOME ABNORMAL MUSCLES OF THE ORBIT 147

MUSCULUS OBLIQUUS INFERIOR

The inferior oblique muscle of the eyeball is stated to arise from the anteromedial part of the floor of the orbit, just within the margin and immediately adjacent to the opening of the nasolacrimal canal (incisura lacrimalis). The site may be marked by a small oval impression and often the margin of the orbit is slightly lipped in this region. So close is the origin to the edge of the canal that occasionally fibers of the muscle are found to spring from the periosteal covering (lacrimal fascia) of the lacrimal sac at its base (fig. 2).

Since several cases were found by the writer where the origin was displaced laterally some distance from this normal site, it appeared worth while examining a series of orbits. Out of 100 orbits dissected the distance of the origin from the edge of the nasolacrimal canal was as follows:

Adjacent (0 to 1 mm. away) in 45 cases

2 mm. distant in 14 cases

3 mm. distant in 19 cases

4 mm. distant in 8 cases

5 mm. distant in 6 cases

6 mm. distant in 4 cases

7 mm. distant in 4 cases

Total 100

Approximately, therefore, the origin lay a quarter of an inch (5 to 7 mm.) lateral to the normal site in 14 per cent, the displacement was more commonl}^ found in left orbits.

In both orbits of one subject (female) the origin of the muscle was found situated 7 mm. away from the orifice of the canal, and the insertion of the muscle onto the right eyeball was specially examined (fig. 3). The breadth of the insertion was 8 mm. (usually 9.9 mm.) and was placed above, instead of below, the horizontal meridian ; its nearest point was 5 mm. from the optic nerve — a httle less than usual; its central point was 9 mm. (usually 11 mm.) distant from a corresponding point on the line of insertion of the superior obhque muscle. The total length of the muscle was 37 mm., which appears normal. In two other cases


148


S. E. WHITNALL


of similar origins examined the most marked differences of insertion were again in a higher position on the eyeball, though it should be added that, according to Howe, the ocular insertions of the inferior oblique are more variable than any of the other muscles. The length of the muscles was normal.

As regards the possible effect of such a laterally displaced origin on the action of the muscle, it is first to be noted that, since



Fig. 2 Diagram to show normal position of origin of the inferior oblique muscle and its insertion onto the eyeball.

the attachment is behind the equator of the globe, contraction of the muscle will tend to draw the latter forward, and the more directly the origin is situated in front of the eyeball, at a greater advantage can the muscle so act. In the second place, the effect of the displacement is to bring the origin nearer the insertion, and so the length of the muscle would be decreased. Since the length of a muscle, in which the fibers are arranged parallel to the long axis, is one of the factors which determine the extent


SOME ABNORMAL MUSCLES OF THE ORBIT 149

of movement of its insertion, this shortening would tend to influence the range of action. In these cases, however, the disadvantageous position of the origin is compensated by the higher position of the insertion on the globe and the length of the muscle is not affected. The independent action of the normal inferior oblique is to elevate and abduct the cornea and cause the globe to revolve outward on its anteroposterior axis. The first and las<"


Fig. 3 Diagram to show an instance of abnormal origin of the inferior oblique muscle and its higher attachment onto the eyeball.

of these movements are not impaired by the higher position of the insertion; abduction is chiefly effected by the lateral rectus, though shared by the superior rectus, so that the effect on this movement is negligible.

The superior oblique muscles were examined in the same subjects, especially as in the first case the pulley for the muscle was situated further forward than usual, being almost on the orbital margin (though the position w^as normal in the other cases exam


150 S. E. WTIITXALL

ined). Here the angle between the belly of the muscle and its reflected tendon was apparently less than usual, but accurate measurement was impossible, owing to the nobility of the globe in the advanced stage of the dissection. The angle was certainly much less than the normal 54°, and appeared about 31°. The insertion onto the globe in each of two cases was broader than usual (14 mm. and 11 mm., instead of an average width of 9.5 mm.), but the position as regards the vertical meridian was normal and not of the myopic type (i. e., parallel to and wholly on the lateral side of the meridian) ; as in the case of the inferior obUque, however, there is much variation in the 'normal' insertion.

From comparative anatomy it is seen that this condition resembles that found in certain fishes, w^here the obhque muscles arise from the orbital margin more anteriorh', in front of the globe.

RECTI MUSCLES

As regards abnormahties of the recti muscles, it is probable, to judge from the writer's individual experience in finding quite a number of gross anomaUes in a series of dissections, that such are by no means as excessively rare as would appear from the number recorded in the Uterature; in the ordinary dissectingroom conditions do not favor their identification, and in life some may be unrecognizable through compensatory action of the other muscles. They can of course be explained by errors in development by cleavage from the common premuscular mesoblastic mass. In the following notes, mention will be made of such abnormahties as have been recorded in addition to those found by the writer.

The superior rectus has been found to give off a muscular slip 15 mm. long, which arose from the same origin from the annulus of Zinn and passed do^^•nward and forward across the lateral face of the optic nerve to join the inferior rectus about its midpoint; the nerve supply came from the inferior division of the third nerve (Aubaret, '09).

The medial rectus has been found absent in some cases of divergent strabismus (Ledouble, '97; Krause). Its posterior third


SOME ABNORMAL MUSCLES OF THE ORBIT 151

may be fused with the inferior rectus. A bifid sclerotic insertion by two tendons, 16 mm. in length, is recorded (Wicherkiewicz, '07).

The lateral rectus has hkewise been found undeveloped in some cases of convergent strabismus (Ledouble, Krause), and a case of atrophy of the muscle has been noted on operating for strabismus in the hving (Bourgeois). A fasciculus may pass from it to the inferior rectus, as is normal in certain ruminants, or to the lateral wall of the orbit (Aloseley, '53). A lateral rectus with two extra fasciculi which passed forward to end on the inferior tarsal plate and lateral wall is recorded (Curnow, '73). In a specimen dissected by the writer there was a well-marked, fleshy bundle 7 mm. long and 2 mm. in diameter, passing from the lateral rectus across the posterior third of the orbit beneath the optic nerve to fuse with the belly of the medial rectus; no nerve could be traced to it.

The inferior rectus has been found by the writer to give off a large muscular bundle which passed lateral to the optic nerve and joined the superior rectus; it was innervated by the lower division of the third nerve.

An abnormal muscle bundle (musculus ohliquus accessorius inferior) has been found by Rex ('87) passing from the apex of the orbit to the inferior obhque, but also sending a slip to join the inferior rectus; it was found in both orbits, and was supphed by the third nerve.

As regards the vestiges of the musculus retractor bulbi which have been found in man, the reader should refer to an article by the writer ('11); to the hterature therein cited may be added a paper by Hopkins ('16).


152 S. E. WHITNALL


BIBLIOGRAPHY


AuBARET 1909 Sur une anomalie extremement rare des muscles droits de I'oeil.

Faisceau miisculaire anastomotique reliant le droit superieur au droit

inferieur. Socicte d'Anatomie de Bordeaux, Seance du 19 juillet. BocHDALEK 1868 Beitrag zu der anomalen Muskeln der Augenhohle. Prager

Vierteljahrsschrift, Bd. 4. Budge 1859 Beschreibung eines neuen Muskels, etc. Zeitschrift fiir Ration elle Medizin, 3, vii, S. 273. CuRNOW 1873 Notes of some irregularities in muscles and nerves. Journal of

Anatomy and Physiology, vol. 7, p. 304. Groyer 1903 Zur vcrgleichenden Anatomie des Musculus orbitalis und der

Musculi palpebrales (tarsales). SitzungsberJcht d. k. Akad. d. Wissen schaften in Wien, Bd. 112, iii, S. 50.

1905 Zur Anatomie des Muse, palbebral. sup. des Menschen. Zeitschrift fur Augenkheilkunde, Bd. 14, S. 365.

1906 Ueber den Zuzammenhang der Musculi tarsales (palpebrales) mit den geraden Augenmuskeln, etc. Internat. Monatschrift fiir Anatomie und Physiologie, Bd. 23, S. 210.

Hesser 1913 Der Bindegewebsapparat und die glatte Muskulatur der Orbita

beim Menschen im normalen Zustande. Anatomische Hefte (Merkel

und Bonnet), Bd. 49, S. 181. Hopkins 1916 The innervation of the muscle retractor oculi. Anat. Rec.,

ii, vol. 5, p. 199. Howe 1907 The muscles of the eye. Putnam, New York. Landstrom 1908 Ueber Morbus Basedowii. Nord. Med. Ark., Stockholm.

(Abstract in Nagel's Jahresbericht fiir Ophthalmologie, 1907, p. 472.) Ledouble 1897 Traite des varietes du systememusculaire de I'homme. Paris. Macalister 1875 Additional observations on muscle anomalies in human anatomy. 3rd series (Orbit), Transactions of Royal Irish Academy, vol.

25, p. 7. MosELEY 1853 On an additional muscle of the eye. Monthly Journal of the

Medical Sciences, vol. 17, p. 531. MoTAis 1887 L'appareil moteur de I'oeil. Paris. Perna 1905 Un musculo trasverso anomalo della cavita orbitaria neiruomo.

Anatomischer Anzeiger, Verhandlung, Bd. 20, S. 215. Rex 1887 Ueber einen abnormen Augenmuskel (]\Iusculus obliquus acces sorius inferior). Anatomischer Anzeiger, ii, Bd. 20, S. 625. Whitnall 1910 On a ligament acting as a check to the action of the palpebrae

superioris muscle. Journal of Anatomy and Physiology, vol. 45, p. 131.

1911 An instance of the retractor bulbi muscle in man. Journal of

Anatomy and Physiology, vol. 46, p. 36.


'i"


Resumen por el autor, H. E. Radasch.

La determinacion del tanto por ciento de substancia organica en el hueso.

El tanto por ciento de substancia organcia en el hueso compacto es 32 a 33 por ciento, segiin los autores. De la inspecci6n de la literatura general no se desprende el metodo empleado en la determinacion de dicha substancia organica. Con el objeto de determinar el tanto por ciento real y hallar, a ser posible, el metodo empleado por los primeros observadores, el autor ha llevado a cabo varios experimentos de diversa naturaleza. Despues de preparar cuidadosamente trozos del femur, tibia y fibula, peso una serie de trozos, que se calcinaron despues, pesando el producto de esta operacion. La perdida de peso indica la cantidad de substancia organica incinerable que forma parte del hueso compacto.

Entre los veinte a sesenta aiios de edad, el tanto por ciento medio hallado es 40.75. En el gato adulto el tanto por ciento de peso en del hueso joven es 38.32, mientras que en el conejo (dos tercios del crecimiento total) el tanto por ciento medio es 38.90. Mediante otros metodos, la humedad y las substancias solubles en el alcohol y el eter fueron eliminadas, fijando la cantidad de contenido organico fijo. La cantidad media de humedad durante el periodo comprendido entre los veinte y sesenta afios es 8.42%, y la relacion 7 de la substancia organica fija y el hueso seco es solamente 34.92%. La cantidad media de substancia soluble en el eter es 9.27 por ciento; la relaci6n media de la substancia organica fija y el hueso extractable es 3L34%. Parece sin embargo que el peso tipo debe ser el del hueso j6ven, y si se acepta esto, la cantidad media, de substancia organica contenida en el es 40.75 por ciento.

Translation by J036 F. Xonidcz Cornell Medical College, New York


AUTHOR S ABSTRACT OF THIS PAPER ISSUED BY THE BIBLIOGRAPHIC SERVICE, MAT 9


THE deter:viixatiox of the percentage of the

ORGANIC CONTENT OF CO^^IPACT BONE

H. E. RADASCH

Laboratories of the Daniel Baiigh Institute of Anatomy of the Jefferson Medical

College

In considering the chemical composition of bone we are told that it consists of two main substances intimately commingled, viz., earthy and animal substances. The former comprises the following substances, according to Cunningham's Anatomy ('14):

per cent

Calcium phosphate 53 .23

Calcium carbonate 7 .32

Calcium fluoride 1 .41

Magnesium phosphate 1 .32

Sodium chlorid . 69

68.97 Organic material 31.03


100.00


The organic substances comprise fats and ossein.

According to Piersol, who quotes Berzelius, the inorganic material comprises 67.3 per cent, while the organic material consisting of gelatin and blood-vessels constitutes 33.3 per cent. Schaefer, Prudden (Ref. Handbook of Medical Sciences), Sobotta, all give the same as Piersol, apparently having accepted the same source as their guide. Gra^^'s Anatomy ('18) gives the organic content as from 67 to 68 per cent and so the inorganic constitutes 33 to 32 per cent.

We are further told by Schaefer that the animal material, improperly called cartilage of bone, differs from cartilage phj'sically and chemically. It is much more flexible and softer and upon boiling the bone yields mainly gelatin. He concludes that

153


154 H. E. RADASCH

the animal material closely resembles white fibrous and areolar tissues in that it consists mainly of collagen.

Normal bone is hard, rigid (to a certain extent), tenacious, and also elastic. The earthy materials contribute to its hardness and rigidity, while the organic material gives bone its tenacity and elasticity. With the last characters in mind, we can readily understand some of the results of fractures. Although we are not told so, we naturally conclude that the foregoing percentages and characteristics apply to compact bone and to the adult type. This being agreed, we naturally would consider that the bones of the young and adolescent would contain a greater percentage of organic material and, therefore, a lower percentage of inorganic substance. This chemical difference, therefore, makes a physical difference to the effect that the bones of the young should, theoretically, be more elastic and tend less to fracture under the same proportionate strain than that of the adult; that the writer beUeves the surgeon will admit. In the case of ultimate fracture, however, we might expect a different result than in the adult, and consequently we find the green-stick fracture pertains to youth entirely and does not occur in the adult. This is due to the higher percentage of organic substance in the bones of the young. This will be shown actually in the succeeding data.

We are told that by subjecting the bone to an open fire (calcining) the organic substance is burned out, leaving a white, brittle, chalk-Uke substance that preserves its original shape, but with the loss of about one-third of its weight. This porous cast is easily broken, so apparently the substance which gives tenacity has been removed. We might naturally infer from this that in old age there is a reduction of organic substance, for it is known that in old individuals fractures occur more easily than in those in the prime of hfe; also repair is less rapid and less satisfactory in old age. We would believe, then, in the elderly, that there is a reduction of organic substance that causes the bone to yield more quickly to strains. Yet Rusby (Ref. Handbook of the ^Medical Sciences) tells us that as age advances there is a diminution in the mineral constituent of bone and the


ORGANIC CONTENT OF COMPACT BONE 155

organic element is slightly increased. This should make the bone somewhat more tenacious and less prone to fracture — just the reverse of actual experience. He states that this increase is due to the replacement of bone by enlarged blood-vessels and marrow, so that there is, in reaUty, a reduction of fixed organic material. Yet in those bones examined in this work no reduction was noted, but rather an increase, so that theoretically the bone should not be weakened in old age as it naturally is. There is apparently a thinning or diminution of the actual bony layer of the long bone, and this accounts partly for the readiness of the fracture.

Hoppe-Sejder is quoted (Ref. Handbook of the Medical Sciences) as giving the following composition of dried bone without the removal of the marrow or blood. Water, 50 per cent; fat, 15.75 per cent; ossein, 12.40 per cent; bone earths, 21.85 per cent. Wliy the bone-marrow^ and blood should be considered and included in the determination of the organic composition of bone seems strange. These two substances are not a direct part of the bone and they should be got rid of entirely in the determination of the organic constituency. Again, these substances will give some ash and will contain some elements that are concerned in bone formation, so that the effect of calcination of fresh bone with its blood and marrow would be to add to the inorganic constituents the amount of ash of the organic parts. As a result, the percentage of inorganic would be somewhat higher than it should.

For the same reason there is no way in which the organic structure of cancellous bone can be determined, as the marrow contained cannot be got rid of in any waj^ that would not tend to remove some of the soluble organic constituent of the bone. The percentage of organic material would be quite high in such a case.

It would seem that to get the real percentage of organic substance of compact bone, it would be necessary to remove as thoroughly as possible all traces of fat, marrow, and bloodvessels and external, or surface moisture. In that waj- the organic material remaining would practically belong to the bone and be a part thereof.


Primarily, the reason for the following determination was to find out, if possible, a definite relation, or variation, of the organic constituents of bone at the various ages. Just what methods of procedure were used by those who made the early determinations was not known, so some fresh bone was cleaned, weighed, calcined, and the contents determined. By this method the percentage of inherent, fixed, or component organic substance was so far above that given in the text-books that it caused surprise. There was no reason to believe that it could be an accidental variation, so that the writer immediately wondered how Berzelius, et al., made their determinations. If, according to Hoppe-Seyler, the marrow and blood-vessels were included with the bone, then we can see readily that there would be a variation, but this would make the organic content still higher than the author's determination.

In order to attempt to find out the method used by the older chemists, the determination of the organic content was carried on in a number of different ways.

So as to try to reach as near as possible the true percentage of organic substance in compact bone, five different sets of determinations were carried out. Four of these were applied to every sample of green bone and the fifth applied to the bones used for study by the students. The determinations were made on the bones of adults, varying the ages as much as possible, and stillbirths and even fetuses. In addition, in order to have a comparative anatomy relationship, determinations were also made in rabbits and cats.

The same method of preparation was used in all, except the bones used by the students for study. Certain bones only were used in all ages and in all of the animals, viz., femur, tibia, and fibula. In order to get as fair a sample of compact bone, i.e., where it would be most compact, the middle (from end to end) of each was chosen, and a section cut out and handled in a certain routine manner in all instances. The material was chosen chiefly from postriiortem subjects, and not from the remains of the subjects from the dissecting-room for several reasons: 1) To avoid involving thie chemicals of the embalming fluid. 2) In


ORGANIC CONTENT OF COMPACT BONE 157

order to determine the normal inherent moisture of the bone as just removed from the body. Determinations were also made in bodies that had been refrigerated for some time, and a difference was noted in the results here also.

After removal of a section of the femur, tibia, and fibula from the same sources, the flesh was allowed to remain on the others until one had been prepared for all four methods, as follows: First, the flesh of one piece of bone is all carefully cleaned off and the periosteum completely stripped, say off the femur. This caused no trouble except along the Unea aspera of the femur and at all of the borders of the tibia and the fibula. Here the membrane adheres most tenaciously, as many processes extend into the bones at these lines and serve to anchor the membrane firmly in position. Here care must be exercised to get out all traces of Sharpey's fibers, else they might naturally add their mite to the organic constituent of compact bone, and erroneously so.

The next step is to strip out all of the marrow and then cut out all of the cancellous spicules along the inner surface of the bones. In cutting these away considerable fatty matter is thus exposed and removed, thereby getting rid of another errorproducing element. ^^Tien as much of this cancellous bone as possible has been removed, one can feel reasonably sure that the remainder is a real sample of compact bone. Then the bone is carefully wiped externally and internally and a section (ring) about 1 cm. in height is cut; this is then cut into quarters. Each quarter is then carefully wiped again, especially the narrowcavity side, in order to remove all superficial moisture and fat; it is then weighed and this is the green weight. This is done with all four pieces, so that this green weight serves as an excellent check in the three other determinations.

Next the tibia is treated in the same way and then the fibula. The reason why all are not cleaned at once and then cut and weighed is because, if cleaned and left exposed to the room air, some of the moisture would escape and cause a variation in the determination. For that reason each specimen is treated in this routine manner. This may seem far-fetched, but it is of

THE ANATOMICAL RECORD, VOL. 21, NO. 2


158 H. E. RADASCH

the greatest importance, especially in the handling of fetal bones and bones of the child at birth. Here the parts must be cleaned, wiped, and weighed as rapidly as possible, or there is a marked variation, as these young bones have a greater percentage of inherent moisture. If the weighing process is slow, this variation will be noticed right on the balance pans.

By this method pieces of adult bone weighing from 1.1 grams up to over 3 grams were prepared. In fetal bones and those of the cat and rabbit, however, the weight of green bone was about 0.5 gram, as they are very bulky for their weight.

To procure and prepare four pieces of femur, tibia, and fibula and get the green weight of each requires about two hours of tedious and patient labor, but this is not the end.

The importance of the removal of all of the cancellous tissue and contained marrow will be shown in determinations A, B, C, and D. It will also show why cancellous bone proper should not be used, as the true organic constituency of osseous tissue cannot be correctly determined therefrom. This is due to the inability to get at and to remove the marrow from the canceUi.

Each of the four pieces of sample was treated as follows:

1. Green. The first piece of each bone was immediately calcined until the weight was constant and then the percentage of organic material determined, as will be shown later.

2. Oven-dried. The second piece of each bone after preliminary weighing was placed in an oven at 56°C. for twenty-four to forty-eight hours, allowed to cool, and then weighed. The loss in weight indicated the amount of moisture and the volatile organic substance present. It was then calcined until the weight was constant. By this method the percentage of moisture and volatile matter was found and also the amount of what might be termed real, or fixed organic material was obtained. In addition the green (original) weight permitted a determination of the organic material in green bone before the drying process was undertaken, giving a green-check determination.

3. Alcoholic-extracted and oven-dried. The third piece of each bone (after preliminary weighing) was placed in a 95 per cent


ORGANIC CONTENT OF COMPACT BONE 159

alcohol for twenty-four to forty-eight hours and then transferred to an oven at 56°C. for twenty-four to forty-eight hours, and then weighed when cooled. The weight lost indicated the moisture and volatile material and alcohol-soluble material. After calcining then the percentage of organic material in green bone, the percentage of moisture, volatile material and alcohol substance was next determined, and lastly the amount of remaining (fixed) organic substance.

4. Ether-extracted and oven-dried. In this determination a fresh piece from each bone (after preliminary weighing) was placed in ether from twenty-four to forty-eight hours, then oven-dried at 56°C. for twenty-four to forty-eight hours, and then weighed when cool. After calcination the percentage of organic material in green bone, the percentage of moisture, ether-soluble and volatile materials was next computed and then the amount of (fixed) organic substance remaining was computed.

The calcination was carried out by the use of two Bunsen burners. The porcelain crucible containing the green or extracted bone was placed on a triangle at an angle of about 45° and just high enough so that the Hght blue cone was close to the crucible. The crucible and contents were warmed gently and then the burner put in a position with some air cut off so that for the first half hour the heat would not be so intense, but sufficient to volatiUze and drive off most of the carbon and volatile substances. These would ignite and burn at the mouth of the crucible. Following this, the air was turned on full to get the greatest heat and another Bunsen with all of the air turned on was held so that the blue cone was directed upon the piece of bone at the mouth of the crucible. Between these two flames the calcining was completed; the bone being turned from time to time. In this way the bone is rendered incandescent and all carbon is burned out. The time varies for different thicknesses from five minutes to half an hour. This is repeated until the weight is constant.- The heat should be carefully appUed at first.

In order to comprehend the following tables the method of determining these various percentages will be first given by an example :


160


H. E. RADASCH


Body 89—1920


Negro Frozen About 35 years of age



Ether — Oven-dried



Bone No.




Femur 90


31.6305 31.6305


4.0670 a 4.0670 a



27.5635 27.9450


3.6845 b 2.4029 d



4.0670 a 3.6845 b


0.3825 c 1.6641 f



31.6305 3.6&15b


f /a = 40.90 per cent organic ma


29.2276 2.4029 d


terial in green bone.



2.4029 d 1.2816 e


c/a = 9.55 per cent moisture, ether-soluble substance, etc.

e/b = 34.78 per cent fixed organic material in the extracted bone.

e/a = 31.51 per cent of fixed organic material in reference to green bone.


In all of the weighings a constant weight (50 grams) was used on the left pan and the right one contained the watch-glass, bone, and weights required to balance the 50 grams.

The various letters indicate the following:

a = The weight of the green bone.

b = The weight of the bone after (1) oven-drying or (2) alcohol-extracting and oven-drying or (3) ether-extracting and oven-drying, c = The weight of the moisture and volatile material alone or (1) -H the

alcohol-soluble or ether-soluble material. d = The weight of the calcined bone. e = The weight of the organic material after (1) oven-drying, or (2)

after extracting and oven-drying, f = Organic material in green bone, f/a = The percentage of organic material and water, volatile and extracted

material in green bone. c/a = The percentage of water, volatile and extractablc material in green

bone, e/b = The percentage of fixed organic material in the dried or extracted

and dried bone. e/a = The percentage of fixed organic in the green bone.

These last two percentages exclude the water and volatile material, and while one percentage is in relation to the weight of the extracted bone, the other percentage is in relation to the weight of the green bone.

The results obtained will be tabulated with reference to age and method employed. Fresh indicates simple postmortem, not embalmed and not preserved in any way ; frozen indicates storage


ORGANIC CONTENT OF COMPACT BONE


161


in the cadaver refrigerator and unembalmed; dissection refers to material taken from cadaver after the dissection was completed.


Green hone Four and one-half months (fresh)


NUMBER


BONE


f/a


REMARKS


7 8


Fe Tib


63.35 66.05


Fresh


At birth (fresh)


Fe


49.61


Tib


50.44


Fe


50.79


Tib


53.07



65.95


Extremit}' of femur consisted mostly of cancellous bone and contained marrow and blood


20 to 60 years


84


Fem


41.15


Negro


85


Tib


41.95


47 years


S4a


Fib


39.85


Frozen


112


Fem


40.61



113


Tib


41.32


Dissection


113a


Fib


40.98






61 to 90 years



11


Fe


40.88


71 years



15


Tib


42.46


Frozen



19


Fem


41.57


Very greasy



23


Feb


44.18


Fresh



24


Tib


44.68


Bones thin, 87 years



31


Fem


43.75




35


Tib


45.25


Frozen



39


Fib


41.56


87 years



43


Fe


42.28




44


Tib


41.40


Fresh. 76 years



45


Fib


41.00




63


Fe


48.62


80 years



64


Tib


45.77


Fresh. Bones thin and buckled


in calcining


66


Fib


41.48




Green Bone— Continued 61 to 90 years


NUMBER


BONE


f/a


REM.4RKS


76


Fe


39.81




77


Tib


41.68


Frozen. 87 years



77a


Fib


40.71




92


Fe


39.44


65 years



93


Tib


41.78


Negro. Frozen



100


Fe


43.39




101


Tib


39.86


Fresh. 89 years



101a


Fib


40.80




Oven-dried hone Four and one-half months


NUMBER


BONE


f/a


c-a


e/b


e/a


REM.\RKS


9 10


Fe Tib


61.23 65.35


27.41 35.04


46.59 46.67


33.82 30.31


Fresh


Eight and one-half months and full term (at birth)


108 109


Fe


52.20


21.50


39.34


30.88


Tib


53.01


22.04


39.70


30.98


Fe


49.22


16.03


39.50


33.19


Tib


50.88


17.15


40.73


33.74


Fe


52.20


19.34


40.72


33.00


Fib


.54.95


25.52


39.55


29.46



66.61


41.59


44.04


25.72


8^ months Fresh

At birth Fresh

At birth Fresh

Extremity femur, cancellous bone


lostly


20 to 60 years


87 87a

114 11.") 11.") a

122 123 123a


Fe


40.57


8.36


35.15


32.20


Tib


40.95


9.29


35.39


31.66


Fib


38.99


8.27


33.49


30.72


Fe


40.28


9.22


34.21


31 06


Til)


40.77


9.59


34.13


30.79


Fil)


40.43


8.34


35.03


32.09


Fe


42 31


7.71


37.01


33.80


Tib


40.65


6.32


36.25


34.24


Fib


41.04


7.85


36.02


33.49


Dissection


162


ORGANIC CONTENT OF COMPACT BONE


163


Oven-dried bone — Continued 61 to 90 years


NUMBER


BONE


f/a


c/a


e/b


e/a


REMARKS


12


Fe


40.70


8.42


35.36


32.44



16


Tib


40.48


lost


lost


lost



16a


Fib


43.36


8.70


37.96


34.66



25


Fe


48.63


9.86


43.51


39.65



26


Tib


46 51


7.61


42.10


38.89



32


Fe


42.28


3.48


40.11


38.66



36


Tib


42 38


8.04


37.34


34.34



40


Fib


40.00


6.85


35.58


33.14



46


Fe


41.19


9.23


35.22


31.97



47


Tib


42.41


11.55


34,61


30.62



48


Fib


41.10


9.78


34.71


31.32



67


Fe


51.50


15.16


42.52


36.10


\Ioisture very high, bones

68


Tib


45.45


11.00


36.76


32.72


shrunk as they calcined


69


Fib


41.85


27.76


19.49


14.82



78


Fe


41.62


12.94


37.74


35.70



79


Tib


39.76


7.81


34.67


31.96



79 a


Fib


39.20


5.79


35.29


33.39



94


Fe


40.01


7.01


35.53


33.05



95


Tib


39.22


6.80


34.77


32.41



95 a


Fib


40.09


7.82


35.15


32.48



102


Fe


40.86


6.40


36.84


34.10



103


Tib


41.42


6.59


37.29


34.83



103 a


Fib


41.44


7.94


36.39


33.38



Alcohol-extracted and oven-dried bom At birth


5


Fe


53.67


23.63


38.70


29.56



6


Tib


53.81


30.08


39.46


27.58



59


Fe


50.36


23.37


38.53


30.32


Extractives high. Can

60


Tib


50.60


19.88


38.34


30.74


cellous bone in one end of sample .


C



68.81


44.92


43.51


23.89


Extremity of tibia. Lots of extractives and moisture


164


H. E. RADASCH


Alcohol-extracted and oven-dried hone — Continued 20 to 60 years


NUMBER


BOXE


f/a


c/a


e/b


e/a


REM.\RKS


88 89

89a


Fe

Tib

Fib


39.66 39.45 38.80


6.28 6.87 8.27


35.22 35.01 33.49


33.00 32.61 30.72



116 117 117a


Fe

Tib

Fib


40.62 41.44 40.09


8.99 9.60 11.17


35.09 35.73 32.69


32.19 32.77 32.42



124 125 125a


Fe

Tib

Fib


42.85 41.07

41.78


8.35 7.24 9.37


37.75 35.94 35.76


34.61 33.28 32.33


Dissection





61 to 90 years



13


Fe


40.01


7.34


35.21


32.66



17


Tib


43.46


9.52


37.41


33.86



21


Fe


41.41


5.53


37.98


35.58



27


Fe


46.55


10.54


40.20


36.04



28


Tib


47.36


10.55


41.40


36.21



33


Fe


40.89


7.11


36.37


33.79



37


Tib


45.01


9.49


39.25


35.53



41


Fib


41.24


8.46


36.31


32.50



49


Fe


41.27


9.88


34.83


31.38



50


Tib


42.09


11.96


24.22


30.12



51


Fib


41.71


10.73


34.69


30.89



70


Fe


47.42


8.37


42.45


38.90



71


Tib


44.77


15.41


34.71


23.78


Eccentric results


72


Fib


43.98


11.74


36.37


32.10



80


Fe


41.02


6.90


36.60


34.13



81


Tib


41.28


8.47


35.84


31.77



96


Fe


40.20


7.47


35.48


32.85



97


Tib


40.36


7.31


35.94


33.31



97a


Fib


40.17


0.09


36.28


33.92



104


Fe


41.04


8.08


35.86


32.19



105


Fib


41.11


8.34


35.75


32.77



105a


Tib


40.42


8.00


35.24


32.42



ORGANIC CONTENT OF COMPACT BONE


165


Ether-extracted and oven-dried hone Eight and one-half months and full term (at birth)


NUMBER


BONE


f/a


c/a


e/b


e/a


REM.^RKS


110


Fe


51.35


20.04


38.95


31.14


8^ months. Fresh


111


Tib


52.44


21.53


39.38


30.73



61


Fe


53.56


23.85


31.35


29.71



62


Hum.


54.48


23.35


40.43


30.91



D



66.57


41.54


41.68


24.96


Extremity of tibia mostly cancellous


20 to 60 years


90 91 91a

118 119 119a

126 127


Fe


40.66


9.55


34.78


31.51


Tib


41.63


10.40


34.88


31.25


Fib


39.46


8.01


34.19


31.45


Fe


41.46


9.43


33.81


30.62


Tib


39.56


9.01


33.94


30.87


Fib


39.49


8.32


33.36


31.17


Fe


42.59


11.58


35.08


31.01


Tib


41.32


8.18


36.66


33.23


to 90 years


14a


Fe


41.84


8.14


36.69


33.70


Frozen


18a


Tib


41.98


7.67


36.85


33.86


71 years


22


Fib


40.76


6.35


36.69


34.40



29


Fe


42.11


9.03


35.23


32.47



30


Tib


42.48


11.29


35.17


31.18



34


Fe


46.62


8.77


34.29


27.86


87 years


38


Tib


39.13


8.80


33.43


30.48


Extractives high


42


FiH


44.70


15.59


34.49


29.09



52


Fe


41.42


11.01


34.19


30.41



53


Tib


41.25


11.64


33.52


29.61



54


Fib


41.29


10.80


34.18


30.49



73


Fe


42.85


15.23


.32.58


27.62



74


Tib


47.89


13.57


39.70


33.56



75


Fib


43.00


15.64


32.54


27.41



166


H. E. RADASCH


Ether-extracted and oven-dried bone— Continued 61 to 90 years


NUMBER


BONE


f/a


c/a


e/b


e/a


REM.VRKS


82


Fe


43.72


13.37


35.05


30.35



83


Tib


43.16


13.26


34.47


39.89



83a


Fib


41.45


12.43


33.15


29.04



98


Fe


40.60


8.17


35.37


32.50



99


Tib


42.31


10.24


35.73


31.71



99a


Fib


40.28


9.04


34.36


31.25



106


Fe


41.21


10.26


34.49


30.05



107


Tib


41.11


10.40


34.82


30.71



107a


Fib


40.61


9.45


34.01


31.26



Cleaned hones of study sets


NUMBER


BONE


f/a


REMARKS


160


Fe


36.73


Quite clean, dry, apparently free from grease, the


161


Tib


36.66


tibia had a little marrow and was greasy around


162


Fib


37.80


the marrow cavity


163


Fe


36.15


Fairly clean


164


Tib


35.72


Clean


165


Fib


34.41


Very clean and dry, like ivory


166


Fe


39.70


Surface greasy to the touch


167


Tib


41.54


Very greasy to the touch. Only partly degreased in


168


Fib


42.08


the boiling




Green bones




Rabbit (two-third grown)


501


Fe


35.87



505


Tib


41.74



509


Fe


37.00



513


Fe


37.66



517


Tib


41.43



Cat (adult)


530


Fe


39.43



531


Tib


39.69



ORGANIC CONTENT OF COMPACT BONE


167


Oven-dried bones Rabbit (two-thirds grown)


NUMBER


BO>fE


f/a


c/a


e/b


e/a


REM.\RKS


502


Fe


35.11


7.85


29.59


27.76



506


Tib


35.08


5.67


31.15


29.41



510


Fib


38.90


10.16


31.98


28.74



514


Fe


40.64


12.81


31.91


27.82



518


Tib


42.07


12.99


33.37


29.04



Cat (adult)


532 533


Fe

Tib


39.10 39.01


9.75 32.37 8.75 33.13


29.31 30.24


Alcohol-extracted and oven-dried bones Rabbit (two-thirds grown)


503 507 511 515 519


Fe


38.78


11.79


30.64


26.98


Tib


38.54


10.58


31.28


27.77


Fe


34.97


9.82


27.88


25.14


Fe


38.38


11.54


30.57


27.04


Tib


40.35


11.33


32.61


28.86


Cat (adult)


534


Fe


39.28


10.40


32.17


28.81



535


Tib


39.49


9.08


33.70


30.75



535x


Tib


43.88


13.03


35.65


31.09


Extremity containing considerable cancellous bone and marrow


Ether-extracted and oven-dried bones Rabbit (two-thirds grown)


508 512 516 520


Tib


41.28


12.27


33.06


28.95


Tib


38.25


9.38


31.88


28.87


Fe


40.24


12.18


33.54


28.08


Tib


41.80


12.56


33.55


29.38


Cat (adult)


536 537 537x


Fe

Tib

Tib


39.04 38.32 42.09


9.90 9.60 11.29


32.35 32.14 34.01


29.14 29.22 30.79


Extremity of shaft with cancellous bone and marrow


168 H. E. RADASCH

DISCUSSION

Green hone

By making a green weight of all pieces of bone used for these determinations, a normal green-weight percentage of the organic material is obtained in all of the different methods of aftertreatment. This not only gives a greater nmnber of results (or a better average) for this determination, but also acts as a check for the other methods. In the opinion of the writer, this green determination is the one that should be used in referring to the organic and inorganic constituents of compact bone.

Fetal hone {four and one-half months)

Upon examining the results of the determinations upon green bone, some very interesting facts are brought out. In the fetus we find that the percentage of organic substance is very high (63.99 per cent), the bone practically consists of two-thirds organic material in the fetus at four and one-half months. This leaves one-third inorganic substance. This is natural, as the bone, before its ossification, is purely organic material. In making this examination great care had to be exercised in preparing the specimen and the weighing had to be rapidl}^ made, as the drying upon the scale pan could be noted. Again, the piece of bone free from the cancellous tissue and marrow necessarily could not be large, as the bones at that age are small.

Bones at term {eight and one-half to ten months)

At eight and one-half months and birth we note that the average is 52.15 of organic material. This is an increase in the percentage of inorganic material with a variation from 49 per cent, or practically half organic and half inorganic substances. This variation, of course, is reasonable, as the diet of the mother has a great influence upon the hardness of the bones of the child. If the mother's diet be rich in bone-forming elements, no doubt the percentage of inorganic material would be raised beyond the above figures.


ORGANIC CONTENT OF COMPACT BONE 1G9

In this table is the determination of bone A. Here the percentage is 65.95. Why is it so high, practically that of the fetus of the fourth to the fifth month? The note in connection with the determination states that this specimen was the epiphyseal extremity of the diaphysis (in contradistinction to the central part usually used) and that it consisted mainly of cancellous bone with its contained marrow. The percentage is practically 15 per cent above the average — a variation too great to be overlooked.

It will be remembered that at the beginning of this paper it was stated that all cancellous bone was removed before the bone was weighed, because cancellous bone contains marrow which could not be removed independently of the bone, and its presence would increase the percentage of organic material if left in the specimen. Marrow is not an organic constituent of bone and must, therefore, be removed. If it is not got rid of, then an inflated per cent of organic content is the result. The determination in the fetal bone (A, table 1) is an excellent example and proof that if a specimen contains cancellous bone, it should be entireh^ discarded or the cancellous bone should be completely removed. Hence the care exercised in the preparation of all specimens before weighing. This same proportionate increase will be seen in the companion determination B, C, and D.

Green hone {20 years to 61 years)

In this group the average per cent is 40.75 of organic substance. These determinations are quite close. The lowest is 38.80 per cent and the highest is 42.85, while most of the determinations are between 40 per cent and 41 per cent. In reference to these variations it might be noted that the tibia giving 38.80 per cent was from an individual 47 years of age and all other green determinations ran along this same rate, all under 40 per cent, showing that the whole series was consistent and not an individual variation due to an accidental loss. In reference to the 42.85 per cent, it might be noted that the age was 60 (border Une), and again all but one were above 42 per cent, again showing a consist


170 H. E. RADASCH

ent figure and not an abnormal variation. Now [this might be due to an unusually great aamount of fat in the marrow and to unusually large haversian canals in the neighborhood of the marrow cavity, containing an unusually large amount of fatty marrow; or again, it might indicate a border-line case in which there is a shght increase of organic material in old age and in this particular individual this increase came on a little earher than usual (an early senescence). In the next series the percentage of one case of 65 years varies between 39 and 40, and, therefore, resembles those of the younger group, indicating a comparatively youthful state.

Green hone {61 to 90 years)

In this group the ages are 65, 71, 76, 80, 87, and 89 years, giving a fairly varied series. Here we find the lowest to be 39.13 in one of 87 years. Determinations were made on the fresh subject and after the remains had been in the cold storage for quite a while; while in the fresh state, the green-bone percentages were consistently high, after freezing the percentages were consistently lower and more like 20 to 61 years of age. A variation in the moisture was also noted under these different conditions.

The highest was 51.50 and 48.03 per cent in two different individuals aged 80 and 87 years, respectively. These are isolated instances which might fairly be thrown out, but still they were retained and included in the series for the reason that this moisture and extractive content were relatively high in each case, seeming to indicate that these figures were not accidental, but in keeping with the other percentages in the experiments. In connection with most of the specimens of the individual aged 83 years, it might be mentioned that upon calcination the bones shrank, curled, or buckled and reacted like the fetal and animal bones where the organic content is relatively high or the bones are relatively thin.


ORGANIC CONTENT OF COMPACT BONE 171

Oven-dried hone

In order to try to obtain as complete a .series of determination as possible, the moisture and volatile organic substances were first removed and then fixed the organic content determined. After the green weight was determined, then all of the desired specimens were subjected to the same heat (drying oven at 56°C.) to remove the moisture and ordinary volatile material (if any such were present). Then by weighing and subtracting the weight from the original green weight, the weight of the moisture and ultimately its percentage were readily determined. Then the amount or weight of the fixed organic material can be obtained. From the weight two results may be deduced : a) the percentage of organic substance to green bone and, b) the percentage of organic substance to the dried bone (green bone less its moisture). These three percentages will be taken in order.

Moisture and volatile organic material (c/a)

Four and one-half months. Here we find the percentage of moisture to average 32.43 per cent. This seems high, but we must remember that the bones are still two-thirds organic material, and organic material, in general, contains a large percentage of free water. We must also remember that the mesenchymal tissues at this stage are largely undifferentiated and so mainly embryonic in character and of a higher water content than at birth and later. We should, therefore, naturally expect a higher moisture percentage.

Eight and one-half months and full term. Here the average is 20.26 per cent with a variation from 16.03 to 25.52. By consulting the table it will be noted that the femur has a lower moisture content than the tibia, probably because the former is older from the developmental standpoint. It will also be noticed that in the eight and one-half months' fetus, the percentages are between those of the two full-term fetuses. This evidently again indicates a difference in the maternal diet. The specimen B represents the epiphyseal extremity of the diaphysis and it consisted mainly of cancellous bone and its contained marrow.


172 H. E. RADASCH

In the moisture content was 41.59 per cent due to the great quantity of blood that could not be removed. This shows why cancellous bone should not be used.

20 to 60 years. In this group while the average is 8.44 per cent, the highest is 9.59 per cent and the lowest 6.32 per cent. The highest amounts were usually noticed in the fresh (unfrozen or unembalmed bodies) and the lowest in those that had been frozen or embalmed. AMiile there seems to be an extraction of moisture from the bones during storage in the refrigerator and an abstraction of moisture from the bones by the embalming fluid in many of the determinations, it is not constant, as will be pointed out later.

61 to 90 years. In this group there is a remarkable variation in moisture content. The average is 8.89 per cent, while the highest is 27.76 per cent and the lowest 3.48 per cent. The former occurred in the tibia of the 80-year-old individual, and this specimen curled and buckled when calcined. The lowest percentage (3.48) occurred in the 80-year-old individual after freezing, and yet other determinations of the same gave as high as 12.94 per cent. This body showed erratic results, so a number of determinations were made by various methods and all were included in the averages.

Although the average of moisture in the group 61 to 90 years is only 0.45 per cent higher than in the 20 to 60 years' group, still that little represents what the proportionate difference should be in comparing their green weights of 40.05 per cent and 42.24 per cent, respectively.

Organic material less water and volatile material in oven-dried hone

Having removed the water and volatile material, the weight of the calcined bone may now be compared with the original green weight and also with the oven-dried weight.

Relations of the organic {less moisture) to oven-dried bone (e/b)

Four and one-half months. If now we determine the percentage of organic substance after removing the water in the oven-dried bone, the average is 46.63 per cent.


ORGANIC CONTENT OF COMPACT BONE 173

Eight and one-half months to full term. In this group the average is 39.92 per cent with a variation from 39,34 per cent to 40.73 per cent — a fairly uniform series.

20 to 60 years, In this group the average is 34.52 per cent with a variation from 33.49 to 37.01 per cent. The former occurred in an individual of 35 years and the latter is one of 60 years.

61 to 90 years. In this group the average is 36.22 per cent with a variation from 19.49 per cent to 43.50 per cent. The cause of the extreme variation could not be determined and, strange to say, the average of these two extremes is nearly the general average.

Relation of organic material (less moisture) to the green weight {el a)

Four and one-half months. In this group the average is 32.06 per cent. By adding this to the percentage of moisture, the result is 63.49 per cent of combined moisture and organic substance proper. The amount given is 63.29 per cent as per the table. All these percentages were obtained by dividing one nmnber into the other and not bj^ mere subtraction, hence the sum of e/a and c/a are not always equal to f/a as they would be by mere subtraction.

At eight and one-half months and full term. The average here is 31.88 per cent with a variation from 29.46 per cent to 33.74 per cent.

20 to 60 years. In this group the average is 32.23 per cent with a variation from 30.72 per cent to 34.24 per cent. The highest were those in the individual of 60 years, the lowest in those of 35 years.

Alcohol extracted and oven-dried hone

This series consists of the results of treating green bone with alcohol for twenty-four to forty-eight hours and then drying for twenty-four to forty-eight hours in an oven at 56°C. and weighing to determine the amount of moisture and alcoholextractable substances and later the 'fixed' organic substance (in relation to the green weight and the extracted weight).


174 H. E. RADASCH

Moisture and alcohol soluble extract (c/a)

At full term. The amount of moisture and alcohol-soluble material averages 24.24 per cent in the child at birth. The lowest is 19.88 per cent and the highest 30.88 per cent. This average represents 3,98 per cent more than the mere moisture and volatile material in oven-dried bones. This does not indicate a high percentage of soluble material, indicating some little fat or oil in the compact bone proper.

20 to 60 years. In this group the average is 8.46 per cent of moisture and alcohol-soluble material. The extremes are 6.28 per cent and 11.17 per cent. The average highest is in those bones of the individual of 35 years of age, while in the subject of 60 years of age they are intermediate. The average is almost identical with the average per cent of plain moisture and volatile substance (8.44), arguing that in individual cases there may be a difference, but in the main (average) that the alcohol-soluble material is very small in quantity.

61 to 90 years. In this group the average is 9.01 per cent with variations from 5.53 per cent to 14.51 per cent. This is higher than the preceding by a half per cent and is only 0.12 per cent above the plain moisture of the oven-dried group. Evidently in the adult the compact bone contains exceedingly little alcoholsoluble substance.

Fixed organic material in alcohol-extracted and oven-dried hone

Relation of the organic substance to the extracted and

dried bone (e/b)

At full term. In this group the average is 38.76 per cent. This is only 1.16 per cent less than the same determination in plain oven-dried bone.

The average here is 29.55 per cent. This is the real organic substance in compact bone of this age. This is 1.51 per cent lower than that of the plain oven-dried bone, indicating some alcohol soluble material in the bone at birth.

20 to 60 years. In this group the average is 32.66 per cent with variations from 30.70 to 34.61 per cent. This is 0.69 per cent


ORGANIC CONTENT OF COAIPACT BONE 175

lower than that of oven-dried bone, meaning that there is verylittle alcohol-soluble substance in compact bone.

61 to 90 years. In this group the average is 32.67 per cent with variations from 23.78 to 38.90 per cent. Compared with the corresponding determination in oven-dried bone, it is 0.59 lower than that.

Ether-extracted and air-dried hone moisture and ether-soluhle substance {c/a)

At term. The average of moisture and ether-soluble substance in compact bone at birth averages 22.19 per cent with variation of 20.04 per cent to 23.85 per cent. This is 2 per cent lower than alcohol-extracted bone and about 2 per cent higher than mere oven-dried term bones.

20 to 60 years. In this group the average is 9.27 per cent with variations from 8.18 to 11.58 per cent. This average is 1.19 per cent higher than alcohol-extracted bone and 1.21 higher then oven-dried bone.

61 to 90 years. In this group the average is 10.87 per cent with variations from 8.17 to 15.60 per cent. This average represents 1.86 per cent and more than that of alcohol extracted bone and 1.98 per cent more than oven-dried bone.

Relation of fixed organic material in ether-extracted hone to etherextracted and oven-dried bone (e/b)

At term. This average is 37.53 per cent as compared with 38.76 in the alcohol-extracted bone and 39.92 per cent in ovendried bones.

20 to 60 years. The average in this group is 34.46 per cent as compared with 35.07 per cent in alcohol-extracted and 36.52 per cent in oven-dried bones.

61 to 90 years. Here the average is 34.83 per cent as compared with 37 per cent in alcohol-extracted, and 46.22 per cent in plain oven-dried bones.


176


H. E. RADASCH


Relation affixed organic material in ether-extracted hone to the green weight (e/a)

At term. The average is 30.60 per cent as compared with the average of 29.55 per cent of alcohol-extracted bone and 31.88 per cent in oven-dried bones.

20 to 60 years. The average is 31.34 per cent as compared to 32.66 per cent in alcohol-extracted bones and 32.23 per cent in oven-dried bones.

61 to 90 years. The average is 30.82 per cent in this group. This is to be compared with 32.67 per cent in alcohol-extracted bones and 33.26 per cent in oven-dried bones.

Cleaned hones

In order to make the study as complete and varied as possible, it was decided to take some of the bones of the study collection sets and determine the organic content of so-called cleaned bones. For this purpose three different sets were chosen, a piece of femur, tibia, and fibula in each set to conform to the preceding tests. One set was as clean and dry as possible (A), a set that showed grease and was greasy to the touch, yet cleaned as the others had been (C), and, thirdly, an intermediate set that looked fairly clean and yet gave indication of some grease (B).


NUMBER


BONE


f/a


REM.\RKS


160 161 162


Fe

Tib

Fib


36.73 36.66 37.80


These seemed quite clean and were apparently free from grease. The tibia contained a little dried marrow and was greasy around the marrow cavity


163


Fe


36.15


The femur was fairly clean


164


Tib


35.72


The tibia was quite clean looking


165


Fib


34.41


The fibula was very clean and dry and looked like ivory


166 167

16S


Fe


39.70


Tib


41.54


Fib


42.08


The surface of the femur was greasy to the touch. The tibia and fibula were very greasy to the touch and only partly degreased in the cleaning


ORGANIC CONTENT OF COMPACT BONE 177

In the test upon the fresh iincleaned bones the corresponding results are as follows:

(e/b) in oven-dried bones:

per cent

20 to GO years 34 .52

61 to 90 j-ears 36.22

(e b) in alcohol extracted and oven-dried bones:

20 to 60 years 35.07

61 to 90 years 37 .00

(e/b) in ether-extracted and oven-dried bones:

20 to 60 years 34.46

61 to 90 years 34.83

In examining these results, interesting facts are noted. In group A, although the bones seemed clean, dry, and free from grease, the results varied. The tibia was the best looking and showed that all of the soluble and volatile substance had been removed and only the fixed organic material had been left. The percentage of fixed organic material in this bone was 34.41 per cent. This is practically identical with the percentage of fixed organic material in the ether-extracted bone and seems to indicate the complete extraction of all but the fixed organic substance. As we look through the other percentages we see the effect of the presence of unnoticeable and distinctly noticeable quantities of grease that remain through the incomplete cleaning of bones. Naturally, any such retained grease will have weight and will necessarily be included in percentage of fixed organic substance, though it should not be so included.

Another interesting fact is that in cleaning bones by boiling or macerating in water alone, all bones of the same body do not degrease or clean equally. Again some bones on repeated treatment seem to retain the grease to a considerable extent. ■ From this series it will readily be granted that the ordinarily cleaned bones are not satisfactory as a standard for the determination of organic substance in compact bone for bones that seem dry, clean, and free from grease may contain 1 or 2 per cent, and so change the final determination.


178 H. E. RADASCH

Other mammals

As some rabbits and cats were available at the time these determinations were made, it was decided to carry out the same series of tests upon the corresponding bones of these animals. The bones were prepared and treated in the same way and the tests were identical in all respects. The bones of these animals, however, are more difficult to handle. They are thin and bulky so that the amount of bone by weight was not great, varying from 0.1 gram to 0.5 gram. This did not allow a very great leeway for variations. Another prominent feature was that the bones at the first heating curled and spht, and if the heat was iiot cautiously appUed, small pieces might readily fly off and be lost. Also at the first heating the small areas of the bone that touched the crucible seemed to stick, but this did not seem to make any appreciable variation in the result.

The bones clean readily, as the periosteum strips with ease and the marrow comes out in toto as a plug would. There is no cancellous bone around the narrow cavity to be whittled away as in the human bone, so that the preparation of these bones is not so tedious a process as in the case of the human bones.

The weighing, however, must be rapidly carried out, as in the case of fetal bones, for these bones seem to contain a little higher percentage of moisture (as fetal bones) than the adult human bone. Perhaps this is only apparent and their thinness gives a greater proportionate surface for evaporation and so influences the result. There is no difficulty in getting the real green weight, however.

Rabbit. The rabbits used were all about two-thirds grown and represent the human at about the age of puberty. They were all in good health and were well developed. They had been utihzed for other experimental work, but this had no influence upon the tests in hand.

Green bone. In this group the average of all of the bones tested was 38.90 per cent of organic substance, somewhat lower than we would expect to find it at the corresponding age of the human being.

The other determinations will be considered as follows :


ORGANIC CONTENT OF COMPACT BONE 179

Moisture and volatile and extractable substances

In oven-dried bone the average was 9.89 per cent.

In alcohol-extracted and oven-dried bone the average was 1 1 per cent.

In ether-extracted and oven-dried bone the average was 11.60 per cent.

Relations of the fixed organic substances to the extracted and dried bone (e/b)

In ven-dried bone the average was 31.60 per cent.

In alcohol-extracted and oven-dried bone the average was 30.58 per cent.

In ether-extracted and oven-dried bone the average was 33.01 per cent.

Relation of the fixed organic substance to the green bone (e/b)

In oven-dried bone the average was 28.56 per cent.

In alcohol-extracted and oven-dried bone the average was 27.16 per cent.

In ether-extracted and oven-dried bone the average was 28.82 per cent.

Cat. In the course of the laboratory work several cats were used for tissue purposes and so at the time the corresponding bones were prepared, as in the human, for these determinations. They were of adult age, well developed and apparently healthy.

Green bone. The average of all the bones tested was 38.32 per cent — somewhat low — even than the corresponding average in the human being.

Moisture, volatile, and extractable substances (c/a)

In oven-dried bone the average was 9.25 per cent.

In alcohol-extracted and oven-dried bone the average was 11.01 per cent.

In ether-extracted and oven-dried bone the average was 11.60 per cent.


180 H. E. RADASCH

Relation of fixed organic substance to the extracted and dried hone

ie/b)

In oven-dried bone the average was 32.75 per cent.

In alcohol-extracted and oven-dried bone the average was 33.84 per cent.

In ether-extracted and oven-dried bone the average was 32.83 per cent.

Relation of fixed organic substance in extracted bone to green bone (e/a)

In oven-dried bone the average was 29.77 per cent.

In alcohol-extracted and oven-dried bone the average was 30.22 per cent.

In ether-extracted and oven-dried bone the average was 29.72 per cent.

Having compared the results obtained by the different experimental methods, it will now be of interest to consider the determinations from another standpoint, according to the following tables: Here only the adult human results and cat and rabbit will be considered.

per cent

Average in green bone at 20 to 60 years 40.75

Average in green bone at 61 to 90 years 42 .32

Average in green bone in rabbit 38.90

Average in green bone in cat 39 . 85

Moisture and extractable substance {c/a)

Average in oven-dried bone 20 to 60 years 8.44

Average in oven-dried bone 61 to 90 years 10.18

Average in oven-dried bone, rabbit 9.89

Average in oven-dried bone, cat 9.25

Average in alcohol-extracted bone, 20 to 60 years 8.46

Average in alcohol-extracted bone, 61 to 90 years 9.01

Average in alcohol-extracted bone, rabbit 11 .01

Average in alcohol-extracted bone, cat 10.84

Average in ether-extracted bone, 20 to 60 years 9.27

Average in ether-extracted bone, 61 to 90 years 10.87

Average in ether-extracted bone, rabbit 11.60

Average in ether-extracted bone, cat 10.26


ORGANIC CONTENT OF COMPACT BONE 181

Relation of fixed organic substance to dried and extracted bone {e/b)

Average in oven-dried bone, 20 to 60 years 35 . 17

Average in oven-dried bone, 61 to 90 years 36.22

Average in oven-dried bone, rabbit 31 .60

Average in oven-dried bone, cat 32.75

Average in alcohol-extracted bone, 20 to 60 years 35.07

Average in alcohol-extracted bone, 61 to 90 years 37.00

Average in alcohol-extrcated bone, rabbit 30.58

Average in alcohol-extracted bone, cat 33 .84

Average in ether-extracted bone, 20 to 60 years 34.16

Average in ether-extracted bone, 61 to 90 years 34.83

Average in ether-extracted bone, rabbit 33 .01

Average in ether-extracted bone, cat 32 .83

Relation of fixed organic substance to the green bone (e/a)

Average in oven-dried bone, 20 to 60 years 32.23

Average in oven-dried bone, 61 to 90 years 33 . 15

Average in oven-dried bone, rabbit 28.56

Average in oven-dried bone, cat 29.77

Average in alcohol-extracted bone, 20 to 60 years 32.66

Average in alcohol-extracted bone, 61 to 90 years 32.67

Average in alcohol-extracted bone, rabbit 27.16

Average in alcohol-extracted bone, cat 30.22

Average in ether-extracted bone, 20 to 60 j'ears 31 .34

Average in ether-extracted bone, 61 to 90 years 30.82

Average in ether-extracted bone, rabbit 28.82

Average in ether-extracted bone, cat 29.72

Green weight (f/a)

In this table the average amount of organic substance and moisture in green bone (between 20 and 60 years) is 40.75 per cent. This is 6 per cent to 7 per cent higher than that given in text-books. Of course we must admit that this includes moisture and volatile substance and perhaps a very small amount of fat or oil that could not be removed by mere physical means. The specimens were prepared as carefully as possible, and the writer feels that the bone so prepared is standard for all green-weight determinations. The question naturally arises, Should we include moisture and volatile substances in the per cent of organic material?" Just where to draw the line seems impossible to determine. The small quantities of fat and marrow in


182 H. E. RADASCH

perimedullary haversian canals cannot be removed in this method and they are counted in as part of the organic constituent, and yet they should not be and we are helpless in any effort to remove them.

Again in comparing the results at the prime and after, we find that in the latter instance the average is 42.32 per cent — somewhat higher than in the preceding. This argues for a slightly smaller inorganic content and would argue in favor of the reduction of inorganic as being a factor in the readiness with which the bones of the old fracture made only sUght strains. Although the reduction is not so great as to give positive assurance of this, still we must take it into consideration as a possibility. More determinations along this line will be made as the material presents itself.

In comparing the results in the human and in the rabbit (two-thirds grown) we note that in the latter the average percentage of organic material is 38.90 per cent. This indicates immaturity in development and would compare favorably with like stages in the human being, no doubt. Unfortunately, no material was obtainable in individuals from birth to 20 years. From the closeness in the averages, no doubt the per cents in the adult rabbit came very close to that of the human being — showing a close relation in mammals apparently.

In the adult cat the percentage was 39.85 — less than 1 per cent below that of the human. If as many determinations had been made in the cat as in connection with human bone, the writer beheves that the difference would have been even less, indicating a close relationship in mammals with reference to the composition of compact bones.

Moisture and volatile and extractaUe substance (c/a)

In this table the average moisture in compact bone in those 20 to 60 years of age is given as 8.44 per cent.

The temperature (o2°C.) is not sufficiently high to cause any decomposition, nor was it employed long enough to cause any untoward effects upon the above. Whether anything else


ORGANIC CONTE'NT OF COMPACT BONE 183

besides moisture is driven off or not was not determined, as that was bej-ond the province of this paper. This amount of moisture strikes one as quite high, j^et when we consider that all of our organs and tissues are principally^ water (mainly combined) we should not be surprised at these results. It is variable in different individuals, as the detailed results in the earher tables show. If this be not considered normal organic content, but be subtracted from the green weight, then the average, as will be seen later, gives what is normally called 'fixed organic substance.'

Between the ages of 61 and 90 the percentage of moisture, etc., is 10.18 per cent, and as we proceed in this analysis we will note that the increase in these ages is constant. The difference between these age groups is only 1.75, yet that is a definite increase.

In the rabbit the average moisture, etc., is 9.89 per cent, and this does not seem excessive for the proportionate growth, as the percentage in the young is greater than in the adults and then in old age seems to increase again.

In the cat the amount of moisture is 9.25 — nearly 0.75 per cent greater than in the adult man. This is possibly a normal condition for that animal.

In the alcohol-extracted bone the percentage is ahuost identical with that of oven-dried bone, being only 8.46 per cent. It seems that compact bone prepared in the v^-ay for these determinations contains very little alcohol-soluble substance. In those of '61 to 90 years the percentage is only 9.01 — below the weight of ordinary moisture. This variation cannot be accounted for.

In the rabbit the average is 11.01 per cent and in the cat 10.84 per cent, showing over 1 per cent increase in both instances. Again, the relativeh' higher percentage in the rabbit indicates a more youthful state.

The ether-extract able substance is greater. In the human bone 20 to 60 j^ears the average is 9.27 — a material increase over moisture and alcohohc extract. This increase is constant in all. In the rabbit the average is 11.60 per cent, in the cat 10.26 per cent. In all of these forms of animals there is a higher percentage


184 H. E. RADASCH

of ether-extractable substance, and this probably is the fat in the perimedullarj^ haversian canals. This amount of etherextractable substance is material in relation with total amount of moisture, but in reference to the total amount of organic substance it is not so marked. We must, however, reahze that there is some ether-soluble organic material even in the compact bone and something Avhich is difficult to classify, so the question arises, "Should it be included in the organic constituent or not?"

Relation of fixed organic substance to the dried and extractable bone (e/b)

As has been seen, the percentage of organic substance in green bone includes the moisture and soluble substances, and this naturally increased that percentage. Should they be included as organic constituents or excluded? If we exclude them, then we have remaining the real fixed organic substance and then we can deduce two different answers: 1) The relation of this fixed organic substance to the weight of the extracted bone (green bone less moisture and extracted substance e/b) : The relation to the original green weight (without the removal of any moisture, etc., e/a).

Of course, the percentage in. reference to the extracted bone weight (e/b) will be the greater and we find that the percentage in those 20 to 60 years is 35.17 per cent. This is a per cent or so above that given in text-books, but M'e are not told the method of determination, and the writer for one, does not believe that this was the method used. In those of 61 to 90 years the average is 36.72 per cent — again higher than in the earlier j'ears. In the rabbit it is 31.60 and in the cat it is 32.75 per cent — considerably lower than in the human bone.

In the alcoliol-extracted bone in those 21 to 60 years, the average is 35.07 per cent, while in those 61 to 90 years, the average is 37 per cent. Again, this determination shows less alcoholic extract than mere moisture as in the last table. This seems to indicate that alcohol may fix and render insoluble or non-volatile


ORGANIC CONTENT OF COMPACT BONE 185

some substances in the bone that are volatile with mere heat or soluble in ether. So the figures would argue at any rate. In the rabbit the average is 30.58 per cent and in the cat 33.84 per cent. In the ether-extracted bone, 20 to 60 years, the average is 34.16 per cent of organic substance as compared with the extracted weight of the bone. At 61 to 90 years the average is 34.84 per cent in both instances^ — a drop over the corresponding moisture and alcohol-extracted percentages. This is in keeping with the relatively higher amount of ether-extractable material, and should be so. In the rabbit the average is 33.01 per cent and in the cat 32.83 per cent. These are properly proportionate results.

Relation of the fixed organic substance to the green weight (e/a)

In these results the percentages should be lower than in the preceding, as we start with a higher original weight, including therein all moisture and extractable substances. In those 20 to 60 years of age the average is 32.23 per cent and in those 61 to 90 years the average is 33.15 per cent.

In the rabbit the average is 28.56 per cent and in the cat 29.77 per cent.

These percentages could all have been got by merely subtracting the percentage of moisture from the original average in green bone, but this was not done, but each was determined from the resulting weights, so in some instances the sum of the moisture percentage and this last per cent (e/a) does not always give the exact per cent of organic substance in green bone, but the per cent according to the figures obtained. We note in all these last determinations a constant and normal difference from the preceding determination.

In the alcohol-extracted bone, 20 to 60 years, the average is 32.66 per cent and in those of 61 to 90 years the average is 32.67 per cent — almost identical. In the rabbit the average is 27.16 per cent and in the cat 30.22 per cent.

In ether-extracted bone, 20 to 60 years, the average is 31.34 per cent and from 61 to 90 the average is 30.82 per cent. In


186 H. E. RADASCH

the rabbit the average is 28.82 per cent and in the cat 29.22 per cent. These are all consistent variations and will be noted by consulting the corresponding table in the other methods of determination.

CONXLUSIOXS

Five methods for the determination of organic content of bone have been here given. Of these the ordinary- method of cleaning (maceration) should be avoided, as results cannot be consistent owing to the irregularitj^ with which bones of the same individual degrease.

All of the other four methods are constant and reliable, and every one may be considered as a standard. Various points for discussion arise. Should the moisture be included in the organic content? Should any alcohol- or ether-soluble substance be included in the organic content?

If we examine the tables, we find that the only percentages close to those given in text-books are those obtained in etherextracted bone and in relation ^o the weight of the bone after extraction by the ether (e/b).

This may have been the method employed by the early chemists. It was employed here to try to determine the nearest to the text-book percentages. This determination (e;'b) may seem unfair because it first removes the soluble and volatile substances and takes the weight of this dried bone as a standard to determine the fixed organic substance. It does not seem fair, but it discriminates against volatile and extractable substance. It can be argued that this moisture and this soluble material are real organic contents and that they should be so included just as in making an assay of ore, the whole sample is crushed and mixed for test and not just certain parts selected. In the latter instance any desired results could be obtained and these would not be the true or fair results. If the moisture and soluble material be considered organic content, then our text-books are incorrect to the extent of 6 per cent to 7 per cent. If, on the other hand, they are excluded and the percentage still be determined in the green weight, then the text-book percentage is 2 to 3 per cent too high. Even in oven-dried bone the percentage in reference to the dried weight is still too high — 37.15 (20 to 60 years) and 36.22 (61 to 90 years).

The writer would be inclined to consider the green weight the proper one for starting. After the bone has been freed of all periosteum and cancellous tissue and surface oil, its weight should be the one used, and the ultimate results would come under the determinations f/a, in which the average is 40.75 per cent (20 to 60 years) and 42.32 per cent (61 to 90 years).

The writer would hke to have the opinion of others along this line so as to estabhsh a standard for determination of the organic content of compact bone. Further studies in this connection are under way.


Resumen por el autor, Eben J. Carey.

Estudios sobre la estructura y funcion del intestino delgado.

I. La arquitectura helicoidal del intestino delgado. II. La acci6n espiral del intestino delgado.

La capa muscular interna del intestino delgado es una lamina continua arrollada en espiral apretada. Una vuelta completa de espiral tiene lugar en cada 0.5 a 1 mm. de longitud, o menos. La capa muscular externa forma una espiral alargada, que termina una vuelta completa en una extension de unos 200 a 500 mm. o mas. La submucosa esta compuesta de fibrillas de tejido conjuntivo que forman una espiral interna apretada y otra externa mds laxa. La interna efectua una vuelta completa en 0.5 a 1 mm. o menos, la externa en cada 4 a 10 mm. La capa muscular interna, por consiguiente, esta arrollada en espiral apretada, la externa en espiral laxa.

La diferencia en la velocidad de la progresion translatoria de las dos ondas de contracci6n depende de esta disposici6n en espiral. La onda que marcha a lo largo del grupo interno de fibras toma un curso rotatorio, mientras que la que camina a lo largo de las fibras externas sigue una direccion mas translatoria hasta alcanzar su punto de destino. Por consiguiente, la contracci6n de la capa muscular interna, mas fuerte, seguira inevitablemente a la de la capa externa. La disposicion de las capas musculares intestinales explica claramente el fenomeno de la contrisci6n cefalica y la dilataci6n caudal durante la diastasis, sin necesitar invocar la ayuda de vias nerviosas hipot^ticas. La peristalsis, por consiguiente, es un fen6meno de doble contracci6n producido por la velocidad diferencial del avance translatorio de las dos ondas de contraccidn en las capas musculares externa e interna, respectivamente. Estas conclusiones se basan en experimentos en los cuales el autor separ6 del intestino vivo las capas externa e interna.

Translation by Jos6 F. Nonidez Cornell Medical College, New York


Studies On The Structure And Function Of The Small Intestine

EBEN J. CAREY Department of Anatomy, Marquette University, Medical School, Milwaukee

TWENTY-TWO FIGURES

CONTENTS

1. Helicoidal architectonics of the small intestine 189

Introduction 189

Observations on the helicoidal structure of the intestine 191

Conclusions 193

2. The screw-like action of the small intestine 194

Introduction 194

Experimental observations 196

Interpretations 200

The reciprocal elongation of muscles 203

Direct observations of peristalsis 204

Conclusions 213

3. Literature cited 215

1. THE HELICOIDAL ARCHITECTONICS OF THE SMALL INTESTINE

Introduction

The current literature and text-books of anatomy and the related medical sciences describe the two muscular coats of the small intestine as "inner circular and outer longitudinal." The inner muscular coat is conceived, therefore, as forming a tube composed of discrete muscular rings with a certain degree of connection. Such a conception is a faulty anatomical heirloom and, due to its apparent truth by a mere cursory microscopical observation, is accepted by the present generation as an assimilated fact. This erroneous idea arose with the inception of the microscope and has since been accepted unchallenged. Mall ('96) demonstrated the spiral nature of the submucosa twenty 189

THE ANATOMICAL RECORD, VOL. 21, NO. 2


190 EBEN J. CAREY

five years ago, but this important observation has remained as an obscure isolated report. The fact that the musculature possesses also a spiral architectonic did not occur to him.

The truth in regard to the form of a muscular structure is impossible when the evidence rests on microscopic observations of single sections. Painstaking reconstructions of serial sections may be an aid, but only when it is impossible to make gross dissections. The pitfall presented by the microscope reminds one of the following wise admonition given by John Goodsir ('46) to his freshman class in anatomj^, "As soon would the astronomer place the telescope in the hands of his pupil and request him to interpret the sinuous lines by which the orbits of the planets are projected on the apparent surface of the hollow sphere, before he has acquired steady ideas of astronomical forms and motions by preparatory study, as would the judicious teacher of anatomy suggest the examination of objects by the microscope before strict anatomical ideas of form and relation had been acquired by the study of the gross specimens of the bones, viscera, muscles and blood vessels."

Studies on the interaction of the intestinal components (Carey, '19,-'20 a; '20 b; '20 c) during the genesis of these two muscle coats reveal the following facts: The primitive gut presents two zones of differential rates of growth. There is an inner epithelial tube, growing in the manner of a left-handed spiral, of accelerated growth. Secondly, there is the outer mesenchyme, of retarded growth, from which the two muscle coats are derived. During the period of rapid transverse growth of the inner tube, the inner muscle coat is seen to become progressively drawn out by traction. This coat, then, by compression, restricts the diametrical growth of the entodermal tube. The planes of mitosis shift from a parallel to a transverse position as regards the long axis of the gut and the subsequent growth of the inner tube is relatively more rapid in length than in width. During this rapid longitudinal growth, the outer mesenchymal cells are drawn out by traction, revealing the first step in histogenesis, namely, an elongation of the myoblastic cell.


STRUCTURE AND FUNCTION OF SMALL INTESTINE 191

Since, the tension in the mesenchyme corresponds to the spiral lines of the dominant growth-force, of the entodermal epithehal tube, the mature structure, as the muscular resultant of this interaction of growth and resistance, under no circumstances could possess a circula form. This assertion is based purely on embryological evidence. The confirmation of this evidence led to the following observations of gross dissections.



Fig. 1 Schema of the left-handed helicoidal structure of the small intestine based on dissections. The mitosis of the epithelial tube follows the path of a left-handed helix. Mucous folds are directed the same as the mitotic paths. This is seen in the valvulae conniventes which primarily form left-handed interdigitating spirals. This is readily demonstrated by everting the duodenum or jejunum. The submucous connective tissue forms inner close spirals and outer elongated spirals. This same arrangement holds for the muscular coats. The fasciculi of the muscular coats and the fibers of the submucous coat are connected by anastomosing elements, respectively. Muscular action based on this arrangement, therefore, is in the manner of a screw corresponding to the direction of the muscular fibers.

Direct observations on the helicoidal structure of the muscle coats of the small intestine

The small intestine of the pig is everted over a test-tube. By making a longitudinal incision through the mucosa and the submucosa these coats are then easilj^ dissected from the inner muscular layer. Once the inner muscular layer is thoroughly cleaned of submucous and areolar tissue, a single smooth muscular fasciculus may be easily isolated and traced around the test-tube. By this means one may demonstrate incontestably that the fasciculi of the inner smooth muscle coat are wound closely in a compact spiral (fig. 1).

The main point to keep in mind in regard to this arrangement in the adult is that it reflects its embryonic origin. The muscle is derived from an embryonic syncytium which had been whorled


192 EBEN J. CAREY

into a vortex. Consequently, there is bound to be intercommunications found between the spirally arranged fasciculi in the mature state.

In many instances one may trace a well-developed smooth muscle fasciculus in the duodenum or lower ileum near the cecum as a definite entity through ten or fifteen turns. This demonstrates that the inner intestinal muscular coat is not composed of discrete contiguous rings, but is a continuous syncytial muscular layer spirally wound anticlockwise.

By inserting a test-tube in the lumen of the intestine and dissecting off the serosa it may be demonstrated that the fasciculi of the outer coat do not run a straight longitudinal course, but run slightly in an oblique direction. In many instances a definite fasciculus or group of fasciculi may be traced from one side of the intestine to the other. There is a tendency to obliterate the spiral nature of the outer coat due to the torsional reaction of the intestine. This is manifested by the formation of loops which tend to counteract the strain to which the intestine is subjected in the spiral development of the entodermal epithehal tube. At the same time, this reaction tends also to counteract the spiral course of the outer layer.

The inner layer makes a complete turn in every 0.5 to 1 mm. or less; the outer layer makes a turn in every 200 to 500 mm. The definite obliquity of this outer layer is best detected after cleaning thoroughly along the line of the mesenteric attachment. It is then clearly demonstrable that the outer fasciculi do not run in a longitudinal course parallel to this landmark, but at an acute angle from right to left (fig. 1).

The spiral nature of the connective tissue of the submucosa may be demonstrated by inserting a test-tube in the lumen of the small intestine and dissecting off the serosa and musculosa. By allowing the submucosa and mucosa to incubate at 37°C, autolysis will occur, leaving the fibers intact. As desiccation proceeds, the fibers adhere to the test-tube, forming two definite spiral arrangements. There is an inner close spiral and an outer elongated spiral both wound anticlockwise or as a left-handed helix.


STRUCTURE AND FUNCTION OF SMALL INTESTINE 193

Mall ('96) detected the spiral nature of the submucosa, but described it as composed of fibrillae running in opposite directions, forming a spiral lattice-work. The observation of the spiral nature is correct, but the fibrils are arranged in two sets running in the same direction. The inner spiral is wound closely, the outer is more elongated. The latter makes one complete turn every 4 to 10 mm. the former in every 0.5 to 1 mm. or less (fig. 1).

Conclusioi2s

1. The inner muscle coat of the small intestine is not composed of circular or annular rings contiguously placed, but is a continuous muscular sheet wound into a close helix. One complete turn is made in every 0.5 to 1 mm. or less.

2. The outer muscle coat of the small intestine is not composed of longitudinal fibers parallel to the long axis, but of elongated fibers, at an acute angle to the long axis of the intestine, which tend to pursue a spiral course. This spiral character is obhterated in many places, due to the torsional reaction of the intestine. Those which are spirally disposed make a complete turn in every 200 to 500 mm. or more.

3. The submucosa is composed of connective-tissue fibrils forming an inner close and an outer elongated spiral. The inner makes one complete turn in every 0.5 to 1 mm. or less, the outer in every 4 to 10 mm.

4. Therefore, the structure surrounding the epithehal tube of the intestine in the mature state possesses a spiral nature arranged as a left-handed hehx with an inner close and an outer elongated set of spirals in both the submucosa and musculosa.

5. The valvulae conniventes of the duodenal epithehum are arranged as interdigitating spirals.

6. In the adult, consequently, confirmatory evidence is presented substantiating the thesis that the left-handed hehcoidal growth of the epithelial tube creates a corresponding mesenchymal vortex. From the latter the spiral structure of the submucosa and musculosa is developed. This competition between the accelerated growth of the entodermal tube and the


194 EBEN J, CAREY

retarded growth of the surrounding mesenchyme leading to a formative interaction of differential growth has been overlooked as a factor in histogenesis.

2. OBSERVATIONS ON THE SCREW-LIKE ACTION OF THE SMALL INTESTINE

Introduction

Since the direction of muscular contraction is dependent on the form and arrangement of the muscular fasciculi, it will be profitable to study intestinal action in the Ught of the spiral architectonics of the musculature. Form and function are inseparable; consequently, a contribution to anatomical structure is an aid to understanding its related function.

The study of the reciprocal elongating actions of the two muscle coats of the intestine presents one of the most confusing chapters in the entire hterature of anatomy and physiology. Prior to the graphic records obtained by Bayliss and Starling ('99 a) it was thought that the outer and inner muscle layers contracted alternately by Ludwig ('61), Englemann ('71), Nothnagel ('82), Luderitz ('89), Mall ('96 a). Bayhss and Starhng proved that these muscle layers contract simultaneously. But they interpreted their classical records by stating that contraction takes place in the two muscular layers in the same place at the same time. Although contractions begin in the two layers at the same position at the same time, the typical peristaltic resultant is at different locations in successive units of time. This will be proved to be inevitable because of the arrangement of the two sets of muscular fascicuh.

There are three main types of movement seen in the small intestine. First, there is a rapid vermicular wave. This is primarily seen after death or in animal experimentation. It progresses through the course of the small intestine in about a minute. It is considered by Alall ('96 b) as being more pathological than physiological. Second, there is the slow -moving peristaltic wave called by Cannon ('12 a) diastalsis. This normal wave propels the food through the small intestine in three to five hours. Third, there is seen rhythmic segmentation which may or may not be combined with peristalsis. By combination of the two movements there is a slow^ advance of the food combined with definite constrictions of the intestinal contents. There is a rhythmic repetition of the segmentation. Normally, the wave progresses from above downward.

The slow peristaltic wave presents a marked constriction above and a marked dilatation below the stimulated area. This phenomenon has been called by BayHss and Starhng ('99 b), the 'law of the intestine.' They state this law as follows: "Local stimulation of the gut produces excitation above and inhibition below the excited spot. These effects are dependent on the activity of the local nervous mechanism."

That Bayhss and Starling ('99 a) exclude absolutely the fundamental arrangement of the two muscular layers as shedding light on the interpretation of the peristaltic wave is seen in the following statement (p. 114): "We cannot imagine any muscle fibre or collection of muscle fibres w^hich would relax on one side and contract on the other side of an excited point."

Bayliss and Starling ('99 d) invoke, therefore, the aid of hypothetical nerve paths to explain the apparent paradox as follows (p. 115): "The different time relations of the two reflex actions would lead one to guess that the system is composed of long paths which conduct inhibitory impulses downwards, and short paths which carry augmentor impulses from one cell station to another in an upward direction." After tw^enty years no objective histological evidence has been presented confirming the nerve paths assumed by Bayliss and Starhng in their interpretation of the peristaltic complex.

]Magnus ('04) proved that Meissner's (submucous) plexus is not involved in the production of the slow peristaltic wave. It was modified or inhibited by sectioning the vagus nerve and by the use of nicotine. Consequently, the true peristalsis IMagnus considered as due to Auerbach's (myenteric) plexus. Cannon ('12 b) therefore called the 'law of the intestine' the myenteric reflex.


196 EBEN J. CAREY

That Mall ('96 c) surmised the active influence of the muscular arrangement in the propulsion of food through the intestine is seen in the following:

"It therefore seems that there are at least two forces which move a body through the intestine. 1. The body as an irritant causes the circular muscles above it to contract, which in turn pushes the body down. A new portion of the mucosa is irritated, which causes a new contraction and so on. 2. At the same time a sucking force, due to an active dilatation below the body, may have a tendency to drag it down."

Mall, however, did not reveal the factor causing the active dilatation. Cannon ('02 c) pointed out this discrepancy in Mall's argument, as follows: "In what manner an active dilatation of the intestinal wall may occur so as to produce a 'sucking force,' IMall does not wholly make clear." At the same time. Cannon also refrained from clearing up the question at issue.

The object of this paper, therefore, is to report results of experiments and of direct observations of the musculature of the small intestine in the hght of the spiral architectonics of the two muscle layers. The law of the intestine or myenteric reflex is proved to be an inevitable duplex contraction phenomenon based on the fact that the inner coat is a close spiral and the outer an elongated spiral or longitudinal muscle layer. This arrangement of the two sets of muscles results in a differential rate of translatory progression of the two contraction waves in the outer and inner coat, respectively. The wave in the outer coat will pursue a greater longitudinal distance per unit of time than that in the inner coat, because the wave in the inner coat pursues a more rotary course, to reach the same destination, than that in the outer coat.

Experimental observations

A. Experimental exsection of the inner close spiral muscular coat of the intestine. The following observations are true for the dog, cat, pig, sheep, and cow. About a foot of the small intestine was inverted under warm oxygenated Ringer's solution soon after the animal was killed. The mucosa and submucosa were


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197


quickly dissected, making an annular gap of about 1 inch. By making two longitudinal incisions, one along the mesenteric and the other opposite the mesenteric attachments through the inner spiral coat, the latter may be quickly dissected from the outer coat. The gut is then rein verted to its normal position (fig. 2). After a quick, clean dissection and if the excitabiHty of the musculature is still present, a satisfactory demonstration may~be made (figs. 2 and 3).



Fig. 2 This represents a segment of the gut from which the inner spiral coat was exsected between a and h. The arrow is directed caudad.

Fig. 3 This represents a peristaltic wave in relation to the area of exsection of the inner close spiral muscle coat, a' designates the cephalic constriction. From a' to h' depicts the caudal dilatation. This bulging immediatelj^ evident is due to the outer elongated muscle layer. A stimulus applied to the muscle layers of the gut will produce two effects due to the different directions of the muscular fasciculi. The reacting contraction wave of the inner coat will pursue a rotary course, whereas that of the outer coat will pursue a translatory course. Therefore, the cephalic constriction produced by the contraction of the stronger inner coat is bound to trail the caudal dilatation produced by the outer coat.

Stimulating by pinching or by inserting a vaselinated cotton bolus or by means of the induction current, a peristaltic wave may be started above the annular exsected area. The dilatation is immediately detected below the stimulated spot and constriction above. It is definitely evident by direct observation that the outer muscle coat contracts in advance of the inner muscle coat as the constriction nears the annular area of exsection. The constriction due to the stronger inner coat is cephalad or proximal to the area of exsection, at the same time that the outer muscle


198 EBEN J. CAEEY

coat contracts caudad or distal approximating the edges of the exsected region a' to b" (fig. 3).

Simultaneous with the approximation of the edges of the exsected area there is a tendency to bulging. This bulges primarily outward, but may bulge inward. This is comparable to the bulge of the fibrils of a twisted string when reheved of the torsion. The fibrils as they unwind tend to give a characteristic spindle-shaped bulging. That a shortening of the outer coat takes place in advance of that of the inner coat is, therefore, objectively evident.

This experiment proves that the active contraction of the outer coat is a definite factor in the production of the caudal dilatation seen in the intestinal peristalsis. The constricted, cephalic component is usually blocked upon reaching the exsected region, in a few instances a slight propagation was detected distal to the exsected region, showing that the elongation of the inner coat produced by the contracting outer coat had taken place. If only a 5- or 10-mm. annular gap is made, the wave is not as frequently blocked as when 30 or 40 mm. are exsected.

The inner and outer coats act, therefore, as reciprocal elongators during the propagation of the peristaltic wave. The integrity of each muscle is necessary for normal peristalsis. Normal peristalsis is a double contraction wave. - The wave of contraction of the inner coat, following the path of a close spiral, trails that of the outer coat which follows the path of an elongated spiral. The contraction of the inner coat causes the cephalic constriction, that of the outer coat the caudal dilatation.

B. Experimental exsection of the outer elongated spiral muscle coat. The small intestines of the same animals are used as in the foregoing experiment. The serosa and outer muscular layer are exsected under warm oxygenated Ringer's solution. Two circular incisions of varying distances are made. The incisions are connected by means of two longitudinal incisions, one along the mesenteric and one opposite the mesenteric attachment. The incisions extend to the circular coat. A quick dissection of the serosa and outer muscle layer is now made, leaving the inner muscle layer between the circular incision (fig. 4).


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By now stimulating the intestinal tube as before, the typical cephalic constriction and caudal dilatation of the peristaltic wave are started down the tube in the normal direction caudad. In figure 5 the peristalsis is seen a few millimeters from the ex


Fig. 4 Diagram of gut from which the outer muscular coat was exsected from a to b.

Fig. 5 Diagram of peristaltic wave bordering the area in which the outer muscle layer is absent. Note especially that the caudal dilatation is shortened and totally lacking over the area in which the outer muscle layer was exsected.

Fig. 6 The cephalic constriction of the peristaltic wave borders the upper aspect of the area in which the outer muscle layer is absent. From a" to b" no dilatation is seen. This gap acts as an effective barrier to the propagation of the peristaltic wave if it extends 30 to 40 mm. in length. A greatly diminished wave was seen once to extend caudad in which the gap was only 5 mm. Such a gap ordinarily acts as a barrier if no fluid content is within the lumen of the intestine. At a" rhythmic contractions may occur for some time before the gut musculature comes to tonic equilibrium at this point. That the two muscle layers are reciprocal elongators as peristalsis advances is evident.

sected zone with a foreshortened caudal dilatation. As soon as the constriction reaches the edge of the operated region (fig. 6) no caudal dilatation is detected. The outer coat is absent at the gap and coincident with the absence of continuity of the outer coat there is an absence of the typical caudal dilatation.


200 EBEN J. CAREY

If the outer coat is exsected for only 5 mm., an abortive continuation of peristalsis may infrequently be detected. But primarily the lack of anatomical integrity of the outer coat acted as an efficient block to the propagation of peristalsis. Frequently a rhythmic series of contractions similar to rhythmic segmentation is detected at the cephaHc aspect of the gap.

Interpretation

These two experiments prove that the anatomical continuity of the outer and inner muscular coats is necessary for the conduction of the normal peristaltic wave. When the inner coat is exsected the caudal dilatation is seen over the operated region concomitant with the cephalic constriction a few centimeters above. This proves that the inner stronger muscle is the cause of the cephalic constriction and that the caudal dilatation is due to the outer longitudinal coat.

When the outer longitudinal coat is dissected off, there is a progressive shortening of the caudal dilatation as peristalsis nears the exsected region. As the constriction nears this zone there is a progressive shortening of the caudal dilatation until it is totally absent as the constriction borders the area of operation. This confirms the conclusions reached in the first experiment.

The normal peristaltic wave is an exaggeration of the waves of rhythmic segmentation. The former presents a zone of constriction 6 to 8 cm. long in the dog's gut, whereas the latter presents constricted zones only 1 cm. long. The peristaltic wave or diastalsis has a longer constricted zone, due to the fact that a greater resistance is presented. It is the duplex contraction wave which overcomes the resistance in propelling the contents of the small intestine caudad.

On the other hand, the waves of rhythmic segmentation knead or segment the intestinal contents. A less resistance is presented, consequently a shorter constriction is found. In order that rhythmic seginentation may be effective, about 1 to 2 cm. of intestinal musculature is necessary. WTiat the determinants are that cause either the diastaltic or rhythmic waves of segmentations are not, as yet, determined.


Cannon ('12 d) found that the "normal gastric peristalsis does not require the reflex mechanism for the waves sweep from the pulsatile source to the pylorus, in an orderly manner, after the myenteric plexus has been completely interrupted by a half dozen incisions encircling the stomach." In the small intestine Cannon ('12 e) made encircling incisions through the musculosa to the submucosa, "at intervals varying between 1.5 and 2 cm. throughout the first 45 cm. of the small intestine." He found that segmentation is present in the operated region and that peristalsis is stopped.

The inference, however, that "peristalsis of the small intestine, therefore, unlike that of the stomach, is seriously interfered with by division of the myenteric plexus," Cannon ('12 f) is not to be derived from these experiments. As regards the small intestine, the intervals between the encircling incisions are too narrow for effective muscular waves of normal peristalsis. As Cannon ('12 g) observes in the cat, the trough of the wave is 4 to 5 cm. long. Those encircling incisions have intervals, the longest of which are only 2 cm. ; therefore, the musculature has been effectively put out of commission in order to manifest diastalsis, but its integrity is still intact to exhibit the shorter waves of segmentation. I repeated Cannon's experiments on the small intestine of the cat, cutting encircling incisions at intervals of 10 to 15 cm., and found that the normal peristaltic wave was present and had not been interfered with by division of the myenteric plexus.

If it is remembered that diastalsis is the wave of propulsion and that segmentation is the wave of kneading, the difference of resistance to be overcome by each is self-evident. Diastalsis needs a greater extent of the gut for effective muscular action than that of segmentation. If the anatomical continuity of the optimum extent of the gut, necessary for diastalsis is interfered with, it cannot be elicited. The integrity of the muscle was so interfered with in Cannon's experiments for effective peristaltic action.

This action was not inhibited in the stomach, due to a number of circumstances. First, the short length and greater width of the stomach compared with that of the small intestine. Second, when the musculature of the stomach contracts between the encircling incisions, a greater action is manifested on account of the greater encircHng extent of the fibers as compared with the. shorter encirchng extent of the fibers of the small intestine. Third, the reaction to muscular contraction in the stomach, therefore, is greater. The fluid contents of the stomach, consequently, will act as a medium for the propagation of the distending wave, causing a stretching and subsequent contraction of the fibers between the next neighboring encirchng incisions.

In the small intestine the lessened diameter will not allow for as great a muscular action along 2 cm. hnear extent as along a corresponding portion of the stomach. A greater extent of anatomical continuity is necessary, therefore, in the small intestine than in the stomach in order to make a similar comparison of muscular action between these two organs. By making the intervals 10 cm. between the encircling incisions in the small intestine, the peristaltic wave is not inhibited.

The difference in the power of the stomach and small intestine is readily apparent by the following brief consideration of the physical principles of the screw: The screw^ is a modification of the inclined plane, and the conditions of equihbrium are those which obtain in the case of the plane. The resistance, which is either a weight to be raised or a pressure to be exerted, acts in the direction of the vertical, and the power acts parallel to the base; hence w^e have P: R = h : 211 r; r being the radius of the cjdinder and h the pitch of the screw. (The vertical distance between any two threads of a screw measured parallel to the axis is called the pitch.)

The power is usually applied to the screw by means of a lever, as in a bookbinder's press. In the gut the power is derived by muscular contraction and the principle of the screw may be stated to be generally, the poiver of the screw is to the resistance, in the same ratio as that of the pitch of the screw is to the circumference of the apparent circle through which the power acts. This means that, other factors being equal, a greater power would be manifested in a given segment of the stomach than in a corresponding length of the small intestine because of the difference in circumference.


STRUCTURE AND FUNCTION OF S:\IALL INTESTINE 203

Reciprocal elongation of muscles

The contractile state of muscle, as well as the relaxed, arises from a power inherent in itself. The elongation or stretching superimposed on a muscle in tonic contraction depends on some extrinsic power. Simple relaxation of a contracted muscle is not sufficient to enable it to produce another requisite effect. It is necessary that there should be an elongator equal to the quantity of contraction intended to be produced. No muscle has the power of adequately extending or stretching itself; therefore, there must be an elongator. The elongators are usually muscular, but elastic tissue may serve this function as well as fluids in musculotubular organs, hke the bladder.

The reciprocal elongation of muscles is strikingly evident in the intestine. Rhythmic contraction is due to a reciprocal mechanism, each wave is composed of a contraction and an elongation of the inner spiral coat alternating with a contraction and an elongation of the outer elongated spiral or longitudinal muscle coat. At the start the contraction waves of both coats begin together, but, due to the rotary course of the inner wave and the translatory course of the outer wave, the former and stronger one will inevitably trail the latter and weaker one. The outer and inner muscles are reciprocal elongators, therefore, as peristalsis extends through the intestine (figs. 7 and 8).

When the outer and inner muscles are in normal tonic equilibrium (fig. 7) no distortion is evident. As soon as a contraction wave starts the balance is upset. The stronger cephahc constriction (fig. 8) causes an elongation of the outer muscle coat. The w^ave of the latter follows in the path of the distal region of elongation. The contraction of the outer coat causes an elongation of the inner coat in the region of the caudal dilatation. Subsequently, the contraction wave of the inner coat is seen to occupy the former zone of stretching in the region of the caudal dilatation. There is, therefore, a definite syncopation in the activity of the outer and inner muscle coats as the peristaltic wave travels through the intestine. The muscle coats act as reciprocal elongators, consequently peristalsis progresses for a variable distance through the gut instead of coming to a dead center.


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Direct observation of diastalsis

When the stomach is distended with food, a discharge of chyme into the duodenmn takes place. Upon dilatation of the pyloric constrictor there is then produced an elongation of the outer and inner muscular coat overlying the bulged area. The reaction to this stimulus of elongation is contraction. The stronger



Fig. 7 Diagram of small intestine in which the two spiral muscular layers are in tonic equilibrium.

Fig. 8 Diagram of peristaltic wave. The balance of tonicity between the inner and outer muscle layers is upset. From a' to 6' the stronger inner coat upsets the balance by causing the cephalic constriction. In the dog this trough is 6 to 8 cm. long. From b' to d' the outer coat upsets the balance by contracting. This shortens and dilates the gut. The action of the outer muscle layer acts as an effective elongator of the inner layer. This stretching stimulus puts the inner layer in a condition for immediate contraction. The outer muscle layer is put in tension caudad to d'. The contraction wave, therefore, travels progressively down the tube, due to the effective reciprocal stretching of the muscle fibers taking place distal to the contraction wave. The cephalic aspect of the tube is to the right, the caudal aspect to the left of the observer.

inner coat contracts and causes a cephalic constriction. The outer coat contracts and tends to shorten the gut forming the caudal dilatation.

The spiral structure and screw-like action of the intestinal muscles help to explain the normal direction of the peristaltic wave from above downward. Again, the fact that contraction of muscles follows in the wake of a stretching or an elongation


STRUCTURE AND FUNCTIOX OF SMALL INTESTINE 205

also acts as an effective determinant stimulus. Since the cephalic aspect of the small intestine is the first part stretched by the chjTne flowing through the pyloric valve caudad, this region will be the first to respond to the elongating stimulus by contraction.

This muscular action propels the food still further caudad. Successive areas are progressively elongated. They respond in turn by contraction. This alternation of stretching and subsequent contraction of the muscle continues on down the small intestine. The effective stimulus of elongation due to the intestinal contents together with the continuous spiral nature of the musculature readily explains the normal peristalsis as a wave progressing from above downward.

Once this direction of action is implanted in the spiral muscles, it tends always to react by screwing in the same direction as that which the food would normally take. There seems to be a physiological polarity. Every section cut from the gut tends to keep the polarity of cephalad and caudad that it originally possessed while in the intact gut. This is comparable to the analogy cited by Loeb ('12) with regard to the magnet, as follows:

If a magnet is broken into pieces, every piece has its north pole on that side which in the unbroken magnet was directed toward the north. Likewise, there are animals every piece of which produces, at either end, that organ toward which it was directed in the normal condition. We may speak in such cases of polarization."

This would explain the stasis observed by Alall ('96 d) in experiment upon the reversal of the gut. The reversed segment by maintaining the original screw-like action that it had in the intact gut would now counteract a wave of peristalsis progressing downward. This is comparable to two screws opposed in action.

There is, however, eventuallj^ a tendency for the reversed segment of the gut to become adapted to its abnormal environment. It transmits subsequently the wave of peristalsis from above downward directly opposite to that which it did previously. This reversed conveyance of food was seen by Kelling ('00), Enderlen and Hess ('01), Beer and Eggers ('07), McClure and Derge ('07).


206 EBEN J. CAREY

One fact to be emphasized finally in regard to the movement of the intestine is the left-handed screw action of the spiral musculature. A section of the pig's intestine 6 inches in length was exsected under warm saline solution. By inserting a vasehnated cotton bolus in the cephalic opening of the gut, a strong cephalic, anemic constriction is elicited. In a short time the bolus is expelled at the caudal orifice of the intestine. Inspection of the external surface of the bolus reveals a left-handed spiral arrangement of the vaseline coat. The same may be observed on a bolus of warm agar-agar or soft paraffin. The actions of the intestinal spiral muscles are, therefore, in the manner of a left-handed screw in the pig's intestine. These observations were made on the killing floor in the Cudahy abattoir. South Omaha.

The explanation of Bayliss and Starling's graphic record is schematized in figures 9, 10, 11, 12, 16, 17, 18, 19, 20, 21, 22. At each rhythmic contraction of the inner coat a contraction wave is started through the outer muscle coat. To detect the contraction waves in each muscle coat two enterographs are placed at right angles to each other. A shortening of the distance between a and h (fig. 9) is indicative of contraction in the outer layer of muscle. A shortening of the distance between c and d (fig. 9) indicates a contraction of the inner muscle coat. As the cephalic constriction progresses caudad toward the registering points, rhythmic contractions of the outer muscular layer corresponding to each contraction of the inner coat are detected in the area of caudal dilatation. This is considered by Bayhss and Starling as due to inhibitory nerve impulses which prevent contraction of the inner muscle. But it is due, however, to the contraction of the outer coat which throws the balance of tonic equilibrium between the two muscle layers in favor of the contracting outer coat, thus causing an active dilatation. This enlargement is not due to a passive relaxation or inhibition of the tonicity of the inner muscle layer. This was definitely proved in the two experiments cited above.

When the zone of cephalic constriction causes a graphic registration of the approxhnating points c and d, there is also a shortening between 6 and a. Both layers will register simultaneous



Figs. 9 to 12 These figures are explanations, based on the spiral architectonics of the intestinal muscles of Bayliss and Starling's graphic record (Journal of Physiology, 1899, vol. 24, p. 107). They state that there is synchronous activity at the same spot and at the same time of the two coats (fig. 4, Journal of Physiology, 1899, vol. 24, p. 105). Their record was produced by two enterographs placed at right angles to each other. One records the shortening between c and d. This represents contraction of the inner coat. The other records shortening between a and b. This represents contraction of the outer coat. The arrows are directed caudad to the right of the observer.

Fig. 9 This figure represents the intestinal musculature in tonic equilibrium.

Fig. 10 This figure represents a peristaltic wave produced by a stimulus. The stimulus may be a pinch, induction current, or a balloon inserted into the lumen as used by Bayliss and Starling. The inhibition of the contraction in the inner coat is due to the elongation caused by the contraction of the outer coat. The so-called inhibition is found in the zone of caudal dilation. Their records prove that the outer coat causes a widening and continues contracting. Each contraction of the outer coat corresponds to the rhythmic contraction of the cephalic constriction as it progresses caudad.

Fig. 11 The cephalic constriction as schematized has passed the upper point a.

Fig. 12 This figure represents the cephalic constriction at the points c and d. There is now produced a record of contraction of the inner coat. At the same time a record is produced of contraction of the outer coat. This is due to the point a approximating b. The record shows, therefore, simultaneous contractions, but this does not prove that the effects of the contractions occur at simultaneous points. The resultant of contraction of the outer coat is distal to that of the inner coat in the same unit of time. This is inevitable from the arrangement of the muscle fibers and objectively evident by direct and experimental observations.

207


208 EBEN J. CAKEY

contractions, but the resultant of contraction of the inner coat is a locahzed cephahc constriction, whereas, in the same unit of time the resultant of contraction of the outer coat is a caudal or distal dilatation. These resultants Bayliss and Starling failed to take into account.

At each rhythmic contraction of the inner close spiral musculature, a smiultaneous contraction takes place in the outer muscle layer. The wave of contraction in the outer coat will continue to travel down the intestine. With the next successive and progressive contraction of the inner muscle a second simultaneous wave of contraction is sent through the outer layer. A third, a fourth wave, and so on, are successively started, but the consecutive intervals between the advancing contractions of the outer coat are foreshortened. This leads to a summation of contractions resulting in the caudal dilatation.

This zone of caudal dilatation is produced by manifold contraction waves of the outer coat. Each wave of contraction is immediately preceded by a zone of stretching or tension. Into these elongated areas the trailing contractions take place. The stretching or elongation of the outer is produced by contraction of the inner coat. The latter causes elongation of the intestine and at the same time stretching of the outer muscle coat.

The duplex contraction phenomenon, of a cephahc constriction and caudal dilatation, is due to the structural arrangement of the outer and inner muscular coats of the intestine. A stimulus will start a contraction wave in each simultaneously. The contraction wave travehng in the inner coat in a rotary manner will inevitably trail that of the outer coat pursuing a translatory course. This is comparable to an electric current traveling in a straight wire from a to b and the same intensity of current traveling in a spirally coiled wire through the same linear distance. It is at once evident that it would take longer for the latter current to reach the same destination on account of the greater distance traveled in a rotary direction as compared to the shorter linear distance traversed by the former.

This analogy may be directly applied to the two contraction waves involved in any type of muscular movement of the in


STRUCTURE AND FUNCTION OF SMALL INTESTINE


209



Figs. 13 to 15 These figures are diagrams of successive waves of rhythmic contraction. They illustrate the reciprocal elongation of the muscle coats in contraction. Rhythmic contraction is based upon the arrangement of the muscular fasciculi.

Fig. 13 This figure depicts in a reconstruction the alternate contractions and dilatations of two successive rhythmic waves. At the point a there is a dilatation simultaneously with contraction at the point b. This wave continues on in like manner through the points c and d, and through the points e and /. The successive wave is shown by the broken curved lines.

Fig. 14 This figure represents the isolated first wave extending progressively caudad, as depicted in figure 13 as continuous curved lines.

Fig. 15 This figure represents the second or successive isolated wave shown in broken curved lines in figure 13. It is evident that the contraction at the point a, figure 15, occurs in the location previously stretched or dilated in figure 14, point a. This tj'pe of segmentation is produced by successive contraction waves extending through the gut. When the outer muscle coat contracts there is a thickening of the fibers on the proximal side (cephalic aspect) of the area of dilatation. At the same time there is a stretching or elongation of the fibers on the distal side (caudal aspect) of the area of dilatation. This is represented by a thickening and attenuation of the outer lines, respectively. When the outer muscle coat contracts, the resultant shortening and dilatation also elongate the inner muscle coat. Thus, the deformation produced is due to the upsetting of the equilibrium of the two muscle layers by contraction of the outer coat. This stretching stimulus applied to the inner coat results in contraction. The contraction wave progresses into the next stretched zone, and so on down the gut. Rhythmic contraction and diastalsis, therefore, are actions based on the definitive structural plan of the musculature. The effective manifestation of either one or the other of these two actions depends upon the efficient reciprocal elongation of the two sets of intestinal muscles. This is experimentally proved by dissecting off either one or the other of the two layers. An effective block to the propagation of the normal waves is at once established.



Fig. 16 This figure is taken from Bayliss and Starling's ('99) (Journal of Physiology, vol. 24, p. 107, fig. 5) enterographic record of the simultaneous contractions of the outer and inner muscle coats of the intestine. Their interpretation of the record is as follows: "At the beginning of the observation the intestinal wall was contracting rhythmically, the contractions affecting both coats, and being synchronous in both. At (A) a bolus made of cotton-wool coated with vaseline was inserted by an opening into the intestine 4| inches above the enterographs. It will be seen that the contractions of the circular coat cease instantly and this inhibition is accompanied by a gradually increasing relaxation. There is some relaxation of the longitudinal coat, but the rhythmic contractions do not altogether cease. On inspecting the intestine it was seen that the introduction of the bolus caused the appearance of a strong constriction above it. This constriction passed downwards, driving the bolus in front of it. The numbers above the tracing of the circular fibers indicate the distance of the bolus in inches from the uppermost enterograph lever. At (B) the bolus had arrived at the upper longitudinal lever and at (C) had passed this and was directly under the transverse enterograph, or a little below it. At this point a strong tonic contraction of both coats occurs, expelling the bolus beyond the levers. This strong contraction passes off to be succeeded by another, which like the first is moving down the intestine. In this second tonic wave the rhythmic contractions are evident, superposed on the curve. After the passage of the bolus there is a shortening of the gut (increased tone of longitudinal fibers)."

According to the interpretation of the writer, the 'inhibition' or 'gradually increasing relaxation' seen in the record from a to c, upon insertion of the bolus above, represents a gradually increasing tension or stretching of both layers as the cephalic constriction nears the contraction record beginning at C Immediately preceding each contraction of the outer layer there is a zone of tension into which each wave of contraction enters. The caudal dilatation, therefore, is a summation of advancing contraction waves closely following one another. This is objectively evident in the curve for the outer layer, L, from a to c, in which rhythmic contractions are taking place. Immediately preceding each contraction is a zone of stretched muscle fibers, the sum of which would tend to lengthen slightly the caudal dilatation over that of the same length of intestinal musculature either in tonic equilibrium or in rhythmic segmentation. The more rapid rhythmic contractions and increased stretching of the outer layer throw the balance of equilibrium between the outer and inner layers in favor of the former. The inner layer in the area of caudal dilatation is held, therefore, in a state of gradually increasing tension or stretching until the optimum at the point c is reached. At the point c both layers record contraction waves, but it must be remembered

210


STRUCTURE AND FUNCTION OF SMALL INTESTINE 211

testine. The contraction wave traveling in a rotary manner in the inner close spiral muscle will trail the contraction wave traveling in the outer elongated spiral muscle. The former and stronger contraction will cause a cephalic constriction, the latter and weaker contraction will cause a caudal dilatation (figs. 7 and 8).

The fasciculi of the inner coat make one complete turn in every 0.5 to 1 mm., whereas those of the outer coat make one complete turn in every 200 to 500 mm. Consequently, if we consider the fasciculi as not interconnecting, which they do, however, we will find that a contraction wave that travels 5 mm. in a linear direction through the inner coiled muscle coat will find its complimentary contraction wave that started at the same time and place in the outer coat to have traveled approximately 300 mm. in a translatory direction. This estimate is based on an intestine 25 mm. in diameter (figs. 18, 19, 20, 21). The intestinal movements are rhythmic, however, and this characteristic is due to waves transmitted in each coat at each duplex contraction, thereby causing a reciprocal elongation and mutual coordination of the two waves characterizing peristalsis or segmentation (figs. 13, 14, 15).

that these contraction waves at any period of observation occupy areas of former tension. The tension of the inner coat is caused by the outer one and the tension of the outer coat is caused by the inner one. The double phenomenon of tension prior to contraction travels quickly down the intestine in the outer coat. The relationship of prior tension and trailing contraction is comparable to a gymnast climbing a rope. The tensed rope in advance corresponds to the zone of tension in the intestinal musculature and the progressing gymnast represents the advancing contraction wave.

The graphic record also strikingly shows that the waves travel in a translatory direction much faster in the outer than in the inner muscle layer due to the rotary direction of the path in the latter. The record shows that seven waves in the outer coat have passed the recording point before the inner wave of contraction has reached the point b. This fact is also verified after the main rhythmic tonic waves of diastalsis have passed the recording levers at d and e (d and e were inserted by the writer). The intestinal muscles are now tending to equilibrium and have not reached as yet the state in which each contraction of the outer and inner coats show the simultaneous contraction curves prior to the insertion of the bolus. L, contraction curve of outer fibers. C, contraction curve of inner fibers. Contractions recorded by down strokes of enterographic lever, relaxations by upward movement of lever.


t/pper


Fig. 17 This figure represents the position of the enterographs which were placed at right angles to one another in Bayliss and Starling's experiment (Journ. Physiol., vol. 24, p. 107, fig. 5a) a and 6 are the levers of the enterograph recording the contractions of the inner muscle coat.



Figs. IS to 21 These figures represent the initial progressively increasing caudal dilatation synchronous with successive contractions of the inner coat cephalad.

Fig. 18 This figure shows contraction of the inner coat from a to 6 simultaneous with the contraction of the outer coat through one-half the distance from a' to 6'. The contraction wave of the outer and inner coats are preceded by zones of tension or stretching of the muscle fibers produced by the reciprocal elongating actions of the two muscle layers.

Fig. 19 This figure represents the contractive wave of the inner coat advancing from 6 to c synchronous with an increasing caudal dilatation produced by the outer coat midway between a' , b' to c'.

Fig. 20 This figure depicts the caudal dilatation still further advanced from b' to d' at the same time that the inner constriction travels from c to d.

Fig. 21 This figure demonstrates the advancing contraction wave of the inner coat occupying the distance from d to e. The caudal dilatation extends from a point midway between b', c' to e'. With each successive rhythmic constriction produced by the cephalic contraction wave in the inner muscle fibers a corresponding wave is initiated in the outer muscle layer. The summation of the contraction waves in the outer group of fibers produces the caudal dilatation due to the greater activity of these fibers over that in the inner layer. The balance or equilibrium is upset, therefore, in favor of the outer fibers at this point.

212


STRUCTURE AND FUNCTION OF SMALL INTESTINE 213


R^ZT.


Fig. 22 This figure is a diagram representing the differential rates of translatory advance of the successive contraction waves in the outer and inner layers of muscle fibers. Line a represents the inner close spiral muscle fibers. Lines 6, c, d, and e, the outer elongated spiral muscle layer. Upon stimulation there is produced a rapid caudal dilatation and a slowly produced cephalic constriction. Contraction waves begin simultaneously, in both coats, but, due to the linear course followed by that in the outer muscle layer, a difference in time takes place before the effects of contraction are objectively evident in the two layers of muscles. When the cephalic constriction advances from I io 2 line a, the caudal dilatation is evident from 7' to ^' line 6. When the cephalic constriction progresses still further from ;? to S line a, the caudal dilatation is a summation of two contraction waves in the outer fibers from 2' to S' line h, and 1" to 2" line c. Likewise with continuation of the constriction produced by the inner coat from 4 to 5 line a, the caudal dilatation is a summation of four consecutive waves closely following one another, namely, 4' to 5' line h, 3" to 4" line c, 2'" to 3'" line d, and 1"" to 2"" line e. From this it is evident that the degree of caudal dilatation is directly proportional to the extent of the cephalic constriction. If the cephalic constriction is a long trough of 5 cm. or more, the summation of caudal constrictions in the outer fibers is greater than if only 1 cm. is involved in the formation of the cephalic constriction. This explains the difference of extent of the caudal dilatation manifested in the intestinal movement of segmentation and diastalsis.

Conclusions The Screw-like Action of the Small Intestine

1. Because of the left-handed, heUcoidal arrangement of the musculature of the intestine, the intestinal movements are comparable to the action of a left-handed screw.

2. The fascicuh of the inner coat make one complete turn in every 0.5 to 1 mm., whereas those of the outer coat make one complete turn in every 200 to 500 mm. Consequently, if we consider the fasciculi as not interconnecting, which they do, however, we will find that a contraction wave that travels 5 mm. in a linear direction through the inner coiled muscle coat will find its complimentary contraction wave that started at the same time and place in the outer coat to have traveled ap


214 EBEN J. CAREY

proximately 300 mm. in a translatory direction. This estimate is based on an intestine 25 m.m. in diameter.

3. The inner muscular layer is wound as a close spiral. The outer as an open spiral. The difference in rate of translatonj progression of the two contraction loaves depends upon this muscular arrangement. The ivave traveling in the inner group of fibers takes a rotary course, whereas that in the outer fibers takes a more translatory course to reach a corresponding destination. Therefore, the contraction of the stronger inner muscle coat will inevitably trail that of the outer. The arrangement of the intestinal muscle layers clearly explains the phenomeiion of cephalic constriction and caudal dilatation of diastalsis without invoking the aid of hypothetical nerve paths. Peristalsis, therefore, is a duplex contraction phenomenon produced by the differential rate of translatory advance of the two contraction waves in the outer and inner muscle layers, respectively.

4. By exseetion of the inner muscular layer of the intestine, it is proved that the caudal dilatation of diastalsis is produced primarily by the summation of contractions in the outer layer of muscle fibers.

5. By exseetion of the outer muscular layer, it is proved that the cephalic constriction is caused by the inner layer of closespiral fibers.

6. The movements of the intestine depend upon the reciprocal elongating actions of the outer and inner layers of muscle fibers, respectively. These movements are superimposed on the tonic condition of equilibrium of the two muscle layers. The application of any drug, therefore, that decreases the excitability of the musculature or destroys the tonic equilibrium of the two layers will indirectly effect the typical muscular responses.


STRUCTUEE AND FUNCTION OF SMALL INTESTINE 215

LITERATURE CITED The helicoidal architectonics of the small intestine

Caret, Eben J., J. of Gen. Physiol., 1919-20 (a) vol. 2, p. 357; (b) vol. 3, p. 61; (c) Anat. Rec, 1920, vol. 19, p. 199.

GooDSiR, John 1868 Anatomical Memoirs, edited by William Turner. Edinburgh, vol. 1, p. 367.

Mall, F. P. 1896 Johns Hopkins Hospital Report, vol. 1, p. 60.

Screw-like intestinal movement

Bayliss, W. M., and Starling, E. H. 1899 Journal of Physiology, vol. 24,

(a) 107, (b) 142, (c) 114, (d) 115. Beer, E., and Eggers, F. 1907 Annals of Surgery, vol. 46, p. 582. Cannon, W. B., American Journal of Physiology, 1912, vol. 30, (a) 127, (b)

1912, vol. 30, 127, (c) 1902, vol. 6, 252, (d) 1912, vol. 30, 118, (e) 1912,

vol. 30, 122, (f) 1912, vol. 30, 122, (g) 1912, vol. 30, 124. Enderlen, H., and Hess, G. 1901 Deutsche Zeitschrift fiir Chirugie, Bd. 59,

S. 240. Englemann, A. 1871 Archiv fiir die gesammte Physiologic, Bd. 4, S. 35. Kelling, H. 1900 Archiv fiir klinische Chirugie, Bd. 62, S. 326. LoEB, Jacques 1912 The mechanistic conception of life. Univ. of Chicago

Press, 92. LtTDERiTZ, F. 1889 Archiv flir pathologische Anatomie, Physiologie, und klinische Medicin, Bd. 98, S. 33. Magnus, G. 1904 Archiv fiir die gesammte Physiologie, Bd. 103, S. 531, 536;

Ergebnisse der Physiologie, 1905, Bd. 7, S. 45. Mall, F. P. 1896 Johns Hopkins Hospital Reports, vol. 1, (a) 74, (b) 125,

(c) 85, (d) 93. McClure, C. W., and Derge, J. D. 1907 Johns Hopkins Hospital Bulletin,

vol. 18, p. 473. Nothnagel, W. 1882 Archiv fiir pathologische Anatomie, Physiologie, und

klinische Medicin, vol. 88, p. 4.


Resumen por el autor, Naohide Yatsu.

Sobre los cambios de los organos reproductores en la parabiosis heterosexual de ratas albinas.

En las parabiosis de macho y hembra (individuos unidos mediante una operacion quirurgica), algunos de los foliculos de Graaf se desarrollan normalmente y forman cuerpos amarillos, mientras que la mayoria experimenta cambios regresivos. En estas parabiosis el utero no se modifica de modo marcado, aun cuando puede presentarse una hiperplasia de la subserosa. Los foliculos ovaricos de las parabiosis de macho y hembra castrado no se desarrollan normalmente, ni tampoco se forman cuerpos amarillos. Los quistes foliculares y los cuerpos atreticos son 'abundantes. Hay un aumento aparente de las celulas intersticiales, entre las cuales existen unas cuantas celulas luteinicas. El utero es el 6rgano mas afectado mediante la union con un macho castrado. Especialmente clara es la producci6n de hidrometrias. El testiculo y la prostata no son afectados por la uni6n con hembras normales o esteriles.

Translation by Jos6 F. Nonidez Cornell Medical College, Xew York


author's abstract of this paper issued by the bibliographic service, mat 9


ON THE CHANGES IN THE REPRODUCTIVE ORGANS

IN HETEROSEXUAL PARABIOSIS OF

ALBINO RATS^

NAOHIDE YATSU Anatomical Institute, Keio Universitxj

SEVEN FIGURES

The actions of products from various endocrine organs have been studied of late so extensively that one can hardly keep in touch with the literature relating to even a single organ. Of the methods employed for such investigations parabiosis has not so far been used as it ought to be. And, I think, much new hght will be thrown in the future upon endocrinology by making use of this method.

In the fall of 1916, several series of experiments in joining together two albino rats of different sexes were begun at the Zoological Institute of the Imperial University, with the help of Mr. Masanosuke Takesita.^ The object of these experiments was to obtain evidence regarding the effects of male and female hormones in mixed condition upon united individuals. The present investigation was more immediately suggested by Lillie's paper on the theory of the free-martin which appeared in "Science" ('16). In this paper he expresses the view that in the heterosexual twins of cattle the reproductive organs of the female fetus are impaired by the influence of sexual hormones from the male fetus, provided a blood circulation has been established

1 In carrying out the experiments described in this paper, I am indebted to the Tokugawa Memorial Fund.

■ Mr. Takesita's death took place rather suddenly in November of 1919, just after the operative part of the present investigation came to an end. He graduated from the Imperial University in 1916. At the time of his death he was thirty years old. I owe a great deal to his skill and intelligence in carrying out this study.

217


218 NAOHIDE YATSU

between the two. I thought it would be interesting to see how the male hormones act upon the female and vice versa in adult heterosexual parabiosis.

As to the method of parabiotic operation I am indebted not a little to Dr. Rikuro Matsuyama. His kindly advice was invaluable. When I began this work he was engaged in a study of uraemia produced by extirpating the kidneys from one component of rat parabioses. Later, however, he directed his attention to the hne which I was following. He obtained results almost the same as mine, and pubhshed an excellent paper in Japanese in August, 1919. Yet, since his paper is written in a language only shghtly intelligible to our confreres outside this country and because of the existence of discrepancies in our work and of additional observations, the publication of the present paper may not be regarded as superfluous.

Alost of the rats used for the experiments were bred in the laboratory. Their ages, body length and body weight were noted at the time of operation (parabiosis and gonadectomj^) and when killed. All the parabiotic pairs from which the material was taken had been healthy. It is, therefore, almost certain that any alteration found in the preparations is due to the action of mixed hormones produced by united individuals.

MALE-FEMALE PARABIOSES

I have twenty-four successful cases of male-female parabioses. The period of union ranges from 11 to 179 days. It need hardly be mentioned that the actual parabiotic period does not correspond with that of union for the blood circulation becomes established between two animals only after at least ten days. The 5'oungest animal operated on was twenty-nine days old and the oldest ninety days old. The individuals used for parabiosis were in some cases from the same htter and in others from different litters, but in all cases they were of the same age.


CHANGES IN REPRODUCTIVE ORGANS — ALBINO RATS 219

1. Changes in the ovary

The ovaries of parabiotic paii's were cut into sections and compared with those of unoperated females at corresponding ages, which had been kept separated from the males.

At the outset it might be mentioned that the time of appearance of the first corpus luteum, that is, the first ovulation comes at about the same time in the ordinary females and in the parabiotic females. Ovulation may continue for a considerable length of time, as is indicated in a case (161-day-old female, 111 daj^s in parabiotic union) in which several apparently normal eggs at the metaphase of the second maturation mitosis were found in the oviduct. And this is also substantiated by the fact that both ^Morpurgo ('08) and ^latsuyama '19) obtained normallj'^ developed fetuses from parabiotic females.

^Miile the formation of the corpora lutea is taking place on the one hand, a great many graafian follicles are found undergoing regressive changes on the other. In fact, many more folHcles degenerate in the ovaries of parabiotic females than in ordinary females. This I do not hesitate in attributing to the influence of the male component. Predominance of degenerating follicles makes itself evident after thirty days' union with the male. The longer the parabiotic period, the larger the number of degenerating follicles. It may also be added that the regressive changes set in more in younger folHcles than older ones.

There are several modes of degeneration of the folHcles. But it is important to note that none of the modes is pecuHar to parabiosis. The onh^ difference found between those in the normal ovary and in that of parabioses is in degree of change.

The first indication of degeneration of the folHcle is the dissolution of the cells composing the cumulus oophorus. First the egg is set free in the follicular cavit}^ Then it is divided or rather fragmented into five or six cells of different sizes in the manner described by Hennuguy ('94) in the rat and by Spuler ('01) in the guinea-pig. Sometimes there are two nuclei in one ceH. These 'blastomeres' disintegrate in the folHcular fluid so completel}'^ that no trace of them can be found. The above changes also take place in very young folHcles.

THE ANATOMICAL RECOHD, VOL. 21, NO. i


220 XAOHIDE YATSU

Pari passu with the dissolution of the egg goes the disintegration of the stratum granulosum. This is accompHshed in two ways. The first mode is the gradual dissolution of the component cells from the inside, reducing the laj-er to a very thin sheet of cells, often separated from the theca interna by a narrow space. In an advanced stage, this layer is fenestrated, appearing in sections as an interrupted ring. The other means of destruction is by phagocytes that have entered the follicle from without. Whence they come I am not able to ascertain. At any rate, thek,phagocytes are much larger than the granulosum cells and


j? (tf ©»0C ,*a? ^


7f,'^o


O. ^. 4?/ *^ >^4'


i£i^#i/-ii;^^


Fig. 1 Portion of a degenerating follicle (forty-seven days of parabiotic union). P., phagocytes; G.-st., granulosum; /., theca interna; E., theca externa. X560.

are readily detected by ingested debris. They migrate toward the follicular cavity until they occupy a position in the fluid, as is shown in figure 1. As to the fate of these cells, I am unable to offer any suggestion. It is very probable that they also disintegrate in the folhcular fluid.

As the granulosum layer disappears, the theca interna increases in thickness. Sometimes this process goes on only in a restricted area, sometimes along the entire layer. In either case the cells constituting the theca interna increase in size. These cells however, are quite different from the lutein cells. The nucleus and the cell body of the former are much smaller, more granular, and stain more deeply with haematoxyHn than those of the latter.


CHANGES IN REPRODUCTIVE ORGANS — ALBINO RATS


221


The cytoplasm of the lutein cells is more eosinophilic. In cases where the central cavity is obliterated, a corpus atreticum composed of modified theca interna cells is formed.

Side by side with the above-described atretic follicles are found those with the theca cells modified into the lutein cells. Such follicles have often a large central cavity. Matsuyama thinks that this tyi^e is peculiar to the ovaries of parabioses, but in my sections of the ovaries of old females this kind of follicle is not uncommon.

A feature that may rightly be called characteristic of the ovaries of parabiosis is the enormous growth of the interstitial cells.



Fig. 2 Portion of ovary showing six groups of interstitial cells (forty-seven days of parabiotic union). X 86.

Matsuyama has noticed this peculiar change also. This is met with especially in the female, which is operated upon when young; that is, at a stage in which the folHcles have not yet attained their full size.

It cannot be doubted that the interstitial cells are modified theca cells. Consequently, the folhcular cavity is found, in most cases, inside the mass of these cells and in some cases degenerating ova and debris of the granulosum layer, as is shown in figure 2.

The lutein cells are sometimes found among the interstitial cells. They can readily be distinguished, since the former have large nuclei and a single nucleolus in each, while the latter


222 XAOHIDE YATSU

have small nuclei, with scattered chromatin granules. Is the formation of lutein cells clue to immigration or transformation? I think both processes may go on, judging from the fact that few mitotic figm-es are met with.

In conclusion it may be said that in parabiosis the male exerts a certain deteriorating effect upon a good many graafian follicles of various stages, though some of the folHcles remain apparently normal and are able to discharge fecundable eggs. The injurious effect of the male hormones does not produce anything peculiar to parabiosis, but accelerates degeneration processes that would take place in normal ovaries

2. Changes in the uterus

The changes in the uterus of the parabiotic female are usually not so marked as those in the ovary. As a matter of fact, changes, if any, are so shght that they do not at all affect the normal development of the fetuses, as was shown by the cases of INIorpurgo and jMatsuyama.

In some females, however, changes are noticeable after a month of parabiotic union. The hyperplasia of the stratum subserosum is the main feature. The uterine glands decrease in number. The muscular layers become thinner. The eosinophile leucocytes seem to be more abundant than in the normal uterus.

It is interesting to note that in two cases the uteri have been modified exactlj^ like those of female + castrated male parabioses, which will be described in the next section. In the two cases the testes were smaller than in other males of parabiotic union, though spermatogenesis was going on normally.^

3 In one of the two males (139 days old when killed, 93 daj's of parabiotic union, body weight 160 grams, body length 182 mm.) the right testis was 0.977 gram and the left .0.967. In the other male (159 days old when killed, 106 days of parabiotic union, body weight 195 grams, body length 170 mm.) the right testis was 0.338 gram and the left 0.310 gram. In comparison it may be stated that in the males of similar age and of similar length of parabiotic period the testes weigh between 1.100 and 1.200 grams.


CliANGES IN REPRODUCTIVE ORGANS — ALBINO RATS 223

FEMALE + CASTRATED MALE PARABIOSES*

J\lales were castrated, and after various intervals they were united with females. I have fourteen successful cases of this kind of parabioses. The period of union ranges from 18 to 179 days.

Contrary to what one might expect, the changes in the ovary and the uterus are more marked in these cases than in the abovedescribed female + uncastrated male parabioses.

1. Changes in the ovary

The 0Y2ivy is so affected by the influence of the castrated male that it ceases to discharge the eggs, judging from the fact that no normal corpora lutea are formed and what look like them are nothing more than the corpora atretica. All the folhcles undergo regressive changes of one kind or another. The processes of degeneration are dilTerent in follicles of different stages of development. They are- the same as those described by Boshagen ('04), Benthin ('11), Cohn ('09), and others. It may here be mentioned that none of the regressive changes is pecuUar to this kind of parabiosis, all being met with in the normal ovar}^ as is the case with male-female parabioses. But all the modifications come in intensified form.

Of several modes of change of the follicles, T may mention first of all a most striking one, which T would not hesitate to regard as characteristic of this type of parabiosis. This is cyst formation due to enormous growth of the stratum granulosum. One example is shown in figure 3. Here one sees uneven growth of this layer. As the folhcular fluid accumulates the follicle is distended, reducing the wall to extreme thinness. Sometimes the blood-vessels make their way into the cumulus oophorus. The egg in the folhcular cysts usually undergoes degeneration without fragmenting. It may occasionally divide, but as far as I know it does not act as in younger follicles.

Harms (11) has described a case of this kind of parabiosis in Rana temporaria, but I am not able to learn from his paper how the female organs were affected by the castrated male.


224 NAOHIDE YATSU

This remarkable growth of the glanulosuni layer takes place not long after parabiotic operation. Indeed, I have a case in which the ovary showed this change only eighteen days after union.

At one portion of the foUicular cyst one often sees an accumulation of the lutein cells formed from the theca interna. I have no strong evidence to oppose the view that this represents a stage on the way to formation of a corpus atreticum. But I am rather inclined to beheve that any follicle once distended on the way to become cystic, will remain as such and never transform into the solid corpus atreticum. As a matter of fact lutein cells are found in the wall of half -grown follicles. This is represented in figure 4. Here the lutein cells are formed not only from the



Fig. 3 Stratum granulosum of a follicle (thirty days of parabiotic union). X86.

theca interna directly, but also from the interstitial cells. After the disintegration of the granulosum cells of such folUcles they turn into solid corpora atticare though sometimes a small cavity appears in them.

Other changes, such as unusual growth of the interstitial cells, are exactly the same as in male-female parabioses.

2. Changes in the uterus

The uterus, of all the female organs I have examined, is the most afTected by the union with a castrated male. The striking change makes itself evident as early as eighteen days after parabiotic operation. The normal structure of the uterus will not here be described, since that has been so fully studied by Po


CHANGES IN REPRODUCTIVE ORGANS — ALBINO RATS 225

wierza ('12) in the mouse and by Belling ('06) in the rat. The first indication of the change is the rapid growth of the mucous layer. This is soon followed by the accumulation of turbid fluid in the uterine cavity. The subserosa or vascular layer, with not a few eosinophils, becomes thinner. The uterine glands may remain for some time compressed within the now narrow


?—: ;-A^





Fig. 4 Part of a follicle showing invasion of lutein cells into st. granulosum (G.) from interstitial cells (In.) (107 days of parabiotic union). I., theca interna; E., theca externa. X 186.

subserosa. Finally they disappear completely. The longitudinal muscles are no longer found. The diameter of this distended uterus is 6 mm., while that of the normal one is not more than H nim. The wall is reduced to one-tenth the normal thickness. This hydrometral condition is not accompanied by hydrosalpinx, which Fischel obtained experimentally ('14). No noticeable changes take place in the tubal part.


226


NAOHIDE YATSU TESTES or PARABIOSES


The testes of male-female parabioses (twenty-fom- cases from 11 to 179 days) and of male+spayed female parabioses (eleven cases from 6 to 148 days) were weighed and cut into sections.

It is interesting to note that the histologic structm-e of the testes is not affected at all by the union with either unoperated





f'Zf -Y •( nr!-'nn



Fig. 5 Section of normal (A) and distended uterus (B). X 4.5.

Fig. 6 Portion of distended uterus (eighteen days of parabiotic union). Notice the remnant of longitudinal muscle fibers. X 420.

Fig. 7 Portion of half-distended uterus (twenty-three days of parabiotic union). Here one notices a uterine gland to the right. X 97.


CHANGES IN REPRODUCTIVE ORGANS — ALBINO RATS 227

or spayed female. In the latter combination, however, the sperm formation is somewhat delaj^ed. In one case the spermatozoa could not be seen in a ninety-eight day rat joined for thirty-two days with a spayed female.

RESULTS

That the spermatozoa are functional in male-female parabioses is shown b}^ the fact that a female which had been kept with a male-female parabioses gave birth to a litter. Copulation took place in this case 134 to 135 days after parabiotic operation.

In passing it may be mentioned that the prostate is not affected at all by the union with either normal or spayed female. In castrated male-female parabioses the prostate atrophies as in the solitary castrated male.

1. In male-female parabioses some graafian follicles undergo the normal course of growth and the corpora lutea are formed, while a large majority of follicles undergo regressive changes. None of the changes is pecuUar to this kind of parabiosis.

2. In male-female parabioses the uterus is not modified very markedly. Sometimes hj^Derplasia of the subserosa is noticed.

3. In the ovary of castrated male-female parabioses none of the folhcles develops normally. No corpora lutea are formed. Follicular cysts and corpora atretica are abundantly produced. Noticeable growth of the interstitial cells takes place and sometimes the lutein cells are met with in the interstitial cell gi'oups.

4. The uterus is most affected by the union with a castrated male. Hydrometra of various grades is the remarkable feature. The uterine tubes are normal.

5. The testis is not affected at all by the union with either normal or spayed females. The same is true of the prostate.

COMMENT

From the above-described parabiotic experiments rather unexpected results were obtained. One would naturally suppose that the female organs would be more affected by the male with the testes. But as a matter of fact they are more influenced


228 NAOHIDE YATSU

by the castrated male. To account for this phenomenon I think it is very probable that the endocrine organs of the male are affected by castration, and that the ovarj' and uterus of united individuals are in turn influenced by the hormone or hormones produced from these organs. But what organ partakes in this process and how I do not know.

It is also interesting to note that the testis is not impaired in the least by the ovarj^ of the female to which it is un ted.

Anatomical Institute, Keio University, July 22, 1920

LITERATURE CITED

Beiling, K. 1909 Beitrage zur makro- und mikroskopischen Anatomie der

Vagina und des Uterus der Saugetiere: Am. m. A., Bd. 67. Bexthin, W. 1906 Uber Follikelatresie in Saugetiereovarien: Arch. f. Gyn.,

Bd. 87. BosHAGEN, A. 1904 iJber die verschiedenen Formen der Riickbildungspro dukte der Eierstockfollikel: Zeit. f. Geburthilfe u. Gyn., Bd. 53. CoHN, F. 1909 Uber das Corpus luteum und den atretischen FoUikel des Mens chen und deren cystische Derivate: Arch. f. Gyn., Bd. 87. FiscHEL, A. 1914 Zur normalen Anatomie und Physiologie der weiblichen

Geschlechtsorganen von Mus decumanus, sowie iiber die ex per.

Eezeugung von Hydro- und Pyrosalpinx. Arch. f. Entm., Bd. 39. Harms, W. 1911 Uber den Einfluss des Kastrierten auf den normalen (Kompo nenten bei Parabiose von Rana: SB. d. Gesell. z. Ford. d. gesamm.

Naturwiss. Marburg, Bd. 2. Henneguy, L. F. 1894 Recherches sur I'atresie des follicules de Graaf chez

les mammiferes ct quelques autres vertebres: Journ. Anat. et. de la

physiol. LiLLiE, F. R. 1916 The theories of the free-martin. Science, vol. 63. Matsuyama, R. 1919 Parabiose wo oyoseru Zikkentekikenkyil II. Xissin Igaku (Japanese). MoRPURGO, E. 1908 Uber Parabiose von Siiugetieren verschiedenen Gesch lechtes: Miinch. med. Wochensch., Bd. 47. Powierza, St. 1912 Uber .4nderungen im Bau der Ausfiihrungsgange der

Mjiuse wiihrend ihres postembryonalen Lebens: Bull. d. Acad. Cracovie. Spuler, a. 1901 Uber die Teilungserscheinungen der Zellen in degenerier.

FoUikcln des Saugetierovariunis: Anat. Hefte, Bd. 14.


r ^


Resumen por el autor, Howard Homer Bell.

Diverticulos del duodeno. Descripci6n de tres observaciones.

El primer caso estudiado presentaba un diverticulo en la regi6n de la ampolla de Vater. El segundo presentaba un diverticulo en la regi6n de la ampolla mencionada y otro mas inferior en la segunda parte del duodeno; ambos pacientes eran varones y marcadamente obesos. Su edad era cuarenta y dos, y sesenta y un aiios, respectivamente. El tercer caso presentaba tres diverticulos, uno en la papila mayor, otro en la menor y un tercero en la uni6n de la segunda y tercera parte del duodeno. El paciente era una hembra emaciada de setenta y cinco anos de edad. Diverticulos semej antes se presentan tambien en el colon. En todos los casos estudiados la muscularis terminaba bruscamente sin formar parte del saco. Estos diverticulos se consideran como adquiridos a consecuencia de la existencia de puntos debiles en la muscularis.

Translation by Jos6 F. Nonidez Cornell Medical College, New York


AOTHOR'S ABSTRACT OF THIS PAPER ISSUED BT THE BIBLIOGRAPHIC SERVICE, MARCH 28


DIVERTICULA OF THE DUODENUM

HOWARD H. BELL

Pathological Laboratory, Washington University School of Medicine, St. Louis,

Missouri

TWO FIGURES

Diverticula have been observed in all divisions of the gastrointestinal tract. Particular attention, however, is given to diverticula of the duodenum on account of their relation to the common bile and pancreatic ducts and associated organs.

Diverticula of the alimentary tract occur most frequently in the colon, ileum, oesophagus, pharynx, duodenum, and stomach, — in the order named (Buschi).i Baldwin- observed fifteen cases of duodenal diverticulum in 105 cadavers. Schiippel (quoted by Baldwin) found seven instances in forty-five bodies, and later at Kiel found one in 200 bodies. Linsmayer^ observed forty-five cases in a study of 1367 autopsies.

Davis* found from a study of the literature that 16 per cent of duodenal diverticula occurred in subjects under fifty years, 37 per cent betw^een fifty and sixty years, and 47 per cent above sixty years. In the series studied by Linsmayer, the youngest showing diverticulum was thirty-six years and another thirtyeight years old. Three instances occurred between forty and forty-nine years, 5 between fifty and fifty-nine years, 13 between sixty and sixty-nine years, 14 between seventy and seventynine years and 4 between eighty and eighty-seven years. Wilkie^

1 Virchow's Arch. f. path. Anat., 1911 (206), 121.

2 Anat. Rec, vol. 5, 1911, p. 121.

3 Verhandl. d. deutsch. path, gesellsch. 17, 445, 1914.

Tr. Chicago Path. Soc, vol. 9, 1913, p. 1. Edinburgh Med. Jour., vol. 11, 1913, p. 219. 229


230 HOWARD H, BELL

found that in twenty-six cases, seventeen were in males and nine were in females. He believes that diverticula of the duodenum are congenital in origin and bases this belief upon the following data :

1. "The duodenum in the course of normal development gives off hepatic and pancreatic buds; consequently developmental anomalies might be expected to occur more frequently' in this than in other regions of the intestinal tract. Tandler ('02) found that congenital atresia occurs in the duodenum 39.6 times as frequently as in any other segment of small intestine of equal length.

2. "The observation of Lewis and Thyng ('08) showed that during early foetal life, diverticula are often met with in the the upper reaches of the small intestines, particularly in the duodenum.

3. "An accessory pancreas is occasionally observed in or on the wall of such diverticulum.

4. "The case reported by Shaw, where in a newborn infant there were found both a diverticulum and a congenital occlusion of duodenum.

5. "In the cases recorded by Letulle ('98) and Falconer ('07) congenital diverticula of the oesophagus and stomach, respectively, accompanied the duodenal diverticula.

6. "Many of these diverticula abut on and even indent the head of the pancreas."

More than 400 diverticula were observed in the gastro-intestinal tract of an adult male (Hansemann*'). These were situated along the line of attachment of the mesentery corresponding to the points of penetration of the larger vessels, particularly the veins. This relationship of vessels to diverticula has not infrequently been observed. Relaxation of venous sheaths in association with circulatory stasis (Graser^), fatty degeneration of the muscularis, (Roth^), and fatty infiltration of the intestinal

« Virchow's Arch. f. path. Anat., 1896, Bd. 144, S. 400.

' Munchcn. med. Wchnschr., No. 22, 1899, S. 721.

8 Virchow's Arch. f. path. Anat., 1872, Bd. 56, S. 197.


DIVERTICULA OF THE DUODENUM 231

wall (Aschoff^) were conspicuous in certain cases and considered as the causes of the diverticula.

Baldwin found from the literature that the muscularis was observed in the walls of these diverticula in twenty instances, while in sixteen it was absent. In forty-seven cases there was no report on this subject. (Keith^") states that it is not uncommon to find in old people in the posterior wall of the duodenum near the termination of the common bile duct diverticula which are pouches of mucous membrane extruded at weak points in the musculature. However, he cites the cases described by Clogg and Thompson as instances of developmental diverticula; these occurred in the small intestine below the duodenum in association with accessory pancreas, and possessed the muscular coats of the intestine.

The arrangement of the muscularis is subject to great variation and aids very little in a study of the etiology of these diverticula. Meckel's diverticulum possesses the musculature of the intestinal tract. Its origin is peculiar and suggests no explanation of diverticula elsewhere.

In most instances diverticula of the duodenum were found at necropsy and had no direct relation with the cause of death. However, in a case reported by Bauer, ^^ biliary stasis with jaundice was caused by inflammation of a diverticulum at the site of the ampulla of Vater. Death followed intrathoracic hemorrhage. Furthermore, several instances of duodenal diverticula occurred in association with pain in the upper abdomen and disturbances of digestion; either duodenal ulcer or gall-bladder disease was found in this group of cases, which possibly accounted for the symptoms present. However, disturbance of digestion, poor nutrition, and certain nervous manifestations have occurred in association with duodenal diverticula, which were found by x-ray examination or at operation, symptoms that could not be

9 Pathologische Anatomie, dritte Auflage, zweites Band, S. 824: Jena, Gustav Fischer, 1903.

10 Brit. Med. Jour., 1910, p. 376.

" Wiec, klin. Wchnschr., 1912, (25) 879.


232 HOWARD H. BELL

explained otherwise than by the diverticula. A diverticulum has led to surgical intervention or has been found at operation and corrected in several instances. Consideration of the facts presented in the literature indicates that the significance of the associated symptoms is uncertain.

I have examined two specimens of diverticulum of the duodenum. The first instance occurred in a teamster, forty-two years old, who related no symptoms indicating that this diverticulum had given him any trouble. He was very obese. Death followed failure of cardiac compensation associated with aortic stenosis and chronic fibrous myocarditis. The anatomical diagnosis made at necropsy was as follows :

Aortic stenosis and insufficiency; hypertrophy and dilatation of heart; recent and old infarcts of lung; chronic passive congestion of all organs; chronic tuberculous process of lung and spleen; nephrohthiasis; obesity; diverticulum of duodenum.

The diverticulum occurred as a blind pocket immediately above and anterior to the major papilla. It communicated with the duodenum through a puckered opening measuring 0.5 cm. in diameter. It was about 2 cm. deep and 1 cm. wide. It extended to the left and shghtly upward anterior to the common bile and pancreatic ducts in the fissure between the lobes of the head of the pancreas. The common bile duct was slightly dilated and opened independently into the duodenum beside the pancreatic duct, being separated from it by a very narrow septum. The sac was formed by thinned intestinal wall. No vessels were found which penetrated the sac. The situation of this diverticulum is shown in figure 1 .

Sections were made from the wall of the diverticulum. The muscularis ended fairly abruptly and did not form a part of the sac. Considerable fat was deposited in the intestinal wall and some occurred in the muscularis.

The second instance occurred in a man sixty-one years old and showed two diverticula. No symptoms referable to the diverticula were recorded. The patient had been employed in an organ factory. He was very obese and suffered from a long-standing irreducible inguinal hernia. The hernia was


DIVERTICULA OF THE DUODENUM


233


reduced and repaired by operation. The caecum, which was greatly dilated and distended, filled the sac. The patient died a few days following the operation, from peritonitis associated with many ulcers and numerous perforations of the caecum, ascending and transverse colon. The anatomical diagnosis made at necropsy was as follows :

Operative incisions in right thigh and inguinal regions ; repair of hernia with fascia transplantation; peritonitis following intestinal ulceration and perforation; follicular enteritis; chronic fibrous myocarditis; arterial sclerosis; focal sclerosis of endo



Fig. 1 Drawing showing the inside and lateral views of the duodenum and the relation of the diverticulum to the openings of the common bile and pancreatic ducts.

cardium, aortic and mitral valves; chronic diffuse nephritis with atrophy of cortex and fatty degeneration of pyramids; chronic passive congestion of viscera; chronic bronchitis; fatty degeneration of liver and kidneys; chronic obliterative appendicitis, prostatic hypertrophy; healed tuberculosis of peribronchial lymph nodes; old pleural adhesions; obesity; lipomatosis of pancreas with fat necrosis; diverticula of duodenum; patent foramen oval; accessory spleen.

The first diverticulum occurred at the site of the ampulla of Vater. It communicated with the duodenum through an oval opening measuring about 1 cm. vertically and 0.6 cm. horizontally.


234


HOWARD H. BELL


It was about 2 cm. deep and terminated as a blind pocket. The diverticulum extended to the left and slightly upward in front of the common bile and pancreatic ducts in the fissure separating the two lobes of the head of the pancreas. The common bile duct was moderately dilated and opened into the posterior and lower part of the diverticulum, about 0.5 cm. from the intestinal wall, in conjunction with the pancreatic duct. The sac was formed throughout by thinned intestinal wall.



Fig. 2 Drawing showing the inside and lateral views of the duodenum and the relation of the diverticula to the duodenum and the common bile and pancreatic ducts.

The second and larger diverticulum occurred in the lowest part of the duodenum along the posterior surface and rested chiefly upon the vena cava. It was disc shaped, being flattened anteroposteriorly. It communicated with the duodenum through an opening 0.9 cm. in diameter. After fixation the sac measured 3 cm. in its longest dimension and 1.5 cm. in its shortest. It was about 2 cm. deep. The sac was formed by thinned intestinal wall. The anatomical relations of these diverticula are shown in figure 2.

Sections from the walls of the diverticula show that the muscularis ended rather abruptly and did not form a part of the sac.


DIVERTICULA OF THE DUODENUM 235

Considerable fat was deposited in the intestinal wall and some occurred in the muscularis.

The two cases herein reported show some of the conditions frequentl}" observed in association with duodenal diverticula. The patients were male and moderately advanced in life, i.e., fortj-two and fifty-one years old, respectively. Each showed much venous stasis. Obesity was marked in both instances. The muscularis ended rather abruptly about the openings and did not form a part of the walls of these diverticula.

A consideration of the facts presented in the literature and of the cases reported here leads one to the conclusion that duodenal diverticula of this type are not congenital, but acquired, occurring at points in the muscularis which are weakened by the passage of ducts and blood-vessels or by pathological processes, and that increasing age and the greater muscular activity in men are factors in their production.

SUPPLEMENTARY REPORT

I have recently studied a specimen, with three diverticula of the duodenum, removed at autopsy.

The patient was a woman seventy-five years old, and was markedly emaciated. No symptoms referable to the diverticula were recorded. There was general arterio-sclerosis with gangrene of the feet. Death followed acute parotitis and micrococcus aureus was grown from the parotid gland and the heart's blood.

The anatomical diagnosis w^as as follow^s: General arteriosclerosis; gangrene of the feet; acute parotitis; volvulus of the caecum and transverse colon; carcinoma of cervix uteri with extension and metastasis; chronic nephritis with small contracted kidney; healed calcified tubercles in the lungs, bronchial lymph nodes and spleen; diverticula of the duodenum and colon; chronic interstitial pancreatitis; periportal cirrhosis of the liver.

The largest diverticulum occurred at the junction of the second with the third part of the duodenum, along the upper border, 22 mm. below the major papilla. It was saccular in shape and extended upward, inward and backward. The opening was


236 HOWARD H. BELL

oval, measuring 15 mm. by 8 mm.; the longer axis was paralled with the folds of mucous membrane which at that point extended obliquely downward and outward. The sac measured 18 mm. deep. A small artery and vein crossed the outer wall of the sac and entered the intestinal wall at the base of the pouch.

The second diverticulum occurred immediately to the right of the bile papilla and extended upwards, outward and backward along the right side of the common bile duct. Its opening was a crescentic shaped slit which encircled the outer half of the ampulla. The common bile duct and the pancreatic duct opened independently into the duodenum; there was no ampulla of Vater. The diverticulum was saccular in shape and measured 15 mm. deep. It was empty, but pressure upon the gall bladder filled it with bile. A transverse fold of the mucous membrane hung down over the bile papilla and the opening of the diverticulum. No vessels were observed in the walls of this diverticulum.

The third diverticulum occurred immediately above the minor papilla. It was conical in shape and embedded in pancreatic tissue along the duct. It measured 8 mm. at the opening and 12 mm. deep. It was situated 18 mm. above the major papilla. A transverse fold of mucous membrane hung downward over it.

The muscularis ended abruptly at the opening of these diverticula and did not form a part of the sacs. The walls were represented by mucous membrane and muscularis mucosae.

The muscularis of the intestinal tract near the diverticula and at some distance from them was thin and showed considerable fatty degeneration. Fat was deposited in fine droplets throughout many muscle fibers. Sections were treated with potassium bichromate after the method of Bell,^- to fix the fat, and paraffine sections were stained with Sharlach R.

The small diverticula of the transverse colon were likewise protrusions of the mucous membrane through the muscularis. No special relationship of blood vessels to these diverticula was established.

It is of interest to note the presence of marked chronic interstitial pancreatitis and slight periportal cirrhosis of the liver in

'2 Bell, E. T., Jour. Path, and Bacteriology, vol. 19, 1914, p. 105.


DIVERTICULA OF THE DUODENUM 237

association with the diverticulum at the major papilla. Distention of this diverticulum would have exerted pressure on the common bile duct and pancreatic duct. Much significance, however, cannot be attached to this relation in view of the associated generalized sclerosis.

The two upper diverticula of the last case were obscured by folds of mucous membrane and were found only after special search was made. It seems probable that closer observation would show that diverticula of the duodenum occur more frequently than former observations have suggested.


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Resumen por G. Carl Huber, por el autor Tanzo Yoshinaga.

Contribuci6n al estudio del desarroUo temprano del coraz6n de

los mamiferos, con especial menci6n del del

conejillo de Indias.

Las observaciones publicadas en el presente trabajo se basan en el estudio de una serie de estados muy pr6ximos en el desarroUo de los embriones del conejillo de Indias, cortados en serie de 5 a lO/z de espesor, tanto en el piano sagital como en el transverso. Los estados estudiados comprenden el periodo de desarroUo desde el duodecimo al decimo-quinto dia despues de la inseminaci6n, o sea desde el momento en que aparecen por primera vez los angioblastos en la regi6n mds tarde ocupada por el coraz6n hasta el estado de corazon en forma de S. Los estados muy pr6ximos han sido reconstruidos en placas de cera mediante el metodo de Born, y el estado mas joven presenta el comienzo de la formaci6n del espacio pericardico.

Las pruebas obtenidas mediante este estudio son interpretadas por el autor como una demostraci6n de que los angioblastos que han de formar el futuro coraz6n tubular endotelial derivan independientemente del mesodermo de la esplancnopleura. El esbozo de los pliegues miocardicos y su desarrollo progresivo son objeto de una discusion por parte del autor, quien presenta su desarrollo en una serie de figuras basadas en reconstrucciones.

Translation by Jos6 F. Nonidez Cornell Medical College, New York


A contribution to the early development of the heart in mammalia, with special reference to the guinea-pig

Yoshinaga T. A contribution to the early development of the heart in mammalia, with special reference to the guinea pig. (1921) Anat. Rec. 21(3): 239-308.

Tanzo Yoshinaga

Department of Anatomy, University of Michigan

Twenty-Three Figures

Introduction

Since the fundamental investigations on the development of the heart in mammals by His, Born, and others were published, many prominent investigators have contributed to our knowledge concerning the earlier stages of development of the heart and of the pericardial cavity in representatives of almost all classes of vertebrates. The earlier workers began their investigations after the developmental stage in which the embryonal heart tube had already assumed the complete S form. From the results of their work, however, only very general conclusions can be drawn. In many important details the literature shows contradictions, while each theory advanced has been supported by investigators of recognized ability.

The following work was undertaken at the suggestion of Professor Huber. I take this opportunity to express my hearty thanks to him for the use of his collection, which he placed at my disposal, and for his invaluable help. This work concerns itself chiefly with the origin of the endothelial tubes, the early development of the pericardial cavity, and the mode of confluence of the bilateral myocardial tubes, written with the hope of contributing something of interest to the early development of the heart.

The material for this study was obtained from many uninterrupted series of embryos of the guinea pig, from the embryological collection in the Department of Anatomy of the University of Michigan, prepared by Professor Huber. The great majority of the embryos were fixed in Carnoy's fluid and all were cut into either cross or sagittal series at either 5^ or 7^ thickness, also a few at lOju thickness.

In a study of the development of the endothehal and the myocardial tubes and of the pericardial cavity, to show their successive developmental changes and their relative topographical relations, a number of models were prepared according to Bom's method of wax-plate reconstruction. These were made at a magnification of 300 diameters, with the aid of the projection apparatus, by superimposing the drawings of every section of the cranial part of the embryo. The thickness of the wax plates was changed in proportion to that of the sections from 1.5 to 2.1 and 3 mm., respectively. All the models described here are deposited in the Department of Anatomy at the University of Michigan.

All the figures of the sections presented here were drawn at relatively high magnifications with the aid of the camera lucida and subsequently reduced to the proper size in reproduction. The figures of the models were prepared according to the method described by Doctor Atwell. I am grateful to Doctor Guild and to Mr. Smith for help in preparing the wax plates.

LITERATURE REVIEW

Before considering the material studied in this investigation, I wish to refer to some of the theories held by earlier writers. I do not wish to give a complete resume of the historical developments, but rather briefly to indicate the representative opinions directly concerning the subject.

In the embryonic shield of mammals at first there are present two pairs of longitudinal vessels, one of them situated near the middle line on the entoderm on each side representing the supraintestinal longitudinal blood vessels, and the others are found primarily on the entoderm approaching the lateral margins of the embryonic shield and these representing the subintestinal longitudinal blood vessels. In the cephalic portion of these latter the heart is formed, the walls of these vascular anlagen being peculiarly dilated and thickened. From this ontogenetical standpoint, the early development of the heart is merely a part of the development of the intra-embryonic vascular system.

In the survey of the literature on the subject of the origin of the intra-embryonic blood vessels in mammals, the theories held by the earlier investigators, and still maintained, can be divided into three categories.

The first theory was advanced by His, who made his observations of the flat embryonic shield of the chick. Hertwig, Kolliker, and others supported this theory. According to the Einwachsungslehre of His, with which the theory of the parablast was first connected, the early blood vessels of the embryonic shield are formed by a sprouting or ingrowth of the preexisting endothelial lining of the blood vessels, which had previously developed in the extraembryonic vascular area. The ingrowth of the blood-vessel anlagen into the embryonic area takes place as solid, tenuous sprouts of the cells, which are primarily found to be anastomosed with each other, to form a close network in the area pellucida.

These sprouts of cells enter into the embryonic area through the space between the splanchnopleure and entoderm, until they reach the somitic region, where they anastomose and become canahzed to form hollow vessels. Ultimately, this network of the endothelial lining forms the dorsal aortae, uniting in a longitudinal direction. The ingrowth of the endothelial sprouts is not limited to the somitic portion, but takes place also in the cranial part, entering from the lateral margin of the embryonic shield, through the space between the splanchnopleure and the entoderm, until they reach the heart anlage, where they develop the endocardium. The endothelial sprouts spread out, forming the ventral aortae and the blood vessels of the cranial region. The former blood vessels will be connected with the dorsal aortae which are prolonged cranialward by the sprouting and in the same way by turning over of the blind end of the pharynx ventral ward.

Ttirsting studied the development of the aortae in the rabbit and confirmed the conclusion of His, namely, that these vessels are formed by a longitudinal anastomosis of the ingrown endothelial sprouts, derived from the extra embryonic area, through the space between the splanchnopleure and the entoderm. He noticed the early connection of the dorsal aortae with the vitelline plexus.

Vialleton and Evans studied the development of the intraembryonic blood vessels in birds and came to the conclusion that in birds the greater part of the descending aortae is developed by a conversion into a continuation of the aortae of the innermost strand of the capillary plexus, extended into the embrj-onic shield from the neighboring yolk sac.

Lewis investigated the intraembryonic blood vessels in rabbits from eight and one-half to thirteen days after insemination, and claims that from the network of vessels in the splanchnopleure of the yolk sac all intraembryonic vessels are apparently derived as offshoots. The network ends mesially in two aortae. With the formation of the pharynx, this net is so folded as to produce dorsal and ventral aortae with the connecting first aortic arch.

Bremer recently repeated the investigation of the same material and came to practically the same results. His summary is given as follows: In the rabbit, the dorsal aorta, the first aortic arch, the conus arteriosus, and the lateral heart are all parts of an original network of angioblast cords, derived from the extraembryonic plexus" of blood vessels. Those portions of the network which are mechanically favored in their position persist, the other portions disappear. Although dealing in this paper with the development as found in rabbit embryos, I have examined various other species, as the chick, pig, sheep, etc., and feel satisfied that in all essential points the story of the development of these primary vessels in other vertebrates will be found similar to that here described."

Many other investigators support this theory, while still others do not accept it. Ranvier seems to think that the Einwachsungslehre of His must be regarded as a simple hy]oothesis, and states: "Mais il est clair qu'aucum embryologiste n'a pu suivre ce developpement continu par bourgeonnement dans le corps neme de I'embryon; c'est laune simple hypotese. "

The second theory of embryonic vasculogenesis was first advanced by Rabl, who asserts that the first aortic arch in amphibia is formed by the accretion and extension of the endothehal cells proliferated in the paired heart rudiments, when these endothelial tubes were developed. Moreover, he applies this possibility to other blood vessels of the embryo, in which they are formed by the extension of the preexisting endothehal cells, as, for instance, can be seen in the regeneration of the capillaries. His statement reads as follows : " Die Beobachtung, dass bei den Amphibien die ersten Aorten Bogen durch Auswachsen des Endothelsiickchen entstehen, legt uns aber noch die Frage nach, ob es vielleicht auch das Endothel aller anderen Gefiisse in letzter Instanz auf die Zellen des Endothel-sackchens zuruckzufiihren sei, mit anderen Worten ob nicht vielleicht all Gefasse in derselben oder in ahnlicher Weisse entstehen, wie die Capillaren. "

Furthermore, in his later work, The Theory of the Mesoderm, " he repeated his assertion: Ich habe die erste Entwickelung der Gefasse namentlich an den Aorten wiederholt genau verfolgt, und ist mir kein Fall erinnerlich, der mich an der Ueberzeugung irre gemacht hatte, dass neue Endothelen immer nur aus bereits bestehenden ihren Ursprung nehmen."

Riickert investigated the early development in the eggs of selachians, in which at first the subintestinal veins can be seen in the anterior embryonic shield. Here the endothehal cells are produced from the ventral angles of the lateral plates, detaching as free angioblasts, which subsequently assume forms of the cellular groups or chains between the splanchnopleure and entoderm. With regard to the anlage of the aortae in the anterior part of the embryonic shield, Riickert assumes still further that their origin is in loco and that here are anticipated the adjacent mesodermal somites, subordinately the dorsal wall of the gut comes under consideration.

P. Mayer discovered the transverse blood vessels in the eggs of the torpedo, connecting the subintestinal veins with the aortae, and he attributed their origin to the emigrated cells from the ventral parts of the mesoderm, wandering along the gut wall dorsalward. Riickert agreed with the opinion of Mayer. In the vascular development of the embryo he claimed that the angioblasts still arise in loco, for example, the blood vessels of the pronephros from the visceral walls of the somite. The angioblasts of the mandibular blood vessels from the visceral plate of the second cranial somite as well as from the wall of the foregut.

Raffaele, Emmert, and others have accepted the local formation of the embryonic blood vessels and are in agreement with the idea of Rlickert. After the first publication of his work in 1888, Riickert investigated all classes of vertebrates and confirms his claims to the local formation of the embryonic blood vessels. Concerning the development of the chick, he expressed himself as follows: So findet also beim Huhn statt des Einwachsen der Gefassanlagen eine von der Peripherie des Keimwalles gegen den Embryo zu fortschreitende Differenzierung- derselben aus dem Mesoderm statt, was mit den Beobachtungen an Selachieren iibereinstimmt, Auch innerhalb des Embryo entstehen beim Huhn die Gefassanlagen durch locale Ausschaltung des Zellen Materials aus dem ]\Iesoblast, wo von ich mich bei der Herz so wie der Aortenbildung iiberzeugt habe. "

Mollier reached the same conclusion, confirming Rlickert. After thoroughly studying the material of a wide scope, he concludes as follows: Es lasst sich also fiir die Genese der embryonalen Gefasse der Amnioten zur Zeit ein Urteil dahin fassen, dass die Lehre von der localen Entstehung der Gefasszellen auch hier Geltung besitzt und dass die von His und Vailleton gegebenen Fliichenbilder, ferner die Rekonstruktionsbilder von Turstig in dem Sinne zu deuten Sind, dass die im Embryo sichtbaren ersten Gefasszellenstriinge nicht als Sprossen ausserembryonaler Gefassanlagen entstanden sind, sondern vielmehr ihre Entstehung aus einzelnen, in loco entstandenen und netzformig vereinigten Gefasszellen nehmen."

Sobatta not only supported the theory of Mayer and Rlickert, but he also emphasized that those blood vessels found on the walls of the yolk sac were derived from the intraembryonic blood vessels as a result of their continuous outgrowth.

New light was shed on this contradictory evidence by a number of investigators who employed the methods of experimental embryology and were able to show that the yolk-sac angioblasts may be kept out of communication with the intraembryonic blood vessels, thus lending evidence in favor of the local formation of the embryonal blood vessels.

The mechanical separation of the vessels of these two portions was employed by Graper, Hahn, Miller and Mc\Miorter. These workers have obtained endothelium on both sides of the chick embryo, in which one side was severed from the extraembryonic blastoderm. A further strengthening of the theory of the local formation is found in the recent experimental work by Reagan, who writes as follows: "In conclusion it is well to consider the following recently established facts which should share in defining our morphological interpretation. The yolk sac is not necessarily the site of formation of the earliest blood vessels. Intraembryonic blood vessels develop in situ when communication of the extraembryonic vessels with intraembryonic tissues is prevented by chemical or mechanical means."

The method of exposing the developing embryo to diluted anesthetics was employed by Stockard, who claimed as a result of his work that in Fundulus embryos the heart endothelium and the aorta arise in loco within the embryo, as the blood vessels, even the mesoderm are absent in the yolk sac in the cranial portion.

Among the investigators who have accepted the local formation of the intraembryonic blood vessels, opinions are still quite divergent at present as to from what part of the embryonal blastoderm the angioblasts are differentiated. I shall not again thoroughly discuss this point, as I have already done so in my previous paper on this subject. But I shall add that there are many authors who consider the origin of the angioblasts in mammals as derived from the entoderm. Martin figures a cross-section of a cat embryo 2 mm. long and in his prominent " Lehrbuch der Anatomic der Haustiere" states: Wahrend man liber die erste Entwickelung der Blutgefasse im Embryonalleib noch nicht im Klaren ist, kennt man die Bildung der peripheren Gefasse genau. Ihrer Abstammung nach sind die Innenwand (endothelium) auch der embryonalen Gefasse wie die des Herzens entodermaler Natur, wahrend die iibrige Wand vom Mesoderm geliefert wird. Ich finde bei Katze die erste gefassbildenden Zellen und Zellgruppen eininnigsten Zusammenhand mit dem Entoderm desDarmes, ja so gar schon rundliche Spaltildungen in Entoderm selbst. Auch die ausserembryonalen Blutgefasse sind nach Rabl entodermalen Ursprungs. " In the figure depicted by Martin, angioblasts can be seen, connected with both the mesoderm and the entoderm.

In the study of a perameles embryo of 6.08 mm. in length, Miss Parker says with regard to the origin of the endothehal cells : " The evidence of this stage does not justify any definite statement with regard to the origin of the endothehum of the heart. " And, moreover, she adds, that in an earher stage the appearance by no means excludes the possibility of the entodermal origin of the endothelium.

After investigating the origin of the endothelial and blood cells in the embryo of the ferret, Wang comes to the following conclusion: The facts revealed by the study of the early stages in the development of the ferret point to the conclusion that, whilst blood cells and vascular endothelium are closely related to each other and are formed invariably between the mesoderm and entoderm, there is evidence to show that, in the ferret, the origins of these two vascular elements are separate and distinct — the blood cells arising from the entoderm and the vascular endothelium from the mesoderm."

"If the biphyletic origin of the blood cells and vascular endothelium is to be accepted, two more points still remain to be solved, namely, how, when, and where the first blood cells enter the circulation. Unfortunately, the ferret embryos, at present worked upon, provide no definite evidence on this point, but it is quite clear that angioblast cells are formed outside the embryonic area, and that blood vessels are formed inside the embryonic area, and are at first devoid of blood corpuscles. "

AVe shall now briefly review the data concerning the mode of the fusion of the bilateral heart anlagen; there are many divergent opinions.

Since Hensen first declared that in mammals the heart anlage is bilateral, one on each side of the embryo not far from the midsagittal plane and on the ventral aspect of the pericardial cavity, it was long believed that these two lateral heart anlagen ultimately came in contact and fused together in the middle ventral surface of the embryonic shield, forming a single secondary heart tube. Even though the secondary fusion of the bilateral endothelial tubes is universally acknowledged, there are many contradictory theories concerning the formation of the single myocardial heart anlage together with the mode of fusion of the bilateral primitive pericardial cavity. In his work on comparative embryology, Balfour thus speaks: In mammals the two tubes out of which the heart is formed, appear at the sides of the cephalic plates, opposite the region of the mid and hind brain. They arise at a time when the lateral folds which form the ventral walls of the heart, are only just becoming visible. On the formation of the lateral folds of the splanchnic walls, the two halves of the heart become carried inwards and downwards, and eventually meet on the ventral side of the throat. For a short time they here remain distinct, but soon coalesce into a single tube. "

Minot writes: "In mammals b}^ the bending down of the layers and the expansion of the coelom the vorderdarm is shut off and the lateral heart anlagen are brought together in the median line below the vorderdarm, and there fuse into a single thick tubular wall around the double endothelial heart ; it is not long, however, before the endotheUal tubes also fuse into one. As in the chick the two mesothelia, when the median heart arises, form a membrane (mesocardium) by which the heart is attached to the tissue above and below; both mesocardial membranes break through, putting the two coelematic cavities into communication and leaving the tubular heart suspended by its ends. "

The theory of the fusion of the lateral folds of the splanchnic walls, enclosed within the laterally placed pericardial cavities at the ventral side of the foregut in mammals, as in amphibia or birds, as many investigators have asserted and now believe, is supported by the following authorities: Balfour ('81), Strahl and Carius C89)^ Tandler ('12), Wilson ('14), Bryce ('08), Minot ('92) Bailey ('12), Schultze ('15), Dandy ('10), Martin ('02), and Arey (' 17) . From this it would seem that, as many of the above named authors claim, the heart must be provided, at least temporarily, with a ventral and a dorsal mesocardium.


In a similar way in his valuable work on the first heart anlage. MoUier says: "Das Mesocard, ventral oder medial gelegen, ist dem dorsalen der Anamnier zu vergleichen. Ein dem ventralen entsprechendes kann erst nach dem zusammenstossen beider Pleuro-pericardialhohlenwande gebildet werden. Beim Meerschweinchen hingegen liegen die ersten Herzzellenstrange lateral von den Firsten der Darmfalten, und sie werden durch den Darmschluss gar nicht unter die ventrale Darmwand verlagert, wie beim Kaninchen, sondern riicken, zwischendorsalerand ventraler Mesocardfalte gelegen, einander naher, bis zur Beruhrung und endlich Verschmelzung. Doch erfolgt auch hier, wie aus der Figur ersichhch, der Durchbruch des ventralem Herzgekroses zuerst."

Robinson has pointed out that the formation of the foregut is mainly attributed to the unproportionately rapid development of the embryo over the relatively stationary line between the embryonal and extraembryonal areas. If the idea were true, that lateral folds of the mesoderm converge ventrally until their entodermal covering has met together in the ventral middle line and both lateral pericardial cavities have fused together beneath the ventral walls of the foregut, then the heart is not only attached by the dorsal mesocardium to the foregut, but also by the ventral mesocardium to the ventral wall of the body. However, Robinson denies this generally accepted idea and the existence of the ventral mesocardium absolutely, at any time in the development of mammals, and he applies this fact to support his theory, that the separation of the foregut from the yolk sac is not due to the tenaciously held process of the tucking in of the margins of the embryonic area, but to the fact that the relatively slow-growing margin is demarcated between the embryonic and extraembryonic portions of the wall of the ovum, which rapidly increase their their extent, expanding over the boundary margin. According to him, in mammals, the pericardial mesoderm is present in the pericardial portion of the embryonic area, and it is completely separated into somatic and splanchnic layers before the head fold appears. There is therefore a single pericardial cavity which extends from side to side along the anterior boundary of the embryonic shield. As the head fold is formed, the pericardial region is reversed and it is carried into the ventral wall of the foregut, where it is present as a U-shaped tube, which communicates with the general coelom at each end. The rudiments of the heart are formed in the splanchnic layer of the pericardial mesoderm. Therefore, after the reversal of the pericardial area, they He on the dorsal wall of the pericardial cavity, attached to the ventral wall of the foregut by the dorsal mesocardium.

Prior to Robinson, Ravn pointed out the correlation between the formation of the foregut and the forward growth of the embryonic shield. He also thoroughly described the mode of reversal in the primitive pericardial cavity.

On the other hand, many investigators believe that an active backward progression of the foregut opening occurs, in addition to the forward growth of the head fold. They deny the actual fusion of the lateral mesodermal folds in the ventral middle line. Rouviere agrees with Robinson as to the absence of the ventral mesocardium in mammals, while he does not dismiss the meaning of the forward growth of the head fold on the formation of the foregut. According to his account, in a rabbit embryo of 201 hours, both the pericardial cavities (les deux cavities parietales) show the separated bilateral canal on each side, which has grown forward around the anterior end of the head fold and become fused together from a single continuous cavity in the embryo of 207 hours. The splanchnopleure forming the caudal wall of the pericardial cavity assumes a continuous fold, which Tourneux designated as the cardiac fold (repli cardiaque) and which he considered as growing backward automatically as a whole. As the free edge of the splanchnopleural fold has progressed always in advance of the primordial heart, no fusion of the splanchnopleure is involved and also no ventral mesocardium is formed.

In a description of the growing processes in the developing chick embryo, having kept them under direct observation while still ahve, Graper asserts that there is considerable evidence in support of the view that the margin of the foregut (Darmpforte) moves caudally, concurrently, with the forward growth of the head fold. Moreover, he marked out diagrammatically the mode of the backw^ard progress of the foregut opening and a quite different manner of the closure of the foregut than that of the medullary canal.

Uskow also claims the automatic backward progress of the foregut opening, according to the increase of the pericardial cavity.

In her study of the early stages in the development of marsupials, Miss Parker declares that the forward growth of the head fold doubtless plays an important part in the initiation of the formation of the foregut and that the actual backward growth of the foregut opening, but not the fusion of the lateral folds, brings about the lengthening of the foregut.

In the study of the early development of the heart and cranial blood vessels in ferret embryos, Wang agrees with Miss Parker in the absence of the ventral mesocardium, there being no fusion of this part of the pleuropericardial wall, nor that any part of the gut closure is effected by the fusion of the lateral folds.

Observations

Stage I

The material for this stage consists of many specimens removed from the uterus of the guinea pig thirteen days and twelve hours or fourteen days and eleven hours, respectively, after insemination. Some of them were cut longitudinally and the others transversely.

A. The first embryonic shield which came under consideration, was removed from the uterus thirteen days and twelve hours after insemination and was in a cross-section having a 7 ^ thickness; 233 sections fell to the embryonic shield. The head fold had not begun to develop. The shallow neural groove was present on the surface of the embryo. The primitive streak was well developed and terminated caudally in a shallow notched groove. The mesoderm was thickened in the caudal part of the embryonic area and indicated the allantoic mesoderm. In the notochord there was present the chordal canal at its caudal end, but in other parts it was spread out to form a chordal plate through dehiscence of the ventral wall. The caudal end of the notochord was fused with an area of ectodermal proliferation at the cranial end of the primitive streak.


In the mesoderm there was observed no evidence of mesodermic somites nor could the coelomic cavity be detected. The mesoderm consisted of two lateral wings on each side in the cross-section, separated completely in the middle line by the notochord, except in the cephalad end of the embryonic shield and in the region of the primitive streak. In the cranial end of the embryonic shield, that is, the part distal to the future pharyngeal membrane, in which the ectoderm and entoderm were coalesced, the lateral wings of the mesoderm were fused, continuing caudally into the lateral wings, but sharply terminated against the extraembryonic area cranially and laterally. In this portion of the mesoderm, namely, in the pericephalic mesoderm, it formed a thinner layer than anywhere else. In the primitive streak a large mass of undifferentiated mesodermal cells was fused with both lateral wings, obUterating the demarcation between the mesoderm and ectoderm. In the mesoderm two layers of the 'cell band could not be distinguished; the dorsal surface of the mesoderm was, in general, compact, its outhne was clearcut; here the spindle-shaped nuclei had a relatively regular arrangement.

Between the dorsal surface of the mesoderm and ectoderm, as well as between the ventral surface of the mesoderm and entoderm, there could be distinguished clear intervals, which could be attributed in large measm^e to shrinkage. The mesodermal cells were spread out in two or three layers and were spindle-shaped and connected wdth each other by short protoplasmic processes. In the ventral surface of the mesoderm a loosening of the cell band could be seen, characterized by an increased distance between the respective nuclei. Intercellular spaces became more distinct and wider, the spindle-shaped nuclei had no definite arrangement. In nearly all sections there could be demonstrated some free, isolated cells, detached from the cell band of the mesoderm, lying between the ventral surface of the mesoderm and entoderm, as shown in figure 1. According to His, these cells are identical with the angioblasts. In some sections the angioblasts are connected with the indented ventral margin of the mesoderm by broad protoplasmic bridges; in some other sections the protoplasmic bridges are narrow, the cells are distinctly pedunculated; in still other sections they are joined to the mesoderm by faint fibrils. Frequently a mitotic figure can be recognized in the mesodermal cells, adjacent to the angioblasts. These findings show that there can be no doubt of a distinct proUferative activity of the mesodermal cells; furthermore, every transitional feature of the migration or the detachment of the mesodermal cells, which apparently are destined to become anigioblasts, point out the fact that these angioblasts have originated in the ventral surface of the mesoderm.

Figure 1 was reproduced from the forty-ninth section, counting from the cephalic border of the embryonic shield, and

LEGEND LETTERS FOR ALL THE FIGURES

A., atrium F.G.O., foregut opening

Am., amnion I. M.S., intermesocardial space

Aug., angioblast L.P.C., lateral pericardial cavity

Ao., aorta M.C., myocardial cavity

A.V.C., atrioventricular constriction Mes., mesoderm

A.V.Ca., atrioventricular canal M.G., medullary groove

B., bulbus cordis M.T., myocardial tube

B.V.C., bulboventricular constriction A^., notochord

C.M.L., craniomedian limb of the peri- P., pericardium

cardial cavity P.C., pericardial cavity

Co., coelom P.M., pharyngeal membrane

D.M., dorsal mesocardium P. P. P., pleuropericardial passage

D.W.P., dorsal wall of pericardium S.A.C., sino-atrial constriction

Eel., ectoderm Som., somatopleure

End., endothelium Spl., splanchnopleure

Ent., entoderm S.R., septum ridge

E.O., endothelial offshoot S.V., sinus venosus

E.T., endothelial tube T.A., truncus arteriosus

F.G., foregut V.W.F., ventral wall of the foregut

Fig. 1 The 49th section of a series of 233 cross-sections of 7 m thickness of an embryonic shield of the guinea pig, removed 13 days 12 hours after insemination. The early stage of the formation of the angioblasts from the ventral surface of the mesoderm. X 150.

Fig. 2 The 41st section of a series of 237 cross-sections having a 7 m thickness, removed from the uterus of a guinea pig 14 days 11 hours after insemination. The ventral surface of the mesoderm becomes loosened and angioblasts are separated. X 150,



Fig. 3 The 40tli setion of a series of 162 sagittal sections having a 7 ^i thickness. This embryonic shield was removed from the uterus of a guinea pig 13 days 12 hours after insemination. The angioblasts form the cell strands between the splanchopleura and entoderm. X 150.

Fig. 4 The 63rd section of a series of 300 cross-section of 7 m thickness of an embryonic shield of a guinea pig, removed 13 days 11 hours after insemination. In the lateral plate of mesoderm the discontinuous coelom is present. X 150.


corresponds approximately to the future hindbrain region, in which region endotheUal tubes had been differentiated from the angioblasts in the next stage. As the contour of the entoderm is distinctl}^ demarcated from these cells in our specimens, as the figure shows, it may be excluded from direct participation in the formation of these cells,

B. The next embryonic shield selected for discussion was removed from the uterus of a guinea-pig fourteen days and eleven hours after insemination. It is cut in cross-sections, having a 7 M thickness, and 237 sections fall to the embryonic area. The flat incipient head fold has begun to develop, marking definitely the cranial margin of the neural plate. In this portion the ectoderm has been elevated above the surrounding embryonic shield. A broad and shallow neural groove, which gradually narrows cephalad, is present on the surface of the embryo. The primitive streak is well distinguished on the embryonic surface as of a transitional portion from the cranial neural groove into the caudal primitive groove. The notochord has acquired a tubular form at its caudal end in some more anteriorlj^ placed portions, but in the majority of the sections its ventral wall is opened into the yolk sac, to form the chordal plate. The caudal end of the notochord is fused to the cranial part of the primitive streak. No mesodermal somites are recognized nor can any indication of the coelomic cavity be detected.

Figure 2 was reproduced from the forty-first section, counting from the cephalic amnion attachment. The mesodermal layer is thicker than that found in the preceding specimen; this is due partly to the numerical increase of its component cells and partly due to a loosening of the arrangement of the cells. In the mesoderm no layers can be distinguished, the spindle-shaped cells having no definite arrangement. The loosening of the cell is more readily demonstrable on the ventral surface of the mesoderm; its ventral outline forms a zigzag contour, due to the shorter or longer protoplasmic processes which are seen extended from the ventral row of the mesodermal cells toward the underlying space. Moreover, as can be pointed out in the figure, some cells are projected into the underlying space beyond their surrounding group of cells, while others present a mitotic figure and have their axis directed to the space under the mesoderm and are pedunculated into the underlying space, but remain connected with the mesodermal layer by means of their narrow protoplasmic bridge. There can be seen a few spindleshaped cells, which appear completely detached from the mesoderm and he scattered between the mesoderm and entoderm. The area of the distribution of these cells, which we regard as angioblasts, more numerous in this embryo, extends over a wider range than is observed in the previous embryo. A glance at the figure will prove that the origin of these cells is derived from the mesoderm of the splanchnopleure.

In figure 3 there is presented a drawing of a sagittal section of an embryonic shield of approximately the same stage of development as that described under figure 2.

This series belongs to an embryonic shield of a guinea pig, removed from the uterus thirteen days and twelve hours after insemination. It includes 162 sections, having a 7 m thickness.

The figure was reproduced from a drawing of the fortieth section, counting from the lateral amnion attachment. This section passed through the flat head fold near its lateral margin. The fine of sectioning in this series was almost parallel to the mid axis of the embryonic shield. A study of the series shows that the developmental stage is just prior to the formation of the first mesodermal somite, which is indicated but not completely formed. The primitive streak extends approximately a third of the length of the embryonic shield. The general finding of the mesoderm is similar to that of the foregoing specimen. In the midsagittal plane the cranial end of the chordal plate terminates insensibly in the entoderm, where the pharyngeal membrane will be recognized. Cephalad to this membrane the pericephahc mesoderm is observed; its cranial hmit terminates freely at the cranial amnion attachment. This pericephahc mesoderm is continued into both mesodermal wings caudolaterally. The ventral surface of the mesoderm is loosened and presents a coarse appearance. Between the ventral surface of the mesoderm and the continuous layer of ectoderm angioblasts can be seen forming cell strands, ranging one after another, approximately parallel to the long axis. In the cross-section these cell strands may be shown as single cut cells. The faintly stained protoplasmic processes or sUghtly rotated, tenuous protoplasmic fibrils are given off from the surface of the cell strands. Some of these anastomose with each other and others are connected with the cells of the adjacent mesoderm. In this fashion their protoplasmic fibrils form a kind of feltwork between the mesoderm and entoderm. In brief, it is only a repetition of the processes which produce the angioblasts from the mesoderm of the splanchnopleure, as observed in the preceding embryo, but the angioblasts are a step further differentiated.

C. In figure 4 there is presented a cross-section drawing of an embryonic shield of a guinea pig, removed from the uterus thirteen days and eleven hours after insemination. This series includes 300 sections, having a 7 // thickness. In actuality this embryo presents only a slight advance in development over that discussed under figures 2 and 3.

The first mesodermic somite is indicated, but not completely formed. The intraembryonic coelomic space, which may be regarded as the future primitive pericardial cavity, considering its topographic position, shows simply a beginning of a very narrow cleavage in the lateral mesoderm of the cranial portion of the embryo. In some sections the two layers of the lateral plate of the mesoderm are separated from each other, and there can be seen narrow, discontinuous clefts between the mesodermic layers, while in other sections the whole mesoderm remains apparently solid. As a transition of these two extremes, in still other sections the coelomic space is shown as little more than a lineal cleavage. In brief, the coelomic cavity is forming from multiple foci and is not connected with the extraembryonic coelom. In the pericephalic mesoderm no coelomic space can be seen.

The figure reproduces a drawing from the sixty-third section, in which there can be seen an irregularly outlined splanchnopleure, from a relatively clear-cut contour of the somatopleure, separated by an incipient slip of the coelomic space. The splanchnopleure shows a slightly thicker layer of spindle-shaped cells; in some of them mitotic figures are present, indicating a proliferative activity. A number of angioblasts are scattered singly, while some others are grouped in a flat strand between the ventral surface of the mesoderm and entoderm.

Practically the same stage of development as that described in figure 4 can be seen in an embryonic shield, removed from the uterus fourteen days and four hours after insemination.

In figure five we see a drawing of the thirty-second section, counting from the lateral amnion attachment. This series, cut in the sagittal plane, includes 156 sections, having a 7 /x thickness. This section passes through the well upwardly projected head fold near its uphfted lateral margin. Under this head fold there can be recognized five discontinuous coelom spaces in the lateral plate of the mesoderm, each of which is interrupted by a substantial bridge. The mesodermal cell layer of the splanchnopleure is distinctly thickened and loosened. The spindle-shaped mesodermic cells assume a somewhat irregular arrangement. A number of them have disposed themselves in such a direction that their long axis is vertical to the ventral surface. A number of angioblasts are scattered under the mesoderm of the splanchnopleure and some of them are connected with this layer by their protoplasmic processes. Mitotic figures, seen in some of the mesodermal cells, show their proliferative activit3^ In some of the sections the discontinuous coelomic space can be seen in the pericephalic mesoderm, but it entirely disappears as it approaches the midsagittal plane, where the mesodermic layer has remained still in a solid condition, as can be found in figure 5B. In this respect this embryonic shield differs from that shown by Robinson and of several other workers. Robinson says that in mammals the mesodermic layer extends through the pericardial portion and is cleft into somatic and splanchnic layers before the head fold is formed. In our specimens the intraembryonic coelomic space is present discontinuously in the cranial region of the embryonic shield and totally absent as it approaches the middle plane of the pericephalic mesoderm, even though the head fold is already formed.


Stage II

The material on which the following description of stage II is based consists of several embryos, certain of which are cut transversely and others longitudinally.

A. This specimen was removed from the uterus of a guinea pig fourteen days and eleven hours after insemination. The series includes 307 cross-sections, having a 7 ^ thickness. A plastic reconstruction of the cranial portion was made with the Born method, and the whole shield, reconstructed for another purpose, was used for this study. This embryonic shield, as the model shows, presents a flat head fold, which is slightly more elevated than in the previous stage. The head fold can be divided into two primary parts. The cranial part is long and wide and projects over the cranial and lateral walls of the cranial body elevation. The caudal part is small and passes insensibly into the spinal portion. There is present a welldeveloped medullary groove in the cranial portion of the embryonic shield and its caudal end becomes gradually shallower until it disappears at the primitive streak in the caudal fourth of the embryonic shield. Its cranial end is terminated near the cranial extremity of the head fold. The deepest portion of the medullary groove corresponds to the region of the hindbrain plate. A well-marked anlage of the trigeminus is present as a thickening of the ectoderm. There are present three pairs

Fig. oA The 32nd section of a series of 156 sagittal sections of 7 m thickness of an embryonic shield of a guinea pig, removed 14 days 4 hours after insemination. The mesoderm is thickened and loosened, a number of discontinuous coelomic spaces is present, angioblasts are being produced from the splanchonpleura. X 150.

Fig. 5B The 77th section of the same series from which figure 5 was drawn, passing through practically parallel to the midsagittal line. The pericephalic mesoderm shows a relatively thinner layer than elsewhere and lies anterior to the primitive pharyngeal membrane, as the foregut has not yet developed. In accordance therewith, the reversal of the preumbilical region of the embrj'onic body does not occur. X 150.

Fig. 6 The 87th section of a series of 307 cross-sections of 7 ^ thickness of an embryonic shield of a guinea pig, removed 14 days 11 hours after insemination. The pericardial cavity opens widely, under the thickened splanchnopleura the endothelial tube is first formed in this embryo. X 150.


Fig. 7 The 27th section of the same series from which figure 6 was drawn embracing the nearly anterior margin of the head fold. The pericephalic mesoderm separates into two layers, by the lineal coelem space, which continues into the lateral pericardial cavity. X 150.


of mesodermic somites with a fourth pair forming. The foregut has begun to develop in the embryo; for the length of five sections its lumen is invaginated upward into the head fold.

Both the lateral primitive pericardial cavities are presented in the lateral plate of the mesoderm (fig. 6), which is completely separated into two lateral wings by the notochord, except in the cranial end of the embryonic shield, namely, beneath the cranial extremity of the head fold and in the region of the primitive streak. In these places two lateral wings come to fusion. In the mesoderm, which is produced by the fusion of both the lateral mesodermic wings in the middle line, beneath the cranial extremity of the head fold, in front of the pharyngeal membrane, a lineal cleavage can be recognized (fig. 7) by which the mesoderm is separated into two distinct layers. This coelemic space in the pericephalic mesoderm is formed by a forward extension of both the lateral primitive pericardial cavities into pericephalic mesoderm. These communicate with each other through this pericephalic coelomic space, which is now forming the craniomedian limb of the inverted U-shaped pleuropericardial cavity and may be accounted for as the essential future pericardial cavity. This cavity communicates freelj'^ with the future pleural cavity, which, in turn, passes into the peritoneal coelom. But this does not communicate with the extraembr}^onic coelom (fig. 8).

The reconstruction of the whole shield shows that the pleuropericardial cavity corresponds to a vague sweUing presented by the ectodermal laj^er on the dorsal surface of the model along the lateral margins of the neural plate, and their cranial extremities are connected with each other directly beneath the the cephalic end of the head fold. Therefore, the cranial extremities of the primitive pericardial cavity and of the head fold fall practically in the same level. The caudal extremities of both lateral pericardial cavities gradually disappear at the level of the caudal termination of the neural plate. And this corresponds to the gradual diminution of the prominent ectodermic swelling on the surface of the model. In this fashion, therefore, the rhomboidal shaped head fold is surrounded by the horseshoe-formed primitive pericardial cavity both laterally and cephalad.

In this stage the dimension of the craniomedian limb of the pericardial cavity is yet very narrow. Its ventrodorsal extent is not more than a Hneal cleavage (fig. 7), while its craniocaudal length extends throughout five sections. In tracing the lateral limbs from the craniomedian limb, however, the pericardial cavity gradualh^ increases in width until it reaches its maximum opposite to the hindbrain region (fig. 6), and then again a gradual reduction takes place behind this region until the coelomic cavity has completely disappeared in the region of the first mesodermic somite.

On the ventral surface of the model there can be seen the crescentic gut-groove of the entoderm at the cranial portion of the embryonic shield its apex being directed cranialward and deepened gradually until it reaches the opening of the fore-gut, which is invaginated cranialward between the ectodermal head fold and the craniomedian Umb of the pericardial cavity, as a horizontal diverticulum of the yolk sac. The base of the crescentic gut-groove is directed caudalward, and gradually becomes shallower, until it has entirely disappeared at the level of the hindbrain. On both sides of the gut-groove and along the foregut opening there is a rounded ridge running from the laterocaudal to the craniomedian end; in both position and direction, this ridge corresponds to the horseshoe-shaped pericardial cavity.

In this stage a number of angioblasts are scattered under the considerably thickened mesoderm of the splanchnopleure throughout the full extent of the pericardial cavity. A few angioblasts can be seen in the portion of the narrowly opened craniomedian limb of the pericardial space in which the mesoderm of the splanchopleure is in close contiguity with the underlying entoderm, and they increase in number toward the lateral limbs. In some sections in which the wide open pericardial cavity is present, endothelial tubes can be seen differentiated from the angioblasts lying under the mesoderm of the splanchnopleura, which is subsequently elevated from the entoderm and projected into the pericardial cavity as a prominent fold, as depicted in figure G. As the differentiation of the angioblasts into the endothelial tubes takes place irregularly, the distribution of both kinds of cells intermingles irregularly with reference to the level of sections; for example, even in the wide open pericardial region in some sections a tubular endothelium appears, while in the next succeeding section there are merely scattered angioblasts or cell strands of angioblasts. For this reason the invagination of the mesoderm of the splanchnopleura into the pericardial cavity as a prominent fold cannot be attributed simply to the development of the endothelial tubes, resulting in the increase of their volume. In this embryo, generally speaking, the angioblasts apparently predominate over the endothelium.

The dorsal aortae can be seen developed in the cephalad portion of the embryonic shield, while in many sections they are present as incompletely formed endothelial tubes resting on the entoderm on both sides of the notochordal plate (fig. 6), in their caudal extent they remain as cell strands of angioblasts.

In this embryo the foregut is present as a completely formed short entodermic tube, and the gut-groove, following caudally, is shown as a deep furrow. Not until a later stage is reached are the endothehal tubes completely developed. This corresponds apparently with the development of the human embrj^o, as described by Graf Spee. In the slightly younger embryonic shield the coelemic cavity in the pericephalic mesoderm is not yet formed in the median plane, where this is separated in many places by thin mesodermic bridges. But this condition is only temporary and both lateral pericardial cavities will communicate with each other, as is shown in this embryonic shield.

B. In figure 9 is represented a drawing of a midsagittal section of an embryonic shield of a guinea pig, removed from the uterus fourteen days and twenty-three hours after insemination. This series includes 172 sections, having a 7 m thickness. The figure represents a drawing of the eighty-fifth section, and this passes through the embryo just parallel and just lateral to the midaxis. As reckoned by age, this embryonic shield is just shghtly older than that discussed under figures 6, 7, and 8 but, judged by the stage of general development, the same findings can be noted. Here it is noticed that the craniomedian limb of the pericardial cavity is not more than a lineal cleavage in the pericephalic mesoderm, which extends in this plane from the more anteriorly situated extraembryonic mesoderm up to the pharyngeal membrane, where the mesoderm is entirely absent and the ectoderm and entoderm are in close contiguity.

In the peripheral two-thirds of the mesoderm in this section the cells have no definite arrangement, but are loosely and irregularly scattered. This portion can be seen as a continuation of the extraembryonic mesoderm, and the same condition is shown in figure 5B in the younger stage. In the central third of its extent the two layers of the cell band can be distinguished, namely, the mesoderm of the splanchnopleura and the somatopleura, and between them lies a craniomedian limb of the paricardial cavity. Its craniocaudal extent is short and its cranial extremity is approximately on the same level with that of the head fold. Its sagittal long axis forms an obtuse angle with the sagittal long axis of the embryonic shield.

¥\g. 9 The 8.5th section of a series of 172 sagittal sections, having a 7 m thickness. This embryonic shield was removed from the uterus of a guinea-pig 14 days and 23 hours after insemination. The pericephalic mesoderm separates into two laj^ers by the lineal coelem space, through which the two lateral pericardial cavities communicate with each other. The foregut has just begun to develop. X 150.

Fig. 10 The 83rd section of a series of 166 sagittal sections of a 7 m thickness of an embryonic shield of the guinea pig, removed 14 days 12 hours after insemination. The craniomedian limb of the pericardial cavity in the pericephalic mesoderm is wide open. The ventral wall of the pericardial cavity in figure 9 forms the caudal wall of it in this figure, as the reversing process occurs in the preumbilical region of the embryonic body, in conjunction with the development of the foregut, which in this embryo shows a longer lumen than in figure 9. X 150.

Fig. 11 The 4oth section of a series of 318 cross-sections, having a 7 /x thickness of an embryonic shield of a guinea pig, removed from the uterus 15 days 14 hours after insemination. This section passes through the forebrain plate near its anterior margin. The craniomedian limb of the pericardial cavity is wide open. The splanchnopleural fold projects into the pericardial cavity, rising from the underlying entoderm. This is especially prominent on the left side of the figure. Between the splanchnopleura and entoderm a number of angioblasts are scattered. X 150.


In the younger stage the pericephaHc mesoderm is situated anterior to the pharyngeal membrane, approximately in the same horizontal plane with the embryonic shield (fig. 5B). But in this stage it is brought ventrally to the pharyngeal membrane, as the foregut has begun to develop; the reversal of the preumbilical portion of the embryonic body accompanies this development.

C. In figure 10 is presented a drawing of a midsagittal section of an embryonic shield of a guinea pig, removed from the uterus fourteen days and twelve hours after insemination. This series includes 166 sections, having a 7 /x thickness. The figure is reproduced from a drawing of the eighty third section, passing through almost exactly parallel to the midaxis of the embryonic shield. As measured by age, this embryonic shield is slightly younger than that discussed under figure 9, but the general findings of the development are slightly in advance of that of the latter.

The craniomedian limb of the pericardial cavity, which lies under the foregut, extends dorsocaudally in a cranioventral direction, and has increased its dimensions in both the ventrodorsal and craniocaudal directions (fig. 10). Compared with the foregoing embryo (fig. 9), its sagittal long axis forms an angle a little more acute with the longitudinal axis of the embryonic body. Its caudal half presents the crescentic coelom cleavage, directing its convexity caudo ventral ward, while its cranial half still remains as a lineal slit. The cranial extremity of the craniomedian limb of the pericardial cavity is practically situated on the same level with that of the head fold (fig. 10). It may be demonstrated, when we compare figures 9 and 10, that the backward movement of the foregut opening from the cranial extremity of the head fold is greater than the rate of progress of the head fold forward from a certain fixed point. This actual backward progress of the foregut opening brings about the lengthening of the foregut. The foregut in this embryo is longer than in the preceding embryo. Its cranial extremity is slightly caudad to that of the craniomedian limb of the pericardial cavity. The ventral wall of the foregut coalesces with the ectoderm, indicating the pharyngeal membrane, while its dorsal wall corresponds to the cranial end of the notochord. The entoderm, which forms the dorsocaudal wall of the craniomedian limb of the pericardial cavity, is reflected from the foregut opening to the ventral wall of the craniomedian limb of the pericardial cavity, representing the so-called cardiac fold (repli cardiaque Tourneux). The cranial wall of the craniomedian limb of the pericardial cavity is formed by the ectoderm, which is reflected from the pharyngeal membrane to the proamnionic region.

A few cell strands of angioblasts can be seen between the mesoderm of the splanchnopleura and the underlying ectoderm. The splanchnopleura is present, its convexity turned caudoventrally, in accordance with the entodermic cardiac fold. Its central part has begun to invaginate into the pericardial cavity, rising from the underlying entoderm. Between these two layers the angioblasts are scattered.

Stage III

The material on which the description of stage III is based consists of two embryos, one of which was cut transversely and the other longitudinally.

A. This specimen was removed from the uterus of a guineapig fifteen days and fourteen hours after insemination. This series includes 318 sections, having a 7 /^ thickness. The plastic reconstruction of the cephalic portion of the embryo was made with wax plates, and the whole shield, reconstructed for another purpose, was used for this study.

The neural groove extends from the cranial end to the caudal amnion attachment. It is wide and shallow in the caudal portion, while it is narrow and deepens toward the head fold. The head fold is divided into two primary vesicles; the cranial vesicle is wide and long, projecting laterally and cranially over the cranial and lateral walls of the cranial body elevation. The caudal vesicle is small and passes insensibly into the spinal portion. The anlagen of the trigeminal ganglia, as well as the rudiment of the otic ganglia, are to be seen. Four somites are completely segmented, besides in their cranial and caudal territory, a somite is in process of formation. The dorsal aortae and the first aortic arch are present, while the ventral aortae are not yet completely differentiated. In the region of their anlagen the angioblasts are irregularly distributed. The foregut extends throughout twenty-two sections, appearing first in the twenty-seventh section and continuing to the forty-ninth section, while the craniomedian limb of the pericardial cavity extends throughout sixteen sections, appearing in the twenty-third section and continuing to the thirty-ninth section. The cranial end of the head fold appears in the eighth section, on account of the forward progress of the head fold. This fact can be demonstrated in the dorsal surface of the whole reconstruction model, in which the prominent swelUng of the dorsal surface of the pericardial cavity is much more distinct than that of the foregoing model. The cranial extremity of the pericardial cavity disappears under the head fold slightly caudad to its cranial margin.

In this embryo the mesoderm of the splanchnopleural projects into the pericardial cavity, forming prominent folds, already presented in the previous stage, but in this stage is well developed. These folds are converted on both sides into continuous myocardial tubes. Their dorsal surfaces approach the dorsal wall of the pericardial cavity, coming nearly into contact with it. These lateral myocardial tubes are best developed at the level of the hindbrain, where they are relativel}' dilated and contain the well-developed endothelial tubes. On tracing cranial ward, both myocardial tubes gradually diminish in height and width, until they finally disappear opposite to the foregut opening on its left side, while on the right side the myocardial tube continues into the caudad portion of the craniomedian limb of the pericardial cavity, converting it into the prominent rounded ridge of the mesoderm of the splanchnopleura. In this region the thickened mesoderm of the splanchnopleura, present as a somewhat flattened fold, is elevated above the underlying entoderm. In the space between these two layers a number of angioblasts can be seen (fig. 11 and 12). In tracing still farther cranialward, the relatively thin layer of mesoderm of the splanchnopleura remains attached to the underlying entoderm; between them no angioblasts can be seen (fig. 13).


Fig. 12 Dorsal view of the reconstruction of the same embryonic shield (stage III, A) from which figure 11 was drawn. Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. At the caudal part of the craniomedian limb of the perciardial cavity the splanchnopleura projects into the pericardial cavity, forming the prominent fold, which is absent in front of the cranial extremity of the myocardial tube on the left side. E-D indicates plane of section of figure 11. X 100.

Fig. 13 Dorsal view of the reconstruction of the same embryonic shield (stage III, A) from which figures 11 and 12 were drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to show the underlying endothelial tubes and angioblasts. Angioblasts are scattered under the splanchnopleural fold at the cuadal part of the craniomedian limb of the pericardial cavity, almost connecting both cranial extremities of the lateral endothelial tubes. But angioblasts are absent in front of the cranial extremity of the lateral endothelial tube on the left side, where the splanchnopleura has not risen from the underlying entoderm. X 100.


It can be ascertained that the formation of the mesodermal splanchnopleural folds occurs in loco and progresses cranialward, until both cranial extremities of the myocardial tubes will ultimately unite and communicate with each other at the craniomedian limb of the pericardial cavity. The craniomedian limb of the pericardial cavity increases its dimensions both in the ventrodorsal and in the craniocaudal directions, while the formation of the myocardial anlage in this portion remains in its primitive condition. In the hindbrain region the pericardial cavity reaches its maximum width in proportion to the myocardial and endothelial development. But it shows here a rather narrower space in the ventrodorsal direction, on account of the dorsal expansion of the myocardial tubes. In tracing still further caudalward, the pericardial cavity gradually narrows until it entirely disappears in the somitic region, parallel with the gradually diminishing splanchnopleural folds and endothelial tubes.

The endothelial tubes are differentiated at great length, extending throughout nearly the whole extent of the lateral pericardial cavity. But in many places these tubes are irregularly interrupted, their continuity bridged by angioblast cords. The endothelial tubes terminate cranially opposite to the foregut opening on the right side and slightly caudad to it on the left side. In front of these terminations a number of angioblasts are scattered. Extending still farther ci'aniomedially, by means of these angioblasts, the cranial extremities of the endothelial tubes are connected with each other through the middle plane underneath the flat splanchnopleural folds of the craniomedian limb of the pericardial cavity (fig. 13). There is a distinct significance in the fact that these angioblasts are directly derived from the mesoderm of the splanchnopleural cells in loco. Moreover, in some other parts the angioblasts or endothelial cells are undoubtedly connected with the thickened and indented mesoderm of the splanchnopleura. Therefore, it is conceivable that the productive activity of these cells from the mesoderm of the splanchnopleura is still continued in this embryo.


Stage IV

The material on which the following description of stage IV is based consists of two embryos, one of which was cut transversely and the other longitudinally.

A. This specimen was removed from the uterus of a guineapig fourteen days and eight hours after insemination. This series includes 566 sections, having a o ^ thickness, from the cranial margin of the head fold to the caudal end of the mesodermic thickening of the allantois. The plastic reconstruction of the cephahc portion of the embryonic body was made with wax plates.

The head fold has progressed cranial- and dorsalward. Its cephahc extremity is represented in that of the embryonic shield. There are present seven pairs of mesodermic somites, the first and last being small and indistinctly segmented. The neural groove extends from the cranial end to the caudal amnion attachment. In the hindbrain region the neural groove shows very narrow and deep as both the neural plates approach each other.

In the model it can be recognized that the craniomedian limb of the pericardial cavity increases its dimensions in the ventrodorsal direction, while its lateral and craniocaudal extent remains approximately unchanged in comparison with the previous stage III. The cranial extremity of this portion extends at its dorsal part into the mesodermic cavity of the mandibular region on both sides. While their outhne gradually approaches the horizontal plane, the caudal extremity of this portion is continued into both the lateral pericardial cavities, which gradually diminish in width caudalward. In the region of the second somite they entirely disappear.

The formation of both the lateral myocardial tubes, which has been discussed in stage III, are considerably developed and have so far progressed cranialward, that their cranial portions have partially come into contact and been fused together. Through this portion the myocardial tubes communicate with each other. On the dorsal surface of this fused portion of the lateral myocardial tubes the myocardial \Yalls are reflected directly onto the dorsal wall of the pericardimn, thus forming the dorsal mesocardium on both sides. Between the lateral mesocardial layers there is present an irregular triangular space, which we purpose to designate as the intermesocardial space and through which the endothelial offshoots come out from the myocardial cavity onto the space between the mesocardial layers and the floor of the foregut. Its apex is directed craniaiward, where the lateral mesocardial layers come in contact, marking the cranial margin of the communicating myocardial cavity. Its basal portion is directed caudalward and corresponds to the foregut opening, by which the lateral mesocardium layers diverge from each other and continue farther caudalward along the lateral myocardial tubes (fig. 14). Between the abovementioned adherent cranial margin of the mesocardium and the foregut opening, the lateral myocardial cavities communicate with each other across the middle plane to the extent of eight sections. From this communicating myocardial cavity are sent out two short cranial diverticula on either side, separated by a septal wall in the middle plane, corresponding to the cranial extremities of the lateral myocradial tubes. These diverticula are present as the rounded myocardial horns, directed cranialward and separated from each other by their own inner walls. These inner walls are caudally converted into a wedge-shaped prominent ridge, which continues into the communicating portion of the myocardial cavit}^ and gradually diminishes caudalward (fig. 15). The communicating portions of the lateral mj'^ocardial tubes are directly continued into the lateral myocardial tubes caudolaterally on both sides and they are separated from each other by the foregut opening. The ventral wall of the communicating portion of the myocardial cavity is reflected onto the ventral wall of the pericardium and is recognized only in the caudal portion. The reflection points from the myocardium to the ventral pericardial wall are fused together at the cranial part, but at the caudal part the reflection points diverge from each other and a triangular space remains between them in just the same manner as can be seen in the dorsal wall.


This ventral triangular space is covered by the entoderm cephalad to the foregut opening, while the dorsal intermesocardial space is covered by the foregut floor. Ventrall}" to the communicating mj'ocardial cavity, the pericardial cavity passes from side to side, because of the absence of the ventral mesocardium. Along the ventral mesodermic reflection the anlage of the septum transversum of His will be presented in the future development, and the mesodermic reflection may be erroneously taken for the ventral mesocardium, if a single section of this portion should be examined, as many workers claim the existence of the ventral mesocardium in mammals.



Fig. 14 Dorsal view of the reconstruction of an embryonic shield (stage IV). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The two lateral myocardial tubes are partially confluent, slightly cephalad to the foregut opening. The two short cranial horns of the myocardial tubes are directed toward the top of the page. X 100.

Fig. 15 Dorsal view of the reconstruction of the same embryonic shield (stage IV) from which figure 14 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the underlying endothelial tubes. The two lateral endothelial tubes approach most closely to each other at the confluent myocardial portion, where independent endothelial cells are interposed between the two tubes. X 100.


The endothelial tubes are well developed and are enclosed within the myocardial cavities on both sides. Their lumina are patent throughout their cranial extent, their cranial extremities terminate blindly opposite to the cranial extremities of the myocardial tubes, where the myocardial tubes are projected into the pericardial cavity, like the rounded lateral horns on either side, which contain the cranial extremities of the myocardial cavity. In tracing caudally, the endothelial tubes reduce their caUbers gradually and they are irregularly interrupted in their continuity by angioblasts. They entirely disappear in the somitic portion, where the lateral pericardial cavities assume a narrow and horizontal space and the splanchnopleural folds have entirely disappeared. The lateral endothelial tubes are most remarkably dilated and considerably approximated to each other at the communicating myocardial cavity, where the independent intermediate endothelial cells can be seen between the endothelial tubes. Throughout many sections in the communicating myocardial cavity, the endothelial tubes give off their endothelial offshoots from their dorsomedian aspects, coursing dorsolateralward, between the dorsal mesocardium and the floor of the foregut. These offshoots may be considered the future truncus arteriosus.

Owing to the gradual transition from these dilated endothelial tubes into the portion of the vitelline veins caudalward, their demarcation cannot be pointed out on the endothelial tubes nor on the myocardial tubes.

The dorsal aortae and the first aortic arch are completely developed, while the ventral aortae are incompletely differentiated. In their anlagen a number of angioblasts are distributed irregularly.

Stage V

The material on which the following description of stage V is based consists of two embryonic shields, which were cut transversely The partial plastic reconstruction of the cephalic portion and the reconstruction of the whole embryonic shield, made for another purpose, were used for this study.

A. This specimen was removed from the uterus of a guinea pig fourteen days and eight hours after insemination. The series includes 612 sections, having a 5 m thickness. As measured by age, this embryonic shield is shghtly younger than that discussed in stage IV. As judged by the stage of general development, it is slightly more advanced, indicated by the facts that eight somites are present and that the medullary groove is much deeper and narrower in the hindbrain region, so that to a great extent both neural plates are in contact; here it passes insensibly into the spinal region. The forebrain plate still remains wide open, projecting cranially and laterally over the cranial and lateral wall of the anterior body elevation. It is, moreover, bent considerably ventralward. In the model it can easily be recognized that, owing to the fact that this embryonic shield is considerably folded off from the yolk sac, it is in general thicker in the ventrodorsal diameter and narrower in the lateral diameter than that in stage IV. In accordance therewith, the cranial extremities of the lateral myocardial tubes are forming a more acute angle than that of the previous stage. The craniomedian hmb of the pericardial cavity increases its ventrodorsal and craniocaudal dimensions, while its lateral diameter diminishes on comparison with the embryo of stage IV, in proportion to the rounded outUne of this embryo. The craniomedian Umb of the pericardial cavity is elongated at its dorsal part into the mandibular mesoderm. In coursing caudalward, the lateral pericardial cavities graduallj^ diminish their width, and at the same time their outline approaches the horizontal plane as a whole. They disappear entirely opposite to the fourth somite. The direction of the lateral myocardial tubes tends to their nmning parallel to each other. The lateral myocardial tubes are considerably dilated at their cranial portion, where they abruptly become voluminous in comparison with their caudal portion. The transitional points of these two different portions are situated a little caudad to the foregut opening on both sides, where the myocardial tubes mark shght indentations. These indentations indicate the future atrioventricular constriction (fig. 16).

The cranial extremities of the lateral myocardial tubes become more voluminous as compared with those of the previous stage and are projected cephalad into the pericardial cavity as large lateral rounded horns. They are separated from each other by their own inner walls, which fuse caudally into one septal wall and, as we trace still farther caudally, we find them converted into the prominent wedge-shaped ridge which projects into the communicating myocardial cavity. This ridge gradually diminishes in height caudalward until it has entirely disappeared in the middle of the communicating cavity (fig. 17).

The dorsal wall of the fused myocardial tubes is reflected directly onto the dorsal wall of the pericardium, forming the dorsal mesocardium on both sides. These lateral mesocardial layers come to fusion in a region a little cephalad to the foregut opening, where it makes the cranial margin of the communicating myocardial cavity. On the dorsal surface of the fused myocardial portion an irregular intermesocardial space can be seen, covered by the floor of the foregut. Its apex is directed cephalad, corresponding to the point where the lateral mesocardium layers are fused together. Its base is directed caudad, corresponding to the foregut' opening. Its sides are formed by the lateral mesocardial layers. Corresponding to this intermesocardial space, the lateral myocardial tubes communicate with each other through the median plane throughout the extent of nine sections. In a similar way, the ventral wall of the fused myocardial tube is reflected onto the ventral wall of the pericardium, but only in its caudal portion. Between these two lines of the mesodermal reflection there remains a narrow space free from the mesoderm and covered directly by the entoderm. However, these lines of reflection on the ventral wall are disposed in a rather transverse direction and are located only for a short extent in the caudal part of the communicating myocardial tube, while on the dorsal surface the lines of reflection of the mesocardium are directed rather longitudinally and extend throughout the whole length of the eoniinunicating myocardinal tube. The communicating portion of the myocardial cavity terminates blindly in the cranial diverticulum cephalad, corresponding to the cranial extremities of the lateral myocardial tubes, while caudally it is elongated into the lateral myocardial tubes, which are diverged by the foregut opening, and their lumina are gradually diminished toward the somitic region.


Fig. 16 Dorsal view of the reconstruction of an embryonic shield (stage V). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The two lateral myocardial tubes become quite voluminous, especially at their cranial portions, which continue farther caudalward, gradually diminishing in size. The atrioventricular constriction is marked on the surface of the myocardial tubes, caudad to the foregut opening on both sides. The two cranial horns of the myocardial tubes become enlarged, and they are directed toward the top of the page. X 100.

Fig. 17 Dorsal view of the reconstruction of the same embryonic shield (stage V) from which figure 16 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the underlying endothelial tubes, which are apparently enlarged at their cranial portions, where they most nearly approach each other. X 100.


In general, the endothelial tubes are much more developed than those of the previous stage, since they have become deeper and wider. At the widest portion of the endothelial tubes, corresponding to the communicating myocardial cavity, the endothehal tubes approach each other so that they come nearly into contact. On these portions, throughout many sections, the endothelial tubes give off a number of endothehal offshoots from their dorsomedian surface into the space between the dorsal mesocardium and the foregut floor. From these portions they become gradually narrower, toward both the cranial and caudal directions. The cranial extremities of the endothelial tubes terminate blindly opposite to the cranial myocardial extremities, while caudally they continue into the portion of the vitelline veins. The endothelial tubes assume the distinctly narrow calibers opposite to the atrioventricular constriction. The endothehal tubes sprout out into innumerable tenuous fibrils, often forming a feltwork, which occupies the ^^■ide space between the myocardium and the endothehum.

The dorsal aortae and the first aortic arch are developed, while the ventral aortae are not completely formed, as in their anlagen a number of angioblasts are scattered.

Stage VI

The material on which the following description of stage VI is based consists of one embryo, cut transversely. The plastic reconstruction of the cephalic portion of the embryo was made with wax plates.

This specimen was removed from the uterus of a guinea pig fourteen days and eight hours after insemination. The series includes 582 sections, having a 5 micron thickness. As measured by age, this embryonic shield is the same as that of the previous embryo. As reckoned by general development and special development of the heart, it is considerably advanced over the preceding embryo. Eight well-segmented somites are present. The medullary groove, extending from the cranial end to the caudal amnion attachment, is as deep and narrow as in the previous embryo. The form of the embryonic shield is, in general, more rounded in comparison than with the foregoing embryo, as the ventrodorsal diameter of this embryo is apparently increased while its lateral diameter has remained unchanged. The first visceral pouch and the oral pit are developed ; in these places the entoderm coalesces intimately with the ectoderm.

The reconstruction shows that at this stage of development the craniomedian limb of the pericardial cavity increases considerably in the craniocaudal dimension and in the ventrodorsal dimension. The craniomedian limb of the pericardial cavity communicates caudally with the lateral pericardial cavities. On coursing caudally, these become gradually narrower, until they disappear entirely opposite to the sixth somite. The craniomedian limb of the pericardial cavity is elongated cranially at its dorsal part into the mandibular portion, lying under the foregut floor. The caudal half of the ventral surface of the craniomedian limb of the pericardial cavity is covered by the yolk sac, while its cranial half and all other surfaces are covered by the amnion.

In this stage the fused portion of the lateral myocardial tubes increases remarkably throughout its craniocaudal extent. In accordance therewith, the cranial bilateral myocardial horns, which correspond to the cranial extremities of the lateral myocardial tubes, and predominate in the craniomedian limb of the pericardial cavity in the previous stage, apparently diminish their dimensions in this embryo, and show only their rudiments. They assume only short and wide bilateral processes, divided by a shallow and wide intervening groove. In the previous stage this groove was present as a narrow and deep sulcus. Subsequently, the inner walls of these horns diverged markedly from each other (fig. 18). The wedge-shaped ridge which, in the previous stage, projected into the communicating myocardial cavity at its middle cranial wall, as a caudal continuation of the converted septum walls of the cranial bilateral myocardial horns, is considerably retired cranialward in this embryo. Therefore, the cranial wall of the communicating myocardial cavity approaches in such a manner toward the cranial wall of the pericardium as to come nearly into contact with it and, simultaneously, the communicating myocardial cavity is elongated cranialward. The fused portion of the myocardial tube becomes distinctly narrower and thicker in comparison with that of the previous stage. In two of the same magnified models ( X300) the widest lateral diameter of this portion is calculated as 14.5 cm. in this embryo, instead of 19 cm. of the previous embryo, while the ventrodorsal diameter of this portion presents 5.1 cm. in this embryo and 3 cm. in the former embryo. The fused myocardial tube is reflected directly onto the dorsal wall of the pericardium, ?,nd thus forms the dorsal mesocardium on both sides. Between the lateral mesocardial layers there can be seen alongrectangularintermesocardial space; its plane is approximately parallel with the horizontal. Its cranial margin is formed by the fused portion of the mesocardial layers in the middle line; its caudal margin corresponds to the foregut opening, while both lateral margins are represented by the lateral mesocardial layers, which continue farther caudalward, diverted by the foregut opening. In accordance with this mesocardial space, both myocardial tubes communicate freely with each other through the median plane, and thus form



Fig. 18 Dorsal view of the reconstruction of an embryonic shield (stage VI). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardial tubes. The confluent portion of the two lateral myocardial tubes is considerably elongated in the craniocaudal direction. The two cranial horns of the myocardial tubes diminish to short rudiments, as their septal wall retires cranialward. They are directed toward the top of the page. X 100.


Fig. 19 Dorsal view of the reconstruction of the same embryonic shield (stage VI) from which figure 18 was drawn. Dorsal wall of the pericardium and of the myocardial tubes have been removed to expose the endothelial tubes. The two lateral endothelial tubes have fused and communicate with each other at a middle third of the ventricle, where they most closely approach each other in figure 17. The lateral endothelial tubes apparently diminish their size opposite to the atrioventricular constriction. X 100.

the craniomedian limb of the myocardial cavity. This limb of the myocardial cavity is bifurcated caudally into the lateral myocardial tubes, which are diverged from each other by the foregut opening and in which the viteUine veins are enclosed, leading cranially into the craniomedian limb of the myocardial cavity (fig. 19). In brief, the myocardial anlage presents cranially two short rudimentary horns, which terminate blindly as the cranial myocardial extremities, while caudally there are two lateral myocardial prolongations, into which the vitelUne veins enter. Between these four extremities the myocardial wall is relatively considerably expanded dorsal, lateral, ventralward and contains the widest portions of the endothehal tubes, which are united in the communicating cavity. This region corresponds to the future ventricle region. On the midsagittal hne of the ventral surface of this fused myocardial portion a shallow longitudinal groove can be seen.

On the ventral aspect of the fused myocardial portion the ventral myocardial layer is reflected onto the ventral wall of the pericardium, but this is limited to a short length, extending only to the caudal part of this portion.

The transition from the cranial expanding ventricle to the caudal myocardial prolongations is indicated by an annular constriction, which is produced by the infolding of the whole myocardial wall, a little deeper on the right side than on the left. This indicates the atrioventricular constriction and is situated at the level slightly cephalad to the foregut opening on both sides.

Proceeding caudally from this constriction, the lateral myocardial tubes reduce their calibers abruptly and diverge from each other. On the surface of these caudal prolongations of the myocardial tubes there are present indefinite, shallow indentations at the level shghtly caudad to the foregut opening, and these constrictions have been regarded as the future sinoatrial construction.

The lateral endothelial tubes are partially fused and their lumina communicate with each other, for their inner walls have been absorbed throughout seven sections. This portion is situated in the middle third of the bulging ventricle anlage, where in the previous stage both endothelial tubes were closely approximated and presented the greatest dilation and where in. this embryo also the endothehal tube is greatly expanded.

From this fused portion of the endothelial tube the two cranial horns and two caudal prolongations are given off. The bilateral cranial horns are short and gradually diminish in size cranialward, until they terminate in a pointed apex, opposite to the cranial extremities of the myocardial horns. From the dorsomedian part of these cranial endothelial horns a number of endothelial branches are given off. These endothehal branches are connected with the ventral aortae through the intermesocardial space.

Bilateral caudal prolongations are given off on both sides from the caudal aspect of the fused endothelial tube. Continuing caudalward, both endothelial tubes gradually diminish their cahbers, until the lumina have entirely disappeared at the atrioventricular constriction. Still further caudalward from this constriction, again they begin to dilate their calibers gradually and continue into the endothelial vitelline veins without any indication at their transitional point. At the atrioventricular constriction the endothelial tubes closely approach the infolding of the myocardial wall, while in the ventricle the intervening space between the myocardium and endothelium is relatively wide.

From the caudal aspect of the fused endothelial tube another intermediate endothelial branch is given off caudall3^ This branch is situated between the endothehal prolongations and terminates at the atrioventricular constriction.

The dorsal aortae and the first aortic arch are developed, while, in many sections, the ventral aortae are interrupted by angioblasts.

Stage VII

The material on which the following description of stage VII is based consists of one embiyonic shield, which is cut transversely. The plastic reconstruction of the cephalic portion of the embryo was made from wax plates.

The specimen was removed from the uterus of a guinea-pig fourteen days and eleven hours after insemination. The series includes 418 sections, having a 7 ^ thickness, from the cephalic end of the head fold to the end of the mesodermic thickening of the allantois. Xine pairs of well-segmented somites were found, each somite showing a thick wall and enclosing a uniform cavity with a compact arrangement of cells, except two caudal somites, which contained no cavity nor presented the regular arrangement of the cells.

The medullary canal is closed from the second somite to the last, but elsewhere the medullar}^ plates remain open. The notochordal plate is separated from the entoderm throughout from the second somite to the last, but elsewhere it is still connected with the entoderm. The first and second visceral pouches are developed, in which the ectoderm and entoderm have tightlycoalesced. The oral pit is formed and the pharyngeal membrane becomes quite thin.

In this embryo the pericardial cavity is closed in all directions, forming a sac, except at the dorsal part of its caudal extremities, where the pleuropericardial passages are opened on each side. These passages are represented by the narrow coelomic space, which continues farther caudalward into the peritoneal cavity and they are situated dorsomedian to the myocardial coat of the vitelline veins. From the dorsal part of the cranial extremity of the pericardial cavity a slit-like space is elongated into the mandibular region.

The surface of the pericardium is covered by the yolk sac ventrally, while laterally, cranially, and dorsally it is covered by the amnion. The pericardial cavity shows a wide space around the myocardium. Between the cranial extremity of the myocardium and the cranial wall of the pericardium there remains a wider interval than that of the embryo of stage VI.

The myocardium presents cranially an undivided cranial extremity, which expands considerably in all directions and assumes a sac form, while caudally this myocardial sac is bifurcated into two rather slender myocardial prolongations, in which the endothelial vitelHne veins are enclosed on both sides. The transition from the cranial myocardial sac to the bilateral myocardial tubes is indicated by the deep atrioventricular construction, at the level slightly cephalad to the foregut opening. This constriction is produced by the infolding of the whole myocardial wall and shows apparently deeper on the right sidfe than on the left. On the ventral surface of the ventricle there can be seen a shallow groove in the midsagittal line at its caudal half, and in accordance therewith the whole thickness of the myocardial wall is slightly infolded into the myocardial cavity.

This superficial groove and the infolding of the myocardial wall are located in the caudal half of the ventricle, for they gradually disappear toward its cranial extremity, which is of conical form. The ventral myocardial layer is reflected onto the ventral wall of the pericardium, but is confined to the atrial region to a short length opposite to the foregut opening.


Fig. 20 Dorsal view of the reconstruction of an embryonic shield (stage VII). Dorsal wall of the pericardium has been removed to show the pericardial cavity and the myocardial tubes. The myocardium shows cranially a single sac-formed ventricle, which bifurcates into two slender myocardial tubes caudalward. The transition between them is marked by the atrioventricular constriction cephalad to the foregut opening. A single cranial extremity of the ventricle is directed toward the top of the page. X 100.

On the dorsal aspect the myocardial wall is reflected onto the dorsal wall of the pericardium and forms the dorsal mesocardium on both sides. The cranial extremity of the dorsal mesocardial attachment corresponds to a middle third of the ventricle, and from this point it continues farther caudalward. Consequently, the cranial half of the ventricle is free from the mesocardium (fig. 20). Between the lateral mesocardial layers there can be seen an irregular triangular intermesocardial space. Its plane is directed caudodorsalward on account of the abrupt dorsal expansion of the ventricle. Its apex is, therefore, situated caudoventrally and is formed by the lateral mesocardial layers, approaching contact, opposite to the atrioventricular constriction, while its basal portion is directed craniodorsally and corresponds to the portion where the lateral mesocardial layers come to fusion and mark their cranial extremities.

On the caudal surface of the ventricle the right half assumes an apparently wider dimension than the left. This is attributed partly to the exceeding expansion of the myocardial wall in the laterocaudal direction on the right half and partly to the deeper infolding of the atrioventricular constriction on the right side. On this bulging portion of the caudal extremity of the ventricle at the right half the caudal extremity of the right ventricle will be developed, and this is shown distinctly in the next stage.

The lateral myocardial tubes of the atrium are diverged from each other by the foregut opening. The right atrium is practically beginning just opposite to the foregut opening, while the left one begins slightly cephalad to it, for in comparison with the right side, the left atrioventricular constriction is shallower and situated slightly cephalad.

On .the myocardial tubes of the atrial portion indefinite indentations, indicated as the sino-atrial constriction, can be recognized. These are between the atrioventricular constriction and the level of the pleuropericardial passages. This is especially noticeable on the left side.

The lateral endothelial tubes are fused together throughout the cranial two-thirds of the ventricle. Its cranial extremity terminates as a single conical apex opposite to the cranial extremity of the myocardial ventricle. At this fused portion the endothelial cavities communicate with each other and show considerable dilation. In tracing caudalward from this united portion, the tubes are separated from each other, even though they appear to approach each other. At the atrioventricular constriction the endothelial tubes present their smallest size and simultaneously they approach closely to each other. Proceeding still farther caudally from this portion, they are diverged from each other by the foregut opening and again assume a gradual enlargement of their calibers. At the caudal part of the ventricle, where the endothelial tubes are separated, they present an asymmetrical size, for the right one is extraordinarily de


Fig. 21 Dorsal view of the reconstruction of the same embryonic shield (stage VII) from which figure 20 was drawn. Dorsal walls of the pericardium and of the myocardium have been removed to expose the endothelial tubes. The two lateral endothelial tubes have fused and communicate with each other throughout the cranial two-thirds of the ventricle. The ventricular endothelial tubes show a distinct asymmetrj^, due to the extraordinary enlargement of the right side, regardless of the fused or non-fused portion. The endothelial tube is elongated dorsalward from the dorsal surface of the enlarged right endothelial tube, passing through the intermesocardial space. This endothelial elongation is bifurcated into the two lateral branches, which are continuous into the ventral aortae. X 100.

veloped and expended in the lateral and caudal directions, forming a curvature whose convexity is turned laterocaudalward. At this endothelial portion the endothelial tube is elongated vertically dorsalward and comes out from the myocardial cavity onto the foregut floor through the intermesocardial space. The cranial part of this endothelial elongation is bifurcated into two later branches which connect it cranially with the corresponding ventral aortae. The asymmetrical development of the endotheUal ventricle corresponds to the myocardial asymmetry in the ventricle, which has been mentioned above. In this part of the ventrical the most important change will be noted in the next stage, here developing, namely, the right limb of the ventricle. And this change is initiated in this embryo as a considerable asymmetrical expansion of the caudal extremity of the ventricle on the right side.

At the ventricle the endothelial tubes are separated from the myocardial wall by a wide intervening space, but they gradually approach each other in the direction of the atrioventricular constriction caudalward, as in the caudal part of the atrium no more intervening space can be pointed out between the myocardial wall and the endothelium (fig. 21).

The transition from the atrial endothelial tubes into the sinus portions can be pointed out by the abrupt decrease of the endothelial caliber on the left side, corresponding to the relatively distinct sino-atrial constriction of the myocardium. But on the right side the atrial endothelial tube continues farther caudalward without any demarcation, in accordance with the relatively indistinct myocardial constriction.

On both sides the ductus cuvieri can be seen opening into the sinus venosus. The dorsal aortae and first aortic arch are well developed, while in many places the ventral aortae still retain the plexus form.

Stage VIII

The material on which the following description of stage VIII is based consists of one embryonic shield, which is cut transversely. The plastic reconstruction of the cephalic portion of the embryo was made; the reconstruction of the whole embryonic shield, made for another purpose, was used for this study.

This embryo was removed from the uterus of a guinea pig fourteen days and twelve hours after insemination. The series includes 408 sections, having a 10 m thickness, from the cephahc end of the head fold to near the caudal extremity of the allantoic mesodermic thickening. Nine pairs of the well-segmented somites are present and the tenth is in process of formation; each somite shows the thick wall and encloses a uniform cavity. The neural canal is closed from the region of the hindbrain to the region of the last somite, though in the foreand midbrain region it still remains open. The cranial flexure is shown in the region of the midbrain and that of the forebrain is bent downward and forward, bringing it to a plane parallel with the long axis of the hindbrain. The foregut is closed to the first somitic region. The first visceral pouch is found in the region of the midbrain with the entoderm and ectoderm coalesced, while the second visceral pouch is in process of formation also in the region of the hindbrain, in which region between the entoderm and ectoderm a thinner layer of the mesoderm than elsewhere is found interposes. The oral pit is well formed, the pharyngeal membrane is present as a thin single layer of cells. On the ventral surface of the model the edge of the foregut opening is elevated by two prominent Umbs, which on each side are confluent into an extensive ventral bulging cranially to the foregut opening. In position and direction this corresponds to the pericardial cavity, containing the voluminous heart.

The pericardial sac is closed except at the dorsomedian part of its caudal extremity, where the pleuropericardial passages are found. In the region of the sinus venosus each one of the bilateral pericardial cavities is divided into a median and a lateral part by the myocardial fold and in the region of the pleuropericardial passages the lateral parts of the bilateral pericardial cavities terminate blindly caudalward, so that only their median portions are continued caudally into the peritoneal cavity. Accordingly, these passages are represented merely by narrow, crescentic coelomic spaces, dorsomedian to the viteUine veins, proceeding caudally and mesially, crossing with the vitelline veins, which run cranially and mesially.

On account of the considerable enlargement of the muscular heart, the pericardial space is, in general, proportionately reduced, especially in the well-developed ventricular portion a simple narrow space surrounds the muscular sac of the ventricle.

In the region of the atria and the sinus venosus a relatively wide space intervenes between the rather flat muscular tubes and the pericardial wall (fig. 22). There are present two distinct constrictions on the tubular muscular heart, infolding the whole thickness of the myocardial wall, one of which represents the atrioventricular constriction and the other the sino-atrial constriction.

The atrioventricular constriction is present asymmetrically on both sides; on the right side it is marked more deeply and situated sUghtly caudad, while on the left side it is shallower and lies a little cephalad. Therefore, this constriction forms an obhque angle with the long axis of the muscular heart.

On the contrary, the sino-atrial constriction is marked more deeply on the left side and is situated slightly cephalad to the foregut opening, while on the right side it is less deeply constricted and is situated slightly caudad, just opposite to the foregut opening.

The ventricle can be divided into two lateral limbs by a ventral and a dorsal longitudinal sulcus. On the dorsal surface it is marked along the attachment line of the dorsal mesocardium and terminates caudally opposite to the right margin of the atrioventricular constriction, while its cranial extremity gradually disappears at the portion where the bulbus cordis is differentiated from the dorsal wall of the ventricle. On the ventral surface the longitudinal sulcus extends to a caudal third of the ventricle.

At the caudal part of the ventricle, for a short length, both lateral limbs are divided into two completely independent cavities by the septal wall. The caudal extremity of the right ventricle is shown as the conical process, projecting caudolaterally and terminating blindly, while at the caudal extremity of the left ventricle the atrioventricular canal opens, which is formed by the infolding of the muscular wall, corresponding to the atrioventricular constriction.

The septal wall l^etween the two lateral limbs at the caudal part of the ventricle is farther continued cranialward and is converted into wedge-shaped prominent ridges at the inner surface of the ventral and dorsal wall of the ventricle, in relation with longitudinal sulci on the external surface. These ridges have gradually disappeared within a caudal third of the ventricle (fig. 23). These prominent ridges show their anlage only on the ventral wall of the ventricle, near its caudal end, as seen in the previous stage. Consequently, there can be but little doubt that these folds cannot be regarded as the remnants of the primitive cardiac septum.



Fig. 22 Dorsal view of the reconstruction of an embryonic shield (stage VIII). Dorsal wall of the pericardium has been removed to show the pericardial cavity and myocardium, which is subdivided into several individual portions (bulbus cordis, ventricle, atrium, sinus venosus, etc.) by the distinct bulboventricular atrioventricular, sino-atrial constrictions. X 100.


The bulbus cordis is differentiated from the dorsal wall of the right ventricle near its cranial end, bulging out its wall cranial-dorsal and laterally. Its ventral wall is distinctly separated from the dorsal wall of the right ventricle at its cranial portion, projecting cranialward as an independent muscular sac, while in its caudal portion there can be noted no distinct demarcation between the wall of the bulbus cordis and that of the right ventricle. At the left and cranial sides of the bulboventricular junction, a deep external furrow can be seen, accompanied by a consequent infolding of the muscular w^all. On the right side the bulboventricular furrow is indefinitely marked only its cranial part, while in its caudal part it has disappeared entirely and insensibly continues into the dorsal wall of the right ventricle. On this account the bend of the heart tube at the bulboventricular junction is effected toward the right side, turning its concavity to the left side, beneath the left layer of the dorsal mesocardium.

On the dorsal surface of the bulbus cordis there can be seen a triangular intermesocardial space, its plane is directed dorsally and slightly to the left. Its apex is directed caudally and at a lower level, where the demarcation between the bulbus cordis and ventricle wall show indefinitely. Its base is situated cranially and at a higher level, where the wall of the bulbus cordis is distinctly demarcated from that of the ventricle, and there marks the cranial termination of the dorsal mesocardium. Both at the apical and basal portions the lateral mesocardial layers come to fusion.

A single myocardial tube of the atria begins at the atrioventricular constriction cranially and continues into the sinus venosus caudally, demarcated by the sino-atrial constriction. This muscular tube shows a marked asymmetry on both sides, for the left side, being decidedly expanded in all directions in comparison with the right side, just contrary to the ventricle, in which the right side is apparently more voluminous than the left side and bulges considerably caudolaterally. Moreover, this opposing asymmetry must be attributed partly to the normal obliciue direction of the atrioventricular constriction.


In consequence of this asymmetrical relation, the atrial tube forms a typical curvature with the ventricular limb at the atrioventricular junction, so that its convexity is directed toward the left side in the horizontal plane and ventralward in the vertical plane.



Fig. 23 Dorsal view of the reconstruction of the same embryonic shield (stage VIII) from which figure 22 was drawn. Dorsal wall of the pericardium and of the myocardium have been removed to expose the endothelium, which is subdivided into several individual portions in conformity with the myocardial subdivision. The two lateral endothelial tubes have fused and now communicate with each other throughout a middle third of the ventricle, but elsewhere they are separated. X 100.


The cranial extremity of the atria opens into the left ventricle through the atrioventricular canal, which is situated on the left side from the midsagittal line, for the right atrioventricular constriction is apparently more deeply infolded and proportionately the prominent ridge at the inner wall is strongly projected into the canal on the right side. The caudal extremity of the atria is continued into the sinus venosus, which diverge from each other into the two lateral myocardial tubes in relation with the foregut opening. The demarcation of these different portions is indicated by the sino-atrial constriction, of which on the left side the myocardial wall is more deeply infolded than on the right side.

The two lateral layers of the dorsal mesocardium are fused together from a middle third of the ventricle to the cranial part of the atria; they are in close contiguity at the atrioventricular constriction, in which region the dorsal mesocardium is beginning to disappear in an embryo slightly older than that of this stage. But at the portion of the bulbus cordis and the caudal part of the atria, the layers of the dorsal mesocardium have not come in contact. The arterial opening is disposed nearly vertically, but slightly to the left side, through which the endothelial tube comes from the myocardial cavity, while the venous opening is disposed dorsocaudally and assumes an irregular triangular space. Its base is situated caudall}^ and \entrally opposite to the foregut opening, as a result of which the layers of the dorsal mesocardium divert together with the corresponding muscular tubes, which continue caudally. Its apex of the venous opening is directed cranialward and Ues at the higher horizontal level. Through this intermesocardial space the enclosed endothelial tube can be seen.

On the ventral surface the myocardium is reflected onto the ventral wall of the pericardium at the sinus venosus. Here it can be observed that the mesodermal cells have proliferated to form an appreciable thickening around the endothelial tubes, indicating the future septum transversum.

The lateral endothelial tubes are fused in the middle third of the ventricle to the extent of fifteen sections. In this part they communicate with each other and the endothelial cavity is considerably dilated (fig. 23). This craniomedian part of the endothelial tube is bifurcated into the two cranial horns and two caudal prolongations. The cranial horns extend symmetrically from the cranial wall for a short distance on both sides and terminate blindly opposite to the cranial myocardial extremity of the ventricle, which is of conical form.

The right caudal prolongation is given off from the right side of its caudal wall and terminates as a short conical projection; its apical terminus is directed opposite to the caudal extremity of the right ventricle, conforming with it. The left caudal prolongation is given off from the left side of its caudal wall and caudally connects with the endothelial tubes of the atrium. These separate from each other and continue farther caudalward. From the origin of this left caudal prolongation caudally to the atrioventricular canal, that is, in the caudal part of the left ventricle, the two endothehal tubes show their smallest size and are very close in contact in some places, while in others the}- separate into two quite independent tubes with complete walls. Opposite to the atrioventricular canal the two endothelial tubes above mentioned begin definitely to separate into two lateral atrial endothehal tubes, increasing their calibers gradually caudalw^ard, while they lie approximately in a parallel direction.

The caudal extremities of the atrial endothelial tubes continue immediately into the endothelial tubes of the sinus venosus and then into those of the vitelline veins. The transition from the atrial endothelial tubes into those of the sinus venosus is marked by a sudden diminution in their diameter together with the general decrease of their cahbers and the abrupt lateral divergence of their course, due to the intervention of the foregut opening. These transitional points correspond to the external groove of the sino-atrial constriction.

In the ventricle the endothehal tubes are separated from the myocardial wall by a wide intervening space. In the atrium the intervening space becomes considerably narrower, and finally in the sinus venosus the endothehal tubes are enclosed intimately by their own independent myocardial wall, so that no appreciable space can be seen.

The endothelial tube of the bulbus cordis extends from the dorsal surface of the right ventricular endothelium as its continuous prolongation. This endothelial tube proceeds at first dorsocranially and then slightly toward the left side. This is enclosed by the corresponding myocardial wall of the bulbus cordis, which is closed cranially, but caudally opens and communicates with the ventricular cavity, as already mentioned. The right ventricular endothelium, which gives off the endothelial tube of the bulbus cordis, is fused together with the left one, but the left part of the fused ventricular endothelium participates in no way with the bulbus cordis.

The endothelium of the truncus arteriosus continues farther dorsally and slightly toward the left side from the bulbus cordis and passes through the above-mentioned arterial opening, and then bifurcates into lateral symmetrical branches, which are located between the foregut floor and the lateral dorsal mesocardial layers and continue farther cranially into the ventral aortae.

The first aortic arch and the ventral aortae are completely formed and the dorsal aortae are considerably elongated caudalward.

Summary and Conclusion

In our observations the first sign of the formation of angioblasts is shown in stage I, embryo A, in which neither the head fold nor the anlage of the pericardial cavity has yet appeared.

On the ventral surface of the mesoderm of the splanchnopleura of the cranial portion, cell bands first begin to separate, which separation is more advanced in the embryos B and C. These cell bands are regarded as angioblasts and they are frequently found to adhere to the indented and loosened mesoderm of the splanchnopleura by broader or narrower protoplasmic bridges. It has frequently been pointed -out that mitotic figures are found in the mesoderm of the splanchnopleura in the neighborhood of angioblasts. Furthermore, in many cases where the angioblasts are in close contact with the mesoderm of the splanchnopleura, it is impossible to discriminate the angioblasts from the mesodermal cells of the splanchnopleura, as concerns their sizes, forms, staining reaction, and the form of the nuclei, while a great difference can readily be recognized between the angioblasts and the adjacent entodermal cells. These findings show that in the genetic origin the angioblasts for the future endocardium are derived directly from the mesoderm of the splanchnopleura. The origin of the angioblasts from the mesodermal cells continues until a later stage, in which the greater part of the endotheUal tubes are already differentiated from the angioblasts in the anterior portion of the embryo, but the origin of the angioblasts can be recognized in the posterior part of the embryo, as is shown in the embryo of stage III.

In their well-known work on pericardial development, Strahl and Carius found it impossible to decide whether the embryonic coelom in the guinea pig appears at first in the region of the heart anlage, proceeding forward into the pericephahc mesoderm, or whether it begins first in the pericephalic mesoderm and then spreads out caudall}^ They speak as follows: Doch konnen wir augenblicklich eine ganz sichere Entscheidung nicht geben." The cause of this ambiguity is that they began their investigation of the origin of the intraembryonic coelom at too late a stage.

For the dog, Bonnet states that, concerning the origin of the intraembryonic coelomic space, that the lateral pleuropericardial cavities, having already distinctly appeared, anticipate the formation of the pericephahc space. To quote Bonnet directly: Eine ebensolche Spaltung des Mesoderms fiihrt in VHIo gleichzeitig im Bereiche des Herzwulstes zur Bildung der PleuroPericardialhohle. Ihre zuerst paarig angelegten spalten vergrossern sich, vereinigen sich nach vorne und bilden so ein nachhinten offenes Hufeisen; den pericephalen und lateralen Teil der Pleuro-Pericardialhohle. ' '

In our specimens, embryo C, stage I, show^s the discontinuous formation of the intraembryonic coelomic spaces in the cranial portion of the embryonic shield, as also in the pericephalic mesoderm, these spaces beginning as multiple foci. But they are primarily absent in the middle portion of the pericephalic mesoderm.

In stage II, in which the head fold of the embryo begins to separate from the surrounding blastoderm and the foregut has just begun to develop, the intraembryonic coeloniic space spreads out cranially into the pericephaUc mesoderm, cleaving the mesodermal layer in such a way, that the lateral primitive pericardial cavities communicate with each other. In a just sHghtly younger embryonic shield than this, each lateral pericardial cavity has progressed cranially into the pericephalic mesoderm, showing in this place a sht-hke space, which however, is divided by a thin mesodermic bridge in the middle line.

The pericardial cavity, therefore, commences simultaneously in the multiple foci, separating irregularly by mesodermal bridges throughout the lateral plate in the cranial portion of the embryonic shield and in the pericephalic mesoderm. These multiple coelemic spaces become confluent to form a single pericardial cavity, having an inverted-U shape, when the mesodermal bridges at the middle line of the pericephalic mesoderm have ultimately disappeared and, in consequence, at this time the bilateral pericardial cavities, already widely confluent, communicate from side to side (stage II, A). In this embryonic shield relatively wide endothelial tubes are differentiated only in the region of the hindbrain plate, where the pericardial cavity is wide open and the mesoderm of the splanchnopleura is thickened, projecting into the pericardial cavity as a prominent fold. In the pericephahc portion of the mesoderm, however, the pericardial cavity is seen merely as a lineal cleavage. Here a few angioblasts are scattered between the slightly thicker mesoderm of the splanchnopleura and the underlying entoderm.

In stage III the bilateral myocardial folds become quite prominent, so that in the region of the hindbrain plate they have been almost converted into the myocardial tubes, and enclose the well-developed endothelial tubes.

The formation of these myocardial folds has progressed cranialward opposite to the foregut opening on the left side. At the same time the endothelial tube becomes gradually thinner cranialward and terminates slightly caudad to the foregut opening. On the right side the formation of the myocardial folds proceeds still farther cranially into the caudal part of the craniomedian end of the pericardial cavity, where the thicker mesoderm of the splanchnopleura is raised from the underlying entoderm and in the space between them a number of angioblasts are distributed. On the right side the endothehal tube terminates cranially just opposite to the foregut opening. In front of the cranial termination of the lateral endothehal tubes a number of angioblasts are scattered, so that the cranial extremities of the endothehal tubes are nearly connected with each other through these angioblasts.

The cranial extremities of the lateral myocardial folds have not yet come to complete confluence, as the mesoderm of the splanchnopleura, shghtly cephalad to the cranial extremity of the left myocardial fold, remains still in loose contact with the underlying entoderm. If this portion of the mesoderm of the splanchnopleura were completely raised from the underlying entoderm, forming the myocardial fold, then the myocardial anlagen would come into confluence.

The most prevalent opinions with regard to the mode of the formation of the unilateral myocardial heart anlage from the bilateral myocardial tubes agree that, as above described, the bilateral myocardial tubes, at first independently, come to actual fusion with each other, and then the septal wall between them is absorbed secondarily, thus forming a single myocardial cavity. Our specimens show that the formation of the myocardial folds does not occur synchronously throughout the pericardial cavity, as in the region of the hindbrain plate they first appeared and developed considerably, while in the craniomedian limb of the pericardial cavity the formation of the myocardial folds was just starting and rising slightly from the underlying entoderm. However, the communication of the lateral myocardial tubes is accomplished when the formation of the myocardial folds is completed in the craniomedian limb of the pericardial cavity, in which region the formation of these folds occurs last. For this reason, the cranial prolongation of the lateral myocardial tubes has not been brought about by the direct extension of the first part of the myocardial tubes, but by the continuous progressive differentiation into the craniomedian limb of the pericardial cavity. Therefore, the confluence of the myocardial tubes into a single myocardial cavity is not' accomplished by the actual fusion of the bilateral myocardial tubes, followed by absorption of the septal walls.

In stage IV the formation of the myocardial fold is completely accomplished in the craniomedian limb of the pericardial cavity, elevating the mesoderm of the splanchnopleura from the underlying entoderm and projecting into the pericardial cavity. Both lateral myocardial tubes communicate with each other in this region.

Both the myocardial tubes are quite voluminous. They dilate in all directions, especially in their cranial portions, and they gradually reduce their dimensions caudal ward. On the surface of these transitions no distinct demarcation can be noted.

The two lateral endothelial tubes are well developed, lying side by side together in the portion of the confluent myocardial cavity, and here independent, intermediate endothelial cells are scattered between the lateral endothelial tubes.

In stage V the cranial portions of the two lateral myocardial tubes show^ much more dilatation and elongation, as their extent from the foregut opening to the cranial extremities considerably increases. But their confluent part still remains short. The transition from the cranial dilated myocardial tubes to their caudal slender portions is marked by a distinct annular atrioventricular constriction, which appears clearly first in this embryo.

A number of workers declare that the lateral myocardial tubes are subdivided into many individual portions by the demarcations prior to the fusion of the lateral myocardial tubes; in the chick, Duval, '99; in the cat, IMartin, '02; in the rabbit, KoUiker, '84. Kolliker states, Ein Herz aus diesem Stadium ist sehr verschieden von dem primitiven Herzen eines Hlihnerembryo, was einfach darin begrundet ist, dass, wie bemerkt, bei Saugethieren schon vor der Verschmelzung der beiden Herzhiilften die drei Herzabschnitte angelegt sind."

Kollier declares in similar language: 'Mn den beiden Herzrohren ist aber kurz vor ihrer Vereinigung schon eine Gliederung bemerkbar."


In our specimens this embryo shows first the atrioventricular constriction, even though in the previous embryo two myocardial tubes were already confluent into a single myocardial cavity.

The two lateral endotheUal tubes are considerably developed, especially in the confluent portion of the myocardial cavity, where they approach each other almost to contact. From the atrioventricular constriction caudalward the two endothelial tubes assume an abruptly narrow caliber, thus distinguishing the larger cranial ventricular from the smaller caudal atrial portion. In tracing farther caudally, no demarcation can be detected on them.

In stage VI the confluent myocardial cavity increases especially in the craniocaudal extent. The cause of this may be attributed partly to the retirement of the wedge-shaped septal ridge cranialward, which had projected into the confluent myocardial cavity, as the conversion of the inner walls of the cranial lateral mj^ocardial extremities, and partly to the active backward progress of the foregut opening. Approximately, in the whole extent of the ventricle and in the cranial part of the atria the two lateral mj'ocardial cavities communicate with each other and these two myocardial portions are demarcated sharply by the atrioventricular constriction. In the middle third of the ventricle the two lateral endothelial tubes are actually fused and communicate with each other for a short distance. At the atrioventricular constriction the calibers of the two endothelial tubes are considerably reduced and, as we proceed still farther caudally, they are again gradually increased in diameter.

In an embryo of Perameles nasuta having fifteen to sixteen somites, ]Miss Parker pointed out that the fusion of the lateral endothelial tubes first took place. The fused portion already extends throughout about eighteen sections. She states that from this portion the bulbus cordis is derived.

Wang reports concerning a ferret embryo, having thirteen to fourteen somites, that the two endothelial tubes had united in a part of their extent. The fused portion, extending throughout about sixteen sections, appeared to be the ventricular part.

In our specimens this embryo shows first the fusion of the two lateral endothehal tubes throughout only seven sections, having a 5 /x thickness, and this united part corresponds to a middle third of the ventricle and lies precisely on the midsagittal plane. In the guinea pig the fusion of the lateral endothelial tubes takes place at a relatively early stage of development — a stage in which in the myocardial and endothelial tubes there can be distinguished simply the ventricular and atrial portions. In the above-mentioned animals investigated by other authors, the fusion of the lateral endothelial tubes was first noted in the relatively older embryo, in which the different parts of the myocardial and endothehal tubes are already definitely subdivided. JMoreover, their embryos show that the fused portion is considerably extended in comparison with this embrj^onic shield.

The factors which are generally accepted as the cause of the loop formation of the endothelial tubes depend on the fact that the rate of growth of the two endothelial tubes exceeds that of the pleuropericardial cavity. Bonnet depicts a dog embryo in which the primary subdivision of the endothelial tubes into sinus venosus, atrium, and ventricle has occurred before they have fused to form a single myocardial cavit}'.

Wang pointed out the loop formation with the subdivision of the heart (atrium, ventricle, bulbus, etc.) in the ferret embryo, before the endothelial tubes had become fused.

But in our specimens there is no loop formation, nor can the subdivision of the heart be marked out on either of the endothelial tubes before they are fused together, even though the ventricle and atrium may be roughl}^ distinguished by their difference in size.

Contrary to the above-mentioned assumption that the loop formation of the endothelial tubes has been brought about, the moment of fusion of the two lateral endothehal tubes shows quite other facts in the guinea pig. In the embryonic shield at this stage of development the confluent part of the myocardial tube grows excessively in the craniocaudal direction and decreases its lateral width in comparison with the embryo of stage V, as measured and compared on both reconstruction models which had been magnified to the same degree. Consequently, the two endothehal tubes are brought together in the median plane, where they come to fusion, by the extreme longitudinal stretching of that part of the myocardial tube in which the endothelial tubes are enclosed. Concurrently, the active dilatation of the two endothelial tubes plays a part in bringing about the fusion, which takes place first in the most dilated portions.

In stage VII the myocardium presents cranially a single expanded craniomedian extremity, assuming a sac form, and here represents the ventricle, while caudally this myocardial sac is bifurcated into two rather slender myocardial prolongations. Their demarcation is indicated by the well-developed atrioventricular constriction sUghtly cephalad to the foregut opening. The transition from the atrium into the sinus venosus is marked by an indefinite indentation on the bilateral myocardial tubes caudad to the foregut opening and slightly more distinct on the left side. Corresponding to these myocardial constrictions, there can be pointed out a similar indentation on the endothelial tube on the left side.

The two lateral endothehal tubes are fused together in the cranial two-thirds of the ventricle, and its cranial extremity is terminated as a single conical apex opposite to the cranial end of the myocardial ventricle. In tracing farther caudalward from this united portion, the two endothelial tubes are separated.

In this stage of the development the myocardial and endothehal heart anlagen of the ventricle present a considerable asymmetry, due to the unequal growth of the individual parts, despite the fact that, in the embryonic shields prior to this stage of development, the heart anlagen are shown as a practically symmetrical development on both sides, even after the fusion of the lateral endothelial tubes has already been accomphshed.

jMiss Parker describes the heart of the Perameles obesula stage V as follows: In the ventricular region of the heart, the right and left endothelial tubes are approximately equal in size, but where there is an inequality the right is the larger."

In the ferret embryo Doctor Wang says: "It has been found that the two tubes, prior to fusion, appear to have been shifted as a whole toward the right side and that they remain in this position even after partial fusion has taken place.' '

In our specimens the myocardial asymmetry of the ventricle is attributed partly to the extraordinary bulging of its right wall dorsally, laterally, and slightly caudadly, and partly to the deeper infolding of the myocardial wall of the atrioventricular constriction of the right side. In the ventricle the endothehal tubes are much more dilated on the right side than on the left throughout its whole length, regardless of the fused or nonfused portions, and it expands considerably dorsally, laterally, and caudadly. Consequently, they deviate from the middle plane toward the right side and are situated more to the right side of the myocardial ventricle. The right endothelial tube is elongated dorsally at the caudal third of the ventricle, where the two lateral endotheUal tubes, being separated, pass through the intermesocardial space vertically. From this portion the bulbus cordis develops in a later stage; its termination is cranially bifurcated into two lateral endothelial branches, which continue farther cranialward into the ventral aortae.

In stage VIII there are present three distinct constrictions on the tubular myocardial surface, infolding the whole thickness of the myocardial wall into the mj^oeardial csLvity. Consequently, the myocardium can be subdivided by very distinct demarcations into the bulbus cordis, bulboventricular constriction, ventricle, atrioventricular constriction, atrium, sino-atrial constriction, and sinus venosus in the craniocaudal succession.

The bulbus cordis is demarcated from the dorsal wall of the expanded right ventricle at its cranial end by the horizontal bulboventricular constriction. The bulboventricular constriction shows considerable asymmetry, making a deeper furrow on the external surface of the mj^ocardium at the left and cranial sides, while at the right side it is present as a shallow depression on the external surface, diminishing imperceptibly caudalward, until it has entirely disappeared at the part of the right ventricle. Thus neither external furrow nor infolding of the myocardium is shown along the caudal boundary of the bulboventricular junction, and here the wall of the bulbus is directly continuous into that of the right ventricle. Corresponding to the external view, the deep infolding of the myocardial wall as the inner prominent ridge is shown at the left and cranial sides of the bulboventricular canal, while on the right side it can be recognized only cranially and disappears insensibly caudalward. In this fashion the curvature of the myocardium at the bulboventricular junction is effected in such a vray that its convexity is turned toward the right side. On the dorsal aspect of the bulbus cordis there is a triangular intermesocardial space disposed vertically and sHghtly toward the left side, through which the truncus arteriosus passes out from the myocardial cavity up to the floor of the foregut.

The atrioventricular canal is well marked and is disposed approximately in the vertical plane. It is produced by the infolding of the myocardial wall, which is deeper and more caudad on the right side than on the left. Consequently, the opening of this canal is situated on the left side of the middle plane. In this relation the myocardial tube forms a marked curvature at the atrioventricular junction, turning its convexity toward the left side and ventralward, with the result that the ventricular portion lies at the right side and slightl}^ ventrally to the atrial portion. This curvature is remarkably accentuated in the next stage of the development, in which, for a short extent, the dorsal mesocardium disappears at the atrioventricular junction and herewith the ventricle comes to the ventral surface of the atrium, being free from the restriction of the dorsal mesocardium.

The ventricle can be divided incompletely into two hmbs by the ventral and dorsal longitudinal sulci. At the caudal part of the ventricle, for a short distance, the two hmbs are divided into two completely independent cavities by the septal wall. The caudal extremity of the right ventricle terminates bUndly as a conical process and it projects caudolaterally.


In the literature I could not find a description of this. On first observation it seemed to me that the septal wall and its conversion into prominent ridges at the inner surface of the ventral and dorsal myocardial wall were produced by the actual fusion of the two lateral myocardial tubes. Therefore, this may account for the remnant of the primitive myocardial septum. But in the embryos of stages VI and VII there was present no septal wall nor prominent ridge similar to this in their single ventricle, in which they would be more distinctly present if they accounted for the production of the actual fusion of the lateral myocardial tubes and the remnant of the primitive cardiac septum.

Accordingly, it appears to be due to the fact that the caudal surface of the myocardial ventricle on the right side is projected actively backward by the unequally excessive rate of growth in this portion, while in the middle plane a part of the myocardial wall does not proportionately accompany this active backward growth, but remains as the septal wall. <