Talk:Paper - The fate of the ultimobranchial bodies in the pig (1918)

THE FATE OF THE ULTIMOBRANCHIAL BODIES IN THE PIG (SUS SCROFA)

J. A. BADERTSCHER

Deparlmenl of Anatomy, Indiana University School of Medicine, Bloomington,

Indiana

FOUR PLATES

I. Introduction ^ ' 89

II. Historical 90

III. Material and methods 92

IV. Description of stages 93

V. Summary and discussion Ill

VI. Conclusions 119

VII. Bibliography 121

I. INTRODUCTION

The fate of the ultimobranchial bodies is one of the many unsettled questions associated with the development of the thyroid gland. While most of the results of the considerable amount of investigation that has been done in recent years on these structures in various mammalian species have led to the interpretation that they do not contribute to the structural elements of the thyroid gland, there is still a diversity of views as to their actual fate. The variety of views expressed in the literature in regard to their fate in mammals is apparently due to several factors among which may be mentioned: (1) the possibility of a variable developmental behavior of these structures in different mammalian types, (2) inadequate series of successively older embryonic stages (especially embryos of larger mammals) , and (3) faulty technique (principally poor fixation of the thyroid gland in the older embryos of the larger mammals, especially man).

1 Some of the younger stages used in this study were prepared during the summer of 1914 while a guest in the Department of Histology and Embryology in Cornell University. I wish to express my appreciation to Prof. B. F. Kingsbury for the facilities so generously extended to me during that time.

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A study of the ultimobranchial bodies in a wide range of successively older developmental stages of pig embryos of which the thyroid gland was well fixed, has resulted in bringing to light some interesting and important developmental features of these structures in this mammalian type.^

II. HISTORICAL

A brief historical outline representing in a general way the different views in regard to the fate of the ultimobranchial bodies is here given. The works of Verdun ('98) and Grosser ('12) render an extensive bibliography in this article unnecessary.

Born ('83) claims for the thyroid in the pig a triple origin. In a 21 mm. embryo he finds that the nuclei and cytoplasm of the cells composing the lateral thyroids stain more intensely than the cells of the median thyroid, but in a 37 mm. embryo in which the lateral thyroids have become imbedded in and fused with the median thyroid there is no histological difference between these structures and the median thyroid.

According to Moody ('12) in pig embryos 100 mm. in length no difference is to be observed between the central and lateral parts of the gland in vascularity, colloid formation or connective tissue development." He believes that the ultimobranchial bodies contribute to the structural elements of the thyroid gland.

Simon ('96) claims that in mammals (guineapig, rabbit, cat, calf, sheep, and pig) the lateral thyroids do not actually fuse with the elements of the median thyroid, although they become entirely inbedded in the latter. The lateral thyroids in early developmental stages show signs of growth and further development. During this period, which he designates the periode d'activite, the lateral thyroids are broken up into cell cords and cell

^ No consideration was given to the origin of the structure variously termed 'ultimobranchial body,' 'postbranchial body,' 'suprabranchial body,' 'telqbranchial body,' and 'lateral thyroids.' The morphological value of these terms have been discussed by Greil ('05), Rabl ('09), Kingsbury' ('14), and others. Throughout the descriptive part of this work the term 'ultimobranchial body' will l^e used.

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masses. This is brought about in an entirely passive way, by the ingrowth of vascular tissue and of elements from the median thyroid. These cell cords and cell masses stain more intensely than do the elements of the median thyroid. Traces of the lumen persist mainly in the more central part of the lateral thyroids. These structures in later developmental stages undergo degenerative changes. This period, which he designates the periode de survivance, is characterized by a disappearance of the cell cords and the degeneration of the more centrally located epithelial cells, forming cysts lined with cuboidal or columnar epithelium which may or may not be ciliated. He also claims that the formation of cysts in the lateral thyroids of pig embryos is not a constant occurrence. Cysts in these structures in the pig were found only in five out of eleven embryos which he examined. In a 210 mm. embryo, the largest examined, no traces of the lateral thyroids were found. He is of the opinion that these structures in the pig disappear entirely.

Rabl ('08) finds that in the older mole embryos the lateral thyroids are reduced to insignificant structures, being represented by cell cords and cysts.

Verdun ('98) finds that in birds (chicken and duck) the postbranchial bodies remain independent structures of a glandular character but do not produce colloid. He regards these structures as special glands for birds. In the thyroid of mammals (rabbit, cat, dog, mole) the postbranchial bodies are represented by cysts and cell cords. The cysts vary greatly in size in the different species studied. Neither during the embryonic nor the postnatal life of these mammals was he able to demonstrate the transformation of the epithelial cords of the postbranchial bodies into thyroid follicles. He beheves that the cysts and cell cords represent atrophied vestiges of the special gland in birds.

According to Tourneaux and Verdun ('97) the lateral thyroids in human embryos can for some time be recognized as a rather densely staining mass on the posterior surface of the lateral lobes of the thyroid gland. They undergo the same structural changes as the median thyroid, but more slowly. From the

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median thyroid anlage, however, is derived the larger part of the structural elements of the thyroid gland.

According to Christiani, in rodents (rat) the lateral thyroid gives rise to an epithehal body.^

Maurer ('99) finds that in the Echidna the postbranchial bodies do not fuse with the median thyroid anlage. In the adult condition the thyroid lies posterior to the postbranchial bodies. The latter are represented by two alveolar structures which developed colloid (judged by staining reaction). The first traces of colloid formed in the postbranchial bodies appears, however, in later developmental stages than does that of the median thyroid.

Prenant ('94) finds that in sheep embryos the lateral thyroid develops into a central canal with an irregular lumen from the walls of which cell cords and cell masses (recognized by their dense structure) extend into the substance of the median thyroid. An intimate fusion takes place between the lateral and medial elements. In later developmental stages the tissue, which in earlier stages can be recognized as derived from the lateral thyroids, disappears. He was unable to determine whether or not the lateral thyroids contribute to the structural elements of the gland.

In this brief historical sketch the following views as to the fate of the ultimobranchian bodies were brought out : (1) They contribute to the structural elements of the thyroid gland; (2) They develop into cysts; (3) They develop into a gland of a different structure from that of the thyroid gland; (4) They develop into epithehal bodies, and (5) They disappear entirely.

III. MATERIAL AND METHODS

The material used for this investigation was collected in great abundance at a packing house. The upper jaw, cranium, and thorax were removed from embryos ranging from 15 to 25 mm. in length. The part containing the thyroid was thus made comparatively small and fixed well. From embryos 26 to 75 mm. in

» Cited from Zuckerlandl ('03).

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length only the neck, from which the sides and the cervical vertebrae were removed, was reserved. From embryos 100 to 270 mm. in length (full term) only the thyroid with some of the surrounding structures — trachea, esophagus, a portion of the thymus, etc., was removed. The length in millimeters of the different developmental stages of which the thyroid was prepared for a study of the ultimobranchial bodies is as follows: 15, 16, 17, 17, 18, 18, 19, 19.5, 20, 20, 21, 21, 21.5, 22, 22, 23, 23, 23, 24, 24.5, 25, 25, 26, 27, 27, 28, 29.5, 30, 33, 35, 37.5, 38, 40, 48, 53, 60, 65, 65, 75, 100, 100, 111, 125, 125, 145, 150, 160, 175, 225, 245, 270, and 270. These figures represent the length of the embryos while in a fresh condition.

The fixing fluids employed were Zenker's fluid, Zenker-formol, and Picro-aceto-formol. The materia) was imbedded in paraffi.n. The earlier embryos were cut transversely in sections 5 microns thick, while those of later stages in sections 8 to 10 microns thick. Various stains were used. For embryos 15 to 65 mm. in length, iron hematoxylin gave the best results. The thyroid gland of later developmental stages was stained with Chloral hematoxylin and eosin, and eosin-methylene blue.

IV. DESCRIPTION OF STAGES

The earliest stage chosen for description is one just before the ultimobranchial bodies have fused with the thyroid gland. 'These structures will be described in two embryos of the same size only when there is a marked contrast in their size, structure, or position in the thyroid in the two embryos.

Embryo of 18 mm. (fig. 1). The ultimobranchial bodies have lost their connection with the fourth (?) pharyngeal pouch and extend cephalad beyond the anteror margin of the thyroid gland. Their anterior portion is in form a slender tube, ovaF in cross section, and with wall two to three layers of cells (nuclei) thick. Caudalward the walls of these structures gradually becomes thicker. In the portion in relation to the thyroid gland the lumen in places is obliterated and the remnants persist as mere slits. Anteriorly the surface of these tubules is quite smooth, while caudal] y irregularities occur on their surface. Their cau

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dal halves lie at varjdng distances dorsal to the lateral margin of the thyroid gland which has the general shape of a crescent with its horns directed anteriorly and dorsally. In a few sections they are separated from the thyroid only by a very thin layer of connective tissue iU). They extend almost to the caudal margin of the thyroid gland. Their caudal ends lie more closely together than their anterior ends.

The ultimobranchial bodies at this stage are composed of a syncytium. No cell walls are present. Vacuoles are found throughout their entire extent, although their distribution is not uniform. In places they can be found throughout an entire cross section of an ultimobranchial body while in other places they are confined to its more central portion. The vacuoles vary in size, the largest being almost as large as some of the nuclei.

The nuclei vary somewhat in size and in shape. Some are oval, some round, while others are irregular in outline. They contain from one to three nucleoli and a rather generous amount of chromatin which is in the form of granules and threads. The more centrally located nuclei have no regular arrangement while those near the periphery are in places quite regularly arranged. They are more closely packed together in the nonvacuolar than in the vacuolar portions of the ultimobranchial bodies. A consideration of this feature is of particular importance in stages in which the ultimobranchial bodies have fused with the thyroid gland. Mitoses of the nuclei can readily be found, especially in the larger more caudal part of the bodies, thus indicating a growth tendency of these structures. Neither blood vessels nor connective tissue are present in the ultimobranchial bodies at this stage.

The thyroid {T) is composed of nonvacuolar cell masses and cell cords^ the latter of which are for the most part transversely arranged. No cell walls can be demonstrated, hence the cell

■* Norris ('16) finds that in early developmental stages of human embiyos the cell cords seen in cross sections of the thyroid gland represent in reality sections of fenestrated epithelial plates. As I have not made a careful study of the formation of the follicles in the thyroid gland I shall use the term 'cell cords' which is the microscopic picture presented in cross sections of the gland.

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cords and cell masses have a syncytial structure. The nuclei vary in shape and somewhat in size but their form, average size, and structure in this stage is the same as in the ultimobranchial bodies. The nuclei of the thyroid are more closely packed together than in the vacuolar portions of the ultimobranchial bodies, but when a nonvacuolar portion of the latter is brought into the same microscopic field wdth a portion of the thyroid gland, no difference in structure can be seen between them even under high magnification (1500 diameters). Some of the spaces between the cords of cells are lined with endothelium and contain blood.

Embryo of 19.5 mm. (figs. 2 a and 2 b). The ultimobranchial bodies extend slightly farther cephalad than the thyroid gland. Only slight traces of their lumen still persist. They lie along the dorsal surface of the thyroid gland but are located nearer the mesial plane than those of the preceding stage. In some places there is actual fusion between these structures and the thyroid gland (fig. 2 a, right side), while in other places a thin layer of connective tissue intervenes (fig. 2 a, left side). The ultimobranchial body on the left side extends almost to the caudal margin of the thyroid gland (fig. 2 b), w^hile on the right side it terminates twelve sections (5 microns in thickness) earlier. The shape and orientation of the thyroid gland is similar to that in the preceding stage.

In this stage, as in the preceding one, both vacuolar and nonvacuolar areas are found in places along the periphery of the ultimobranchial bodies. In some places where actual fusion has taken place wdth the thyroid gland it is impossible to tell w'here the two striictures meet. Fusion with the thyroid gland has taken place along the ventro-lateral surface of the ultimobranchial bodies. The dorso-medial surface of these structures is in places studded with epithelial buds (fig. 2 a) .

In the ultimobranchial bodies of this developmental stage are found a few nuclei in which the nucleoplasm stains quite deeply in comparison with that in the large majority of nuclei present. In some of these nuclei the chromatin is more abundant than in the more numerous and more lightly stained ones but in both

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types of cells it is distributed in the form of threads and granules. With comparatively low magnification they appear as dark specks among the other nuclei (fig. 2 a). Since these have apparently been regarded by some investigators as degenerating nuclei, they deserve special attention in successively older developmental stages.

Embryo of 20 mm. (figs. 3 a, 3 b, and 3 c). The uLtimobranchial bodies are small anteriorly, and extend slightly farther cephalad than the thyroid gland. The one on the left side is separated for a short distance from the extreme anterior part of the thyroid (fig, 3 a). Caudal ward these structures rapidly become larger and form the greater portion of the horns of the crescent shaped tripartite complex. The one on the left side is slightly larger, and eleven sections (5 microns in thickness) longer than the one on the right side and extends as far caudally as does the thyroid gland. The extreme caudal portion of these structures is not fused with the thyroid gland. Remnants of the lumen are present in two places in the anterior third of the left one.

A feature quite noticeable in the ultimobranchial bodies of this developmental stage is the presence of unusually small nuclei which are found in small groups and promiscuously scattered among those of usual size. From their similarity in structure to the larger nuclei they seem to be normal. Deeply stained nuclei, which are somewhat more numerous throughout these structures than in the preceding stage, are also present in these groups.

It is impossible to determine definitely the exact place of fusion between the ultimobranchial bodies and the thyroid gland. Judging, however, from the uniformity of the distribution of the deeply stained nuclei, from the absence of cell cords along the greater portion of their dorso-mesial free border, from the manner in which they terminate, as stated above, from the absence of blood vessels, and from the distribution of the small nuclei and vacuoles, it seems that the cell masses labeled ultimobranchial bodies in the figures 3 a, 3 b, and 3 c represent exclusively the ultimobranchial bodies.

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Epithelial buds, as represented in figure 3 b (Ep.B.), are present in various places along the free border of these structures. These buds are fused to the more or less vacuolar mass of cells. Mitosis can be found without much searching in both the ultimobranchial bodies and the thyroid gland.

Embryo of 21 nmi. (fig. 4). Both ultimobranchial bodies are as long as the thyroid gland. They are fused to the latter along their entire extent excepting the extreme caudal end of the left one which is separated from the gland by a thin layer of connective tissue. The one on the right side has a comparatively regular outline and makes up nearly all of the lateral portion of the tripartite complex ([/). The ultimobranchial body on the left side is more deeply embedded in the thyroid gland than the right one which makes it difficult to follow its extent in transverse sections. In places blunt and both vacuolar and nonvacuolar epithelial buds are attached to these structures.

Groups of small nuclei in the ultimobranchial bodies are present but they are not as mumerous as in the preceding stage. The darkly stained nuclei are no more numerous than in the previous stage. A few darkly stained nuclei were found in the cell cords of the thyroid gland. These have a structure similar to the darkly stained nuclei of the ultimobranchial bodies but are not nearly as numerous and can be found only after prolonged searching. Mitoses can readily be found in all the different components of the tripartite complex.

Embryo of 21.5 mm. (fig. 5). The ultimobranchial bodies lie along the entire extent of the dorso-medial margin of the thyroid gland and compose the largest portion of the tripartite complex. The anterior extremity of both ultimobranchial bodies and the posterior extremity of the left one are not fused with the thyroid gland. Their largest diameter (U) is about midway between their extremities from which they gradually taper to blunt points. Their greater portion is vacuolar but nonvacuolar areas are present in their deeper parts as well as along their periphery. Large blunt epithelial buds, some of which are vacuolar, are present in various places along their free border. The darkly

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stained nuclei and groups of small nuclei are more numerous than in the preceding stage.

Embryo of 22 mm. (figs. 6 a and 6 b). The tripartite complex presents extremely varied pictures. Its anterior fourth is composed entirely of typical thyroid cell-cords while its caudal portion is composed chiefly of the ultimobranchial bodies (fig. 6 b) . The caudal portion of each ultmiobranchial bodj^ is composed of a cell mass of irregular outline in which remnants of the lumen, lined with columnar epithelium, still persist (fig. 6 b, L). Anteriorly, they are largely broken up into coarse cell cords which process marks the beginning of important developmental features in these structures (fig. 6 a, U). Nonvacuolar areas can be found throughout their entire extent. The deeply stained nuclei in the coarse cell cords, in the more central unbroken masses, and in the epithelial buds are more numerous than in any of the preceding stages. They can be quite readily found in the cell cords of the thyroid gland (figs. 6 a and 6 b), but are not nearly as numerous as in the ultimobranchial bodies. No degenerating nuclei, such as pyknotic or fragmented nuclei, were found. Small nuclei, in groups and diffusely scattered, are more numerous in the ultimobranchial bodies of this stage than in the previous one. In another 22 mm. embryo the size, shape, and extent of the ultimobranchial body along the thyroid gland is quite similar to that of the 21.5 mm. embryo described above.

Embryo of 23 mm. (figs. 8 a, 8 b, and 8 c). The ultimobranchial bodies are small anteriorly and extend slightly farther cephalad than the thyroid gland. For a short distance anteriorly the ultimobranchial bodies and the thyroid are not fused. From their point of fusion with the thyroid they rapidly become larger so that the caudal portion of the tripartite complex is largely composed of the ultimobranchial bodies (figs. 8 a, 8 b, and 8 c, U). The epithelial buds attached to the ultimobranchial bodies are in general not as large as those in the 22 mm. embryo. The darkly stained nuclei and groups of small nuclei are also less numerous than in the preceding stage. Only an occasional darkly stained nucleus can be found in the cell cords of the thy

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roid gland. A few blood vessels of a capillary character are found in the larger portion of the ultimobranchial bodies.

Embryos of 24 to 30 mm. During this developmental period quite marked changes occur in the ultimobranchial bodies, the most pronounced of which is a breaking up of their major portion into cell cords which, when first formed, are usually larger than those of the thyroid gland. Two factors are apparent during the formation of cell cords, namely, a continued growth and division of the epithelial buds, and their invasion by mesenchymal and vascuolar connective tissue. The extent to which this process occurs during this developmental period varies. In some embryos these structures are almost entirely broken up into cell cords while in others a centrally located, more or less vacuolar and irregularly outlined core, variable in size, persists for some time longer. This process is illustrated in figure 9 (U), which represents a section through almost the middle portion of the tripartite complex in a 27 mm. embryo. In most stages of this developmental period (24 to 30 mm.), and even in some later stages, the caudal portion of the ultimobranchial bodies is for a time less broken up into cell cords than their more anterior part. Also, these structures never become entirely vacuolar. Some of the coarse cell cord^ are composed of a nonvacuolar syncytium. Nonvacular areas are also present in the more centrally located syncytial mass and in the larger and less unbroken caudal portion of these structures. Groups of small nuclei which appear normal in structure are preseilt in both vacuolar and non vacuolar parts. In places, instead of being arranged in groups, the small nuclei are quite uniformly scattered among the larger nuclei. Mitoses in both the thyroid gland and ultimobranchial bodies can readily be found.

It is during this developmental period and also in somewhat earlier and later stages that the darkly stained nuclei are most numerous. In only two developmental stages, namely, in a 23 mm, embryo (not the one described above), and in a 24 mm. embryo (fig. 7, D.N.), were degenerated (pyknotic and fragmented) nuclei found in sufficient numbers to .suggest a general degeneration of these structures. The degenerated nuclei in

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these stages were not generally distributed throughout the ultimobranchial bodies but were found in localized areas. A few darkly stained nuclei can be found in the cell cords of the thyroid gland during this developmental period. In the thyroid, however, they are never very numerous and in some they are found only after prolonged searching.

Embryo of 29.5 mm. (figs. 10 a, 10 b, and 10 c). The tripartite complex in this embryo is of interest in that a large portion of it is asymmetrical in shape, due to the unequal length of the ultimobranchial bodies. Nearly all of the anterior fourth of the complex is symmetrical and is composed of cell cords of the thyroid gland only (fig. 10 a). The greater portion of the middle two-fourths of the tripartite complex is characterized by the presence of massive cell cords of the left ultimobranchial body and the entire absence of the right ultimobranchial body (fig. 10 b). Along the posterior fourth of the thyroid gland both ultimobranchial bodies are present. The left one terminates rather abruptly thirty sections (150 microns) anterior to the caudal end of the thyroid while the right one tapers to a point and extends as far caudally as the thyroid gland. The extreme caudal portion of each ultimobranchial body is less broken up into cell cords than is represented in figure 10 c. Small disconnected vacuolar areas are present in the more caudal portion of both branchial bodies. The large cell cords are almost entirely free from vacuoles but are characterized by a comparatively large number of small nuclei. The deeply stained nuclei, which are comparatively few in number, are most confirfed to the ultimobranchial bodies. Only a few are present in the cell cords of the thyroid gland. Only a very few degenerated nuclei were found.

In embryos from about 30 mm. in length to stages in which colloid is first present in the folUcles of the thyroid gland (75 mm.), the ultimobranchial bodies present a varied appearance. They are largely broken up into cell cords and in the progress of development the cell cords of the thyroid gland and usually those of the ultimobranchial bodies have become closely packed together so that a sharp demarcation between the

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median and lateral elements of the tripartite complex is not always evident. A description of a few stages will suffice to bring out the general character of the ultimobranchial bodies during this developmental period. Since the thyroid gland in previous stages is free from vacuoles, it is, I believe, safe to assume that the vacuolar areas found in the succeeding stages represent portions of the ultimobranchial bodies.

Embryo of 33 mm. The ultimobranchial bodies are limited to the posterior half of the tripartite complex. They are located on each side of the median plane, deeply buried beneath the dorsal surface of the thyroid gland and are represented by disconnected vacuolar areas the majority of which are not sharply circumscribed but gradually give place to the compactly arranged cell cords of the thyroid gland with which they are fused. The thyroid terminates posteriorly in two short blunt processes. In these processes small vacuolar areas are promiscuously scattered among the cell cords. A few" small vacuolar areas which are round in cross section and sharply demarcated by connective tissue from the surrounding cell cords were also found. Only a few darkly stained nuclei are present. No degenerated nuclei were found.

Embryo of 35 mm. The only traces of the ultimobranchial bodies are small disconnected vacuolar areas on each side of the median plane of the thyroid gland. The gland terminates posteriorly in two short blunt processes of nearly equal length, both of which are partly vacuolar. Only a few deeply stained nuclei are present.

Embryo of 37.5 mm. The anterior portion of the tripartite complex is very large and strongly crescent in outline. Caudalward it gradually loses its crescent outline and ends in a single blunt cone-shaped process. The ultimobranchial bodies lie in the posterior four-fifths of the thyroid gland. Their anterior ends lie imbedded beneath the dorsal surface of the thjrroid lateral to its median plane. Caudal ward they rapidly increase in size and shift in position so that in places they extend to the free surface on the lateral margin of the thyroid gland. Their posterior ends are fused and compose by far the largest part of the

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caudal one-fifth of the tripartite complex. The greater portion of the ultimobranchial bodies are in the form of vacuolar syncytial cores which give off coarse cell cords. Some of the coarse cell cords are vacuolar and many are fused to the cell cords of the thyroid gland. The central core is more or less' invaded with mesenchymal and vascular connective tissue. Deeply stained nuclei are quite numerous in the. ultimobranchial bodies and a few are found in the cell cords of the thyroid gland. No degenerated nuclei were found. The variableness in the size of the nuclei in the ultimobranchial bodies is more marked than in the nuclei of the thyroid gland, the former having a proportionally larger number of small nuclei. The extent to which the transformation of the ultimobranchial bodies has taken place in this stage is about equal to that in the 29.5 mm. embryo.

Embryo of 38 mm. The ultimobranchial bodies are limited to the posterior two-thirds of the tripartite complex. Their anterior ends are small and entirely imbedded in the thyroid gland near its dorsal surface. Caudalward they rapidly increase in size. The tripartite complex ends in two blunt cone-shaped processes the greater portion of which are composed of the ultimobranchial bodies. The ultimobranchial bodies are composed of irregularly outlined syncytial cores which gradually merge into the compactly arranged cell cords, of the thyroid gland. Only a few capillaries are found in them. Mitoses in the vacuolar areas as well as in the cell cords of the thyroid are quite numerous. Only a few deeply stained nuclei are present. No degenerated nuclei were found.

Embryo of 40 mm. The ultimobranchial bodies lie in the posterior half of the thyroid gland. Their anterior parts are represented by small disconnected vacuolar areas which lie deeply buried in the thyroid gland lateral to its median plane. Caudalward these areas become large and branched so that the caudal fifth of the thyroid gland is largely invaded by a vacuolar syncytial mass which is not sharply demarcated from the closely packed cell cords of the thyroid gland. The tripartite complex ends in two blunt and slightly vacuolar processes of unequal length. A small number of deeply stained nuclei are present

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throughout the entire complex. Only a few degenerated nuclei were found in the vacuolar areas. There are realtively more small nuclei present in the vacuolar areas than in the non vacuolar portions and mitoses are more numerous in the latter than in the former areas.

Embryo of 48 mm. (figs. 11a and lib). Both ultimobranchial bodies extend anteriorly as far as the thyroid gland. The one on the right side is isolated from the anterior fourth while the one on the left side is isolated from the anterior third of the thyroid gland (fig. 11a, U). Excepting a vacuolar area present in the anterior end of the left one and traces of the lumen caudal to the vacuolar area, the isolated portions of the ultimobranchial bodies have a structure identical to that of the thyroid gland along which they lie. The right ultimobranchial body near its fusion with the thyroid is quite large (fig. 11a, U). The part fused to the thyroid gland is difficult to follow, yet traces of it may be seen in the form of small vacuolar areas that are promiscuously scattered beneath the dorso-lateral margin of the tripartite complex. Some of these areas are sharply outlined while others gradually merge into the compactly arranged cell cords.

The left ultimobranchial body caudal to its most anterior point of fusion with the thyroid gland is characterized in some places by very irregular vacuolar areas, while in other places by large, closely packed cell cords. In some places also it is only partially fused to the thyroid gland while in other places it is entirely separated from it by connective tissue (fig. 11 b, U.) Traces of the lumen still persist (L). The tripartite complex ends in two large conical processes which have, excepting a small vacuolar area found in each, a typically thyroid structure. Only a few darkly stained nuclei were found. Mitoses throughout the entire complex can be found without much searching.

Embryo of 53 mm. (fig. 12). Traces of the ultimobranchial bodies are present in the caudal half of the tripartite complex. The anterior end of each is represented by a small irregularly outlined vacuolar area which lies lateral to the median plane just below the dorsal surface of the gland. For some distance

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caudalward these areas become larger, in places very irregular in outline, in places broken up with typical thyroid structures, and are located more deeply in the lateral halves of the thyroid gland. The thyroid ends in a single blunt process that has a typically thyroid structure. In a few places the ultimobranchial bodies are unusually vacuolar. In these places the nuclei do not stain deeply (U). Similar lightly stained areas were observed by Kingsbury ('14) in the thyroid gland of human embryos. Also, a few groups or nests of small, closely packed nuclei were found. In some of these groups the nuclei had a normal structure, while in others they were only slightly stained. A few degenerated nuclei were found in the vacuolar areas and in their immediate neighorhood. Deeply stained nuclei are present in small numbers in both vacuolar and nonvacuolar parts.

Embryo of 60 mm. (fig. 13). The ultimobranchial bodies are limited to the posterior third of the thyroid gland. The right one is fused to the dorso-lateral margin of the gland and along its greater extent is composed of loosely arranged cell cords (U). Near the caudal end of the thyroid it merges into a vacuolar area which is interspersed with typical thyroid structures. The nuclei of the cell cords are on an average smaller than those found in the thyroid gland but, excepting a few darkly stained nuclei, they have a normal structure. The left ultimobranchial body lies just lateral to the median plane and is more deeply imbedded in the thyroid than the right one. It is largely composed of loosely arranged cell cords. Small vacuolar areas are present throughout its entire extent. The tripartite complex ends in a single process which is partly vacuolar. Mitoses can readily be found in the loosely arranged cell cords.

Embryos of 65 mm. The ultimobranchial bodies in two embryos of this developmental stage are described in order to contrast the structure of these bodies in two embryos of the same age. In one embryo these structures are represented by small disconnected vacuolar areas which are promiscuously scattered in the caudal half of the tripartite complex. In the other embryo the ultimobranchial bodies are located in the posterior third of the thyroid gland, and each one is characterized by a large and

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very irregularly outlined and continuous vacuolar mass to which coarse and loosely arranged cell cords, some of which are vacuolar, are attached. In the extreme caudal portion of the thyroid gland these structures fuse with each other and make up a large portion of its blunt termination. In each embryo a few deeply stained nuclei and a few degenerated nuclei were found.

Embryo of 75 mm. This is the youngest developmental stage in which colloid is found in the thyroid gland (picro-aceto-formol and hematoxylin and eosin). The follicles containing colloid are not numerous but are quite uniformly distributed throughout the anterior portion of the gland. The ultimobranchial bodies are limited to the posterior two-thirds of the gland lateral to the median plane and bordering the dorsal surface of the gland. They are represented by a continuous area of cell cords w^hich contains no colloid. Within these areas are found small, irregularly outlined, and disconnected syncytial masses which contain an unusually large number of small nuclei. These nuclei have the same structure as those found in the cell cords of the thyroid gland. Many of the cell cords which do not contain colloid are fused to these syncytial masses. Vacuoles are almost entirely lacking. A few^ degenerated nuclei are present, found only after prolonged searching. The tripartite complex ends in two blunt processes which have a typical thyroid structure.

Embryos of 100 mm. The tripartite complex of two embryos deserves notice. In both the colloid is more abundant than in the previous stage.

Embryo No. 1 (fig. 14). The ultimobranchial bodies are limited to the middle tw^o-fourths of the thyroid gland. The right one lies partially exposed on the dorsal surface of the thyroid lateral to its medial plane. In some places it is composed of coarse and loosely arranged cell cords (U), while in other parts the cell cords merge into a large syncytial mass. In places the connection between it and the thyroid is more intimate than is shown in figure 14. In the syncytial masses the nuclei are on an average a little smaller than those in the cell cords of the thyroid, but in both their structure is the same. No vacuoles are

106 J. A. BADERTSCHER

present. A few deeply stained nuclei are present. Some are also found in the cell cords of the thyroid gland. A few degenerated nuclei were found. The ultimobranchial body on the left side has a similar structure to the one on the right side but lies deeply buried below the dorsal surface of the gland. The portion of the tripartite complex which can be distinctly recognized as a derivative of the ultimobranchial bodies, and the cell cords in their immediate neighborhood contain no colloid although the cell cords have a typical thyroid structure of somewhat earlier stages.

Embryo No. 2. The ultimobranchial bodies cannot be identified structurally. However, it is to be noted that on the right side, lateral to the median plane and along the dorsal border in the middle third of the gland is an area which contains no colloid. This area is composed of closely packed cell cords which have the same structure as the cell cords of the thyroid just before the appearance of colloid, such as in a 60 mm. embryo. On the left is an area similar in structure to the one on the right side only its cephalo-caudal extent is considerably less. These areas which are free from colloid correspond favorably in position to that of the ultimobranchial bodies in some of the previous stages. The thyroid terminates in two rather blunt processes the extreme caudal portions of which contain no colloid.

Embryo of 111 mm. The ultimobranchial body on the right side of the gland is represented by two small and widely separated syncytial masses which extend through a series of ten and six sections respectively (10 microns in thickness), and on the left side it is represented by a syncytial mass extending through a series of eleven sections. These syncytial masses are quite vacuolar and the nuclei are comparatively small and clear and many are irregular in outline. Only a few darkly stained and degenerated nuclei are present.

It is of importance to note that on the right side lateral to the median plane in the middle two-fourths of the gland and in line with the syncytial masses described above is an irregularly outlined area of closely packed cell cords. This area is quite large in cross section and is free from colloid. A similar area of about the same length is present in the left side of the thyroid but it

FATE OF THE ULTIMOBRANCHIAL BODIES 107

extends farther caudally and not so far anteriorly as the right one. These areas which are free from colloid correspond favorably in position to that of the ultimobranchial bodies in some earlier developmental stages.

Embryos of 125 mm. The ultimobranchial bodies in two embryos of this developmental stage were examined.

Embryo No. 1 (fig. 15). The ultimobranchial body on the right side lies in the middle two-fourths of the thyroid gland. Its anterior end is deeply imbedded beneath the dorsal surface of the thyroid and is composed of a very irregularly outlined and vacuolar syncytial mass in which the nuclei have about the same size as those in the follicular epithelium of the thyroid. A few pale nuclei are present. Cell cords, some of which are coarse and vacuolar, lead from the vacuolar area and are fused with the surrounding thja-oid structures. Slightly farther caudal it reaches the free surface on the ventro-lateral side of the gland and is composed of a loose network of cell cords some of which are vacuolar. From this place it gradually occupies a more dorsal position in the thyroid gland and is composed of closely packed cell cords, having a structure similar to that of the thyroid gland just before the appearance of colloid. Its more caudal portion reaches the free surface of the thyroid gland on its dorsal aspect (U) and contains a large cyst (C).

The ultimobranchial body on the left side is represented by a. series of six small disconnected, and irregularly outlined syncytial masses which lie just lateral to the mesial plane of the gland. These areas are more or less vacuolar and do not contain any colloid. The thyroid ends in a single process throughout which the colloid is cjuite uniformly distributed.

Embryo No. 2 (figs. 16 a and 1Gb). The tripartite complex of this embryo is of interest in that the ultimobranchial bodies are only partially imbedded in the thyroid gland. The ultimobranchial body on the right side lies along the lateral margin of about the middle two-fourths of the thyroid gland to which it is fused. It is fusiform in shape, with its greatest diameter about midway between its ends (fig. 16 a, U). The free portion along its entire extent is composed of syncytial masses and coarse and tortuous cell cords in both of which are found cystoid follicles which are

108 J. A. BADERTSCHER

lined with cuboidal and columnar epithelium. Some of the nuclei in the syncytial masses and in the coarse cell cords stain more deeply than others, and in general they are more variable in size than those in the follicular epithelium of the thyroid gland. The nuclei in the epithelial lining of the cystoid folicles lie closely together and stain uniformly. While the cystoid follicles are free from colloid in this developmental stage, small follicles containing colloid are thinly scattered throughout its free portion (fig. 16 a, Co). Along the line of fusion of the free portion of the ultimobranchial body to the thyroid gland there is in the latter an area composed of cell cords in which colloid is just beginning to form (fig. 16 a). The cell cords of this area have a structure similar to those in earlier stages in which colloid formation has just begun. In the free portion of this structure vacuoles are almost entirely lacking and only a few degenerated nuclei were found.

The length of the ultimobranchial body on the left side is equal to the length of the right one. It also lies along the lateral margin of the thyroid gland but is more deepl}^ imbedded in it (fig. 16 b, U). In cross section it is smaller than the right one but, excepting the absence of cystoid follicles, it has a similar structure. By referring to the figure it will be seen that it merges gradually into the thyroid gland. The follicles containing colloid gradually become smaller toward the more central portion of the ultimobranchial body in which only an occasional small follicle can be found.

Embryo of 145 mm. (fig. 17). The ultimobranchial bodies on both sides are limited to the middle two-fourths of the thyroid gland just lateral to its median plane. The right one along nearly its entire extent is partly exposed to the free surface along the dorsal border of the gland. The portion most deeply imbedded in the thyroid gland is represented by an area of cell cords in which the follicles containing colloid are quite numerous but all very small (U). _ In places along its free margin are found cystoid follicles which also contain colloid {C.F.).^

' The substance in the cystoid follicles is called 'colloid' on the ground that it has a staining reaction identical to that of the colloid in the follicles of the thyroid gland.

FATE OF THE ULTIMOBRANCHIAL BODIES 109

The ultimobranchial body on the left side is exposed to the free surface only in a few places. The larger portion lies immediately beneath the dorsal border of the thyroid gland. In one of its exposed parts are found cystoid follicles which contain colloid. The imbedded parts have the same structure as the imbedded portion of the right one. No darkly stained nuclei were found in either of the ultimobranchial bodies.

Embryo of 150 mm. The ultimobranchial bodies are located in the middle and a part of the posterior third of the thyroid gland near its lateral borders. They are represented by areas of typical thyroid structures in which the follicles containing colloid are small and not very numerous. In places they reach the free surface of the gland along its lateral border. No cystoid follicles or deeply stained and degenerated nuclei are present.

Embryo of 160 mm. (fig. 18). The only structures present in the thyroid gland indicative of the presence of the ultimobranchial bodies are areas (C/), on each side lateral to the median plane along the dorsal surface of the gland. In these areas the follicles containing colloid are quite small in comparison to the large majority present in the thyroid gland, but appreciably larger than those found in corresponding areas in the thyroid of 145 and 150 mm. embryos. These areas extend from about the caudal end of the anterior third well into the posterior fourth of the thyroid gland which terminates in a rather blunt single process. In the caudal end are a very few large follicles containing colloid but it was impossible to determine whether or not they developed in connection with the ultimob ranchial bodies. No darkly stained or degenerated nuclei were found.

Embryo of 175 mm. The follicles in the thyroid gland are on an average considerably larger than those found in the preceding stage. They vary greatly in size but are uniformly distributed throughout the gland. No structures are present which can be interpreted as derivatives of the ultimobranchial bodies.

Embryo of 225 mm. (fig. 19). The only apparent traces of the ultimobranchial bodies are areas of considerable extent in which the follicles are comparatively small ([/). These areas are located in the middle third on each side of the median plane and

110 J. A. BADERTSCHER

along the dorsal surface of the thyroid gland, and compare in position to the ultimobranchial bodies in some other comparatively late developmental stages. The areas of small follicles on the right side is a little shorter than that on the left side.

Embryo of 245 mm. (fig. 20). On the right side along the lateral margin of the posterior two-thirds of the thyroid gland is an area containing many cystoid follicles which contain colloid and which are lined with cuboidal epithelium. This area, small anteriorly, gradually becomes larger and reaches its greatest cross-section area near the posterior fourth of the thyroid gland. From this position it decreases in size and near its termination it is almost separated from the thyroid gland. This area occupies a position similar to that of the ultimobranchial bodies in some earlier stages and apparently represents a partially imbedded ultimobranchial body similar to the right one in No. 2 of the 125 mm. embryo (fig. 16a).

On the left side lateral to the median plane and below the dorsal surface of the thyroid gland is an area in which the average size of the follicles is appreciably smaller than the large majority of follicles in other portions of the thyroid gland. This area lies in the posterior half of the thyroid gland but does not extend as far caudally as the area of large follicles on the right side. It also corresponds favorably in position to that most generally occupied by the ultimobranchial bodies in earlier stages.

Embryos of 270 mm. (full term). The thyroid glands of two full term embryos were examined.

Embryo No. 1. The follicles containing colloid are variable in size but uniformly distributed throughout the gland. The only portion of the gland which can be interpreted as a derivative of an ultimobranchial body is an area of only small follicles on the right side lateral to the median line in the posterior half of the gland. This area extends through a series of only sixty sections (10 microns in thickness) and lies hear the dorsal surface of the gland.

Embryo No. 2 (fig. 21). The thyroid gland extends through a series of 827 sections (10 micrxjns in thickness). The left ulti

FATE OF THE ULTIMOBRANCHIAL BODIES 111

mobranchial body is not completely transformed into typical thyroid structures. It lies in the posterior half of the gland and can be traced through a series of 234 sections (2.3 mm.). It is characterized by a small area of tortuous and nonvacuolar syncytial cords free from colloid which is eccentrically located in an area of small follicles (U). The nuclei in the syncytial cords correspond in size and structure to those in the follicular epithelium. A few nuclei in mitotic division are present. No deeply stained or degenerated nuclei are present.

The right ultimobranchial body extends through a series of 243 sections and is found in the middle third of the thyroid gland. It is characterized by an area of small follicles. In both ultimobranchial bodies from their more central portion toward their periphery the follicles gradually become larger. There is no sharp line of demarcation between these structures and the thyroid gland.

V. SUMMARY AND DISCUSSION

By comparing the rate of growth of the ultimobranchial bodies and the thyroid gland, it is seen that a more uniform size ratio is maintained in early than in later developmental stages. During this 'periode d'activite' (Simon) of the ultimobranchial bodies, which extends from an 18 mm. or earlier developmental stage to about a 33 mm. stage, the cephalo-caudal extent of the ultimobranchial bodies is nearly or entirely equal to that of the thyroid gland. In later stages (33 mm. to full term) in which the ultimobranchial bodies can be recognized structurally, their cephalocaudal extent is generally much less . than that of the thyroid gland, which indicates that in later developmental stages the rate of growth of the thyroid exceeds that of the ultimobranchial bodies. In embryos from about 50 mm. in length to full term the ultimobranchial bodies are usually located in the posterior half of the thyroid gland. In a few stages they occur in the middle third or the middle two-fourths of the gland. Simon ('96) claims that during this period of retarded growth of the ultimobranchial bodies, which he calls the 'periode de survivance,' they undergo degenerative changes which is manifested prin

112 J. A. BADERTSCHEU

cipally by cystic formations (guinea-pig, rabbit, cat, calf, sheep) or their complete disappearance (pig) .

The ultimobranchial bodies first fuse with the thyroid gland along their ventro-lateral border. In early stages (19 mm. to about 27 mm.) they make up a considerable portion of the horns of the crescent-shaped tripartite complex. The extent of their fusion to the thyroid gland during their period of retarded growth (from about 33 mm. to full term) is variable. In the majority of late stages they are entirely imbedded in the thyroid gland while in some they are only partially imbedded. The latter condition is particularly the case in the following embryos; 48 mm. (figs. 11 a and 11 b); 60 mm. (fig. 13) ; 100 mm. (fig. 14); 125 mm. (fig, 16 a and 16 b); and 145 mm. (fig. 17). In the later stages they usually lie more or less deeply imbedded below the dorsal surface of the thyroid gland lateral to its medial plane, but occur less frequently along the lateral or dorso-lateral margin of the gland.

The formation of vacuoles in the ultimobranchial bodies begins before their fusion with the thyroid gland has occurred and continues after fusion. However, in the various stages examined no ultimobranchial body was found that is vacuolar throughout. In human embryos Kingsbury ('14) finds that vacuolation, 'reticulation,' continues until the entire structure is altered in this way. The extent to which vacuolation takes place varies in embryos of the same and different developmental stages. For example in No. 1 of the 125 mm. embryos the more central portion of these structures are quite vacuolar while in No. 2 of the 125 mm. embryos no vacuoles are present. Also no vacuoles are present in the left ultimobranchial body in No. 2 of the 27G mm. embryos. In early stages non-vacuolar portions are present along the periphery as well as in the deeper portions of these structures. In later stages in which the ultimobranchial bodies are largely broken up into cell cords the vacuoles are most numerous in their more central unbroken portion although vacuolated syncytial cords were found. In a few stages of which the embryo 53 mm. long is an example, the only part of the ultimobranchial body that can be recognized structurally as such are

FATE OF THE ULTIMOBRANCHIAL BODIES 113

small vacuolar syncytial masses entirely surrounded by typical thyroid structures (fig. 12).

Up to about a 24 mm. stage a marked contrast exists in the structure of the ultimobranchial body and the thyroid gland, in that the former are largely unbroken syncytial masses, \\'hile the latter is broken up into cell cords (as seen in cross section) . Although epithelial buds produce irregularities on the surface of the ultimobranchial bodies even in a 21 mm. stage and indications of cell cord formation were found in one 22 mm. embryo, the process of extensive cell-cord formation in these structures is particularly active in stages ranging from 24 to 27 mm. in length. The larger caudal end becomes broken up somewhat later than the smaller anterior end. Usually, also, the more central portion breaks up into cell cords later than the periphery. The syncytial cords when first formed are usually larger or coarser than those of the thyroid gland. Many are vacuolar for some distance away from the central more or less vacuolar core to which they may be attached. The time of breaking up of the central core into cell cords is very variable. The extent to which the ultimobranchial bodies become invaded with vascular tissue corresponds closely to the extent of cell cord formation. The first blood vessels, which are of a capillary nature, are found in these structures in a 23 mm. embryo.

According to Simon ('96) the cell cores of the ultimobranchial bodies are formed in an entirely passive way, namely, by the ingrowth of vascular tissue and of structural elements of the median thyroid. That the former is a potent factor in this process is, I believe, beyond doubt. It appears to me, however, that he lays too much stress on the formation of cell cords by the ingrowth of thyroid structures which will be considered later. Another active factor in the process of cell cord formation is a continued growth and branching of the epithelial buds found on their surface in early stages. The buds by continued growth and branching take the form of coarse cell-cords which can in many instances be recognized structurally from the smaller cell cords of the thyroid gland by the larger proportion of small nuclei which they contain and by vacuoles which, when present, are

114 J. A. BADERTSCHER

found in their more proximal ends near their attachment to the more central unbroken portion of these bodies. Also, in stages in which the darkly stained nuclei are numerous many can usually be found in the coarse cell cords. The presence of nuclei in mitotic "division in these cords is further evidence that they really grow.

The cell cords of the ultimobranchial bodies when first formed are generally more loosely arranged than those of the thyroid gland (figs. 9, 10 c, and 13). The time at which they become more compactly arranged and resemble in appearance the thyroid gland previous to the appearance of colloid in the latter, varies greatly. For example, in embryos of 48 and 53 mm. in length, excepting the small vacuolar portions, they have a structure, similar to the thyroid gland, while in both 125 mm. embryos cell cords in portions of these structures have still a quite loose arrangement.

The deeply stained nuclei are most numerous in the ultimobranchial bodies in stages from 20 mm. to about 30 mm. in length. In the first half of this brief developmental period (20 to 30 mm.) the ultimobranchial bodies attain their largest size as unbroken or solid structures while in the latter half of this period the process of cell cord formation is very active. The deeply stained nuclei diminish in number in stages beyond 30 mm. in length and finally disappear altogether. Their decrease in number is, however, not uniform in successively older stages. For example, in a 35 mm. embryo in which the only structural traces left of the ultimobranchial bodies are small disconnected vacuolar areas, the darkly stained nuclei are comparatively few in number, while in a 37.5 mm. embryo in which these structures are still large and easily traceable, the darkly stained nuclei are quite numerous. In late developmental stages in which the ultimobranchial bodes can be structurally recognized as such the darkly stained nuclei have largely or entirely disappeared. For example in No. 2 of the 125 mm. embryos there are some present although not in large numbers, while in the ultimobranchial bodies in No. 2 of the full term embryos no darkly stained nuclei are present.

FATE OF THE ULTIMOBRANCHIAL BODIES 115

The deeply stained nuclei have been regarded by Simon ('96) as degenerating nuclei. In only two developmental stages (23 and 24 mm. embryos, fig. 7) were degenerated nuclei found in sufficient number to suggest a general degeneration of these structures. In some of the later developmental stages degenerated nuclei were also found but always in small numbers. It appears that the degenerated nuclei are derived from the darkly stained nuclei although I was unable to trace their source through intermediate forms directly to them. Some of the nuclei in connective tissue cells, in developing muscle fibers, in epithelial cells lining the esophagus, and also in some stages in the cell cords of the thyroid gland, stain deeply. This gives them a structural appearance quite similar to those found in the ultimobranchial bodies. The presence of these nuclei in various developmental structures suggested the probability that the dark nuclei in the ultimobranchial bodies are in a certain physiological state. This, however, is mere conjecture. If they represented a general degeneration of the ultimobranchial bodies one would naturally expect to find large numbers of degenerated nuclei in later developmental stages, but a contrary condition is the case. They gradually decrease in number while the ultimobranchial bodies continue in their growth. This fact seems to me to be strong evidence in favor of the persistence of these structures.

A feature quite noticeable in the ultimobranchial bodies in most of the earlier developmental stages and in some of the quite late stages is the small and variable size of some of the ultimobranchial nuclei. Grosser ('10) and Kingsbury ('14) also observed small ultimobranchial nuclei in human embryos. The small nuclei are very variable in number in stages of about the same age. Some of these nuclei also stain deeply in stages in which deeply stained nuclei are present, and in a few instances groups of pale small nuclei were found. However, the large majority of the small ultimobranchial nuclei have a normal structure, in all stages in which they occur. In late stages no small nuclei are present. Although the significance of the darkly stained and the small ultimobranchial nuclei are unknown to me I am

116 J. A. BADERTSCHER

convinced that they do not represent a general degeneration ot the iiltiniobranchial bodies.

Follicles containing colloid appear first in the thyroid gland in a 75 mm. embryo. In the ultimobranchial bodies the follicles containing colloid are first quite numerous, though small (excepting the cystoid follicles), in a 145 mm. embryo (fig. 19). A few small follicles containing colloid were found in these structures in the 125 mm. embryos. The retarded development of colloid in the ultimobranchial bodies in the pig corresponds with a similar retardation in its development in these structures in the Echidna in which, according to Maurer ('99), they remain independent structures. The time at which the transformation of the ultimobranchial bodies into typical thyroid structures is completed, that is, when they can no longer be distinguished from the derivatives of the median thyroid anlage, is variable. For example in a 175 mm. embryo their transformation is complete while in No. 2 of the full term embryos the left one is composed of an area of small follicles in which is located a small area of cell cords free from colloid (fig. 21). A comparison of the structure of the right ultimobranchial body, which is composed of an area of small follicles, and the left one in No. 2 of the full term embryos also shows that one ultimobranchial body may undergo a more rapid transformation into typical thyroid structures than the other in the same embryo.

Cell cords are formed from the periphery of the ultimobranchial bodies usually sooner than from their more central portion, as stated above. It is also in the cell cords of the peripheral portion of the ultimobranchial bodies that colloid is first formed, so that the older peripheral follicles of these structures in many stages are larger than the more centrally located ones. Figures 18, 19, and 21 show that the follicles containing colloid gradually decrease in size toward the more central portions of these structures. Since colloid appears first in the thyroid gland many of the follicles are quite large before colloid is first formed in the ultimobranchial bodies. It would thus seem that if the ingrowth of structural elements of the thyroid gland into the ultimobranchial bodies is a factor in breaking up the latter into cell cords,

FATE OF THE ULTIMOBRANCHIAL BODIES 117

as claimed by Simon, there would be some quite large thyroid follicles found in the deeper portion of the ultimobranchial bodies among the smaller ultimobranchial follicles which begin to develop comparatively late. However, excepting the cystoid follicles in the ultimobranchial bodies in some of the later stages, this condition is not found. The follicles containing colloid gradually increase in size from the more central portion to the periphery of these structures. It therefore seems that the contention of k^imon is incorrect.

It also appears that in a few stages by far the larger portion of the ultimobranchial bodies undergo a transformation into typical thyroid structures even before colloid is formed in the thyroid gland. For example in embryos of 35 and 53 mm. in length the only structural features of the tripartite complex that can be interpreted as derivatives of the ultimobranchial bodies are small vacuolar areas (fig. 12) in contrast with the loosely arranged cell cords of these structures as found in embryos 37.5 and 60 mm. in length. Since in early stages it is impossible to distinguish the minute structure of the nonvacuolar portions of an ultimobranchial body from that of the thyroid gland when both are seen in the same microscopic field under high magnification, I believe that the vacuolar areas in embryos of 35 and 53 mm. in length represent only the more central cores of ultimobranchial bodies of which their more peripheral portion has undergone an early transformation into typical thyroid structures. This interpretation is supported by the conditions presented in a 48 mm. embryo in which the anterior portion of each ultimobranchial body is isolated from the thyroid gland. Excepting a small vacuolar area and traces of a lumen found in the isolated portion of the left one, the isolated portion of each of these bodies has a structure similar to the thyroid gland along which it lies.

I am of the opinion that the so variable developmental behavior of the ultimobranchial bodies in pig embryos throws light on a disputed point in connection with the development of these structures in human embryos. Grosser ('10) writes of a 'dichtere Zellgruppierung' in the thyroid gland of a human embryo

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118 J. A. BADERTSCHER

50 mm. long. He however does not believe that this dense cell area is derived from an ultimobranchial body but that it is ■'niir der Ausdruck intensivem Wachstums der ganzen anlage, wiihrend die Differenzierung der neugebildeten Strange mehr oberflachlich stattfindet; die Zellen sind durchwegs typische Thyreoideazellen." Kingsbury ('14) finds that a human embryo 25 mm. long is the last stage in which the ultimobranchial body is clearly outlined. Their position in succeeding stages up to 41 mm. is occupied by a poorly circumscribed area of denser tissue." He is of the opinion that this "inner condensation" marks the place of disappearance of the ultimobranchial body although it may also well be as Grosser has stated, a center of growth." He further states that in 41 mm. and later developmental stages the "condensation is no longer recognizable." Although he was unable to satisfy himself as to the actual fate of the ultimobranchial bodies, he is of the opinion that they disappear.

From a study of the material used in this investigation I feel confident that the structure described by Grosser represents an ultimobranchial body. The process of cell cord formation at the periphery of the 'dichtere Zellgruppierung,' as described by him, corresponds favorably to the process of their formation in the ultimobranchial l3odies in pig embryos. Both the 'inner condensation' (Kingsbury) and the 'dichtere Zellgruppierung' (Grosser) apparently represent the central core which in the ultimobranchial bodies of pig embryos is found in a very wide range of developmental stages, even in a full term embryo (fig. 21). It seems that if the 'dichtere Zellgruppierung' represented a proliferati\'e center for the thyroid gland one would expect to find a rather large number of mitotic figures in them as an expression of rapid tissue growth. This, however, is not the case. No more nuclei in division are found in these areas than in any other portion of the thyroid gland.

The stages in which a comparatively early transformation of the greater portion of the ultimobranchial bodies takes place are comparatively few in ninnl)er. Also there are comparati\'ely few stages before full term in which there are no areas of small follicles

FATE OF THE ULTIMOBRANCHIAL BODIES 119

(ultimobranchial bodies) present. Judging, therefore, from the so variable developmental behavior of the ultimobranchial bodies it seems that the 175 mm. stage referred to above is one in which the ultimobranchial bodies underwent an early transformation into typical thyroid structures.

The portion of the structural elements of the thyroid gland at birth derived from the ultimobranchial bodies is small in comparison to the part derived from the median thyroid anlage. Owing to the variable de\'elopmental behavior of the former structures the comparative proportion contributed by them and the median thyroid anlage undoubtedly varies in different embryos. Figures 22 a, 22 b, and 22 c are diagrammatic representations of the portions derived from the median thyroid anlage and the ultimobranchial bodies in No. 2 of the 270 mm. (full term) embryos.

In the posterior portion of the right ultimobranchial body in No. 1 of the 125 mm. embryos is a cyst which extends through a series of sixty-seven sections (10 microns in thickness). It is lined with cuboidal epithelium the cytoplasm of which stained only very faintly. In one place in its lumen an isolated group of cells is found. The nature of its formation is unknown to me. According to Simon ('96) the formation of cysts in these structures is a regular occurrence during their 'periode de survivance' in all animals examined by him, excepting in the pig in which they occurred in five out of eleven specimens. Since cyst formation occurred in only one specimen out of those I studied, it seems to be an exceptional developmental feature in the pig.

VI. CONCLUSIONS

1. The ultimobranchial bodies in the pig participate in the formation of thyroid follicles. However, the portion of the gland in full term embryos that is derived from these structures is small in comparison with the part derived from the median thyroid anlage.

2. The cephalo-caudal extent of the ultimobranchial bodies is equal to or nearly equal to that of the thyroid gland in embryos up to about 33 mm. in length. From this stage on to full term

120 J. A. BADERTSCHER

the latter grows more rapidly in size than the former so that in stages from about 50 mm. in length to full term the ultimobranchial bodies usually lie in the posterior half of the thyroid gland but may be found in the middle third or in the middle two-fourths of the gland.

3. The developmental stages in which the ultimobranchial bodies transform into typical thyroid structures (that is, when they can no longer be recognized structurally from the median thyroid anlage) , vary greatly. The transformation of the greater part of these structures may take place as early as in a 35 mm. stage, before colloid is present in the thyroid gland, but in the majority of stages examined it takes place in later stages. Even in full term embryos an entire ultimobranchial body may not be completely transformed.

4. The ultimobranchial bodies in a thyroid gland may vary in size, in shape, in the degree of their transformation, and in their location in the lateral halves of the thyroid gland. This variability is particularly pronounced in some of the later developmental stages.

5. Colloid first appears in the follicles of the thyroid gland in embryos of 75 mm. in length. A few small follicles containing colloid appeared first in the ultimobranchial bodies of a 125 mm. embryo. In a 145 mm. embryo the follicles containing colloid in these structures are quite numerous although on an a\'erage small in comparison with those in the thyroid gland.

6. Large cystoid follicles containing colloid may develop in the ultimobranchial bodies.

7. The ultimobranchial bodies usually become entirely imbedded in the thyroid gland. In a few developmental stages they were found to be only partially imbedded.

8. The formation of cysts in the ultimobranchial bodies of pig embryos is of rare occurrence.

FATE OF THE ULTIMOBRANCHIAL BODIES 121

VIII. BIBLIOGRAPHY

Born, G. 1883 Uebcr die Derivate dcr embryonalen Schlundbogen und Schlund spalten bei Sjiugctieren. Arch. f. mikr. Anat., Bd. 22. FiscHELis, P. 1885 Beitriige zur Kenntniss der Entwickelungsgeschichte der

Gl. Thyreoidea und Gl. Thymus. Arch. f. mikr. Anat., Bd. 25. Fox, H. 1908 The pharyngeal pouches and their derivatives in the mammalia,

Am. Jour. Anat., vol. 8. Getzowa, S. 1907 Ueber die glandula parathyreoidea, intrathyreoidale Zell haufen derselben und Reste des postbranchialen Korpers, Arch. f.

path. Anat., Bd. 188. Greil, a. 1905 Ueber die Aniage der Lungen, sowie der ultimobranchialen,

(postbranchialen, suprapericardialen) Korper bei anuren Amphibien,

Anat. Hefte, Bd. 29. Grosser, O. 1910 Zur Kenutnis des ultimobranchialen Korpers beim Mem chen, Anat. Anz., Bd. 37.

1912 The development of the pharynx and of the organs of respiration.

Manual of Human Embryology, edited by F. Keibel and F. P. Mall,

vol. 2. Herrmann, G. and Verdun 1899 Persistance des corps post-branchiaux chez

I'homme. Remarques sur I'anatomie comparce des corps post-branchiaux. Comptes Rend. Soc. Biol. Paris.

1900 Note sur les corps post-branchiaux des Cameliens. Les corps

post-branchiaux et la thyroide; vestiges kystiques. Comptes. Rend.

Soc. Biol. Paris. Kast.schenko, N. 1887 Das Schicksal der embryonalen Schlundspalten bei

Saugetieren. Arch. f. mikr. Anat., Bd. 30. Kingsbury, B. F. 1914 On the so-called ultimobranchial body of the mammalian embryo: Man. Anat. Anz., Bd. 47. KoHN, A. 1897 Studien liber die Schilddriise, II. Arch. f. Mikr. Anat., Bd. 38. Maurer, F. 1899 a Die Schilddriise, thymus und andere Schlundspaltenderi vate bei der Eidechse. Morph. Jahrb., Bd. 27.

1899 b Die Schlundspalten-Derivate von Echidna. Anat. Anz.

Ergjinzungsheft, Bd. 16. Moody, R. M. 1912 Some features of the histogenesis of the thyroid gland in

the pig. Reprints of Papers from the Dept. of Anat. of the Univ. of

Cal., vol. 4. NoRRis, E. H. 1910 The morphogenesis of the follicles in the human thyroid

gland. Am. Jour. Anat., vol. 20. Prexant, a. 1894 Contribution a I'etude organique et histologique du thymus,

de la glande thja-oide et de la glande carotidienne. La Cellule, T. 10. Rabl, H. 1913 Die Entwicklung der Derivate des Kiemendarms beim Meer schweinchen. Arch. f. mikr. Anat., Bd. 82. Schapfer, J., AND Rabl, H. 1908 and 1909 Das thyreothymische System des

Maulwurfs und der Spitsmaus. I. Morphologic und Histologic by J.

Schaffer. II. Die Entwicklung des thyreothymischen System beim

Maulwurf by H. Rabl. Sitzber. kais. Akad. Wiss. Wien, vols. 117

and 118.

122 J. A. BADERTSCHER

Simon, Ch. 1896 'I'hyroide later;ilc et glandule thyroidienne chez les mam miferes, These de Xancy. Symington, J. 1897 t ber Tliyreoidea, Glandylae parathyreoidcae und Thymus beim dreizehigen Faulthier (Ai, Bradypus tridactylus). Arch. f.

Anat. u. Physiol. Supplement-Band zur Anat. Abt. TouRNEUX, F., and Verdun, P. 1897 Sur les premiers developpements de la

thyroide, du thymus et des glandules thyroidiennes Chez L'Homme.

Journ. de Anat. et de la Phys., T. 23. Verdun, P. 1898 Contribution a I'etude des derives Branchiaux chez les ver tcbres superieurs, These, Toulouse. ZucKERKANDL, E. 1903 Die EntM icklung dcr Schilddruse und der thymus bei

der Ratte. Anat. Hefte, Bd. 21.

PLATES

123

PLATE 1

EXPLANATION OF FIGURES

1 From a photogi'aph of a transverse section of the ultimobranchial bodies and the thyroid gland about midway between the anterior and posterior ends of the latter. Before the fusion of the ultimobranchial bodies with the thyroid gland. From an embryo 18 mm. long. X 60.

2 a and 2 b From photographs of transverse sections of the ultimobranchial bodies and the thyroid gland taken respectively near the anterior and posterior ends of the latter. P'usion between the ultimobranchial bodies and the thyroid gland has in some places taken place. From an embryo 19.5 mm. long. X 60.

3 a, 3 b, and 3 c From photographs of transverse sections of the ultimobranchial bodies and the thyroid gland taken respectively near the anterior, middle, and posterior portions of the latter. The numerous deeply stained nuclei in the ultimobranchial bodies are represented by small black dots. From an embryo 20 mm. long. X 60.

4 From a photograph of a transverse section about midway between the two ends of the tripartite complex. The horns of the crescent are largely composed of the ultimobranchial bodies the left one of which is quite irregular along its dorso-mesial surface due to epithelial buds. From an embryo 21 mm. long, X 60.

5 From a photograph of a transverse section about mid.vay between the two ends of the tripartite complex showing the large size of the ultimobranchial bodies. From an embryo 21.5 mm. long. X 60.

6 a and 6 b From photographs of transverse sections through near the middle and caudal portions respectively of the tripartite complex, showing nvunerous deeply stained nuclei (small black dots in the figures) in the ultimobranchial bodies and a few in the cell cords of the thyroid gland. The figures also show that the caudal portion of the ultimobranchial bodies are less broken up into cell cords than their more anterior portion. From an embryo 22 mm. long. X 60.

7 From a photograph of a portion of an ultimobranchial body showing degenerated and deeply stained nuclei. From an embryo 23 mm. long. X 650.

D.N., degenerated nuclei T., thyroid gland

D.S.N. , deeply stained nuclei Tr., trachea

Ep. B., epithelial buds U., ultimobranchial body L., lumen

124

FATE OF THE ULTI.MOHKAXCHIAI. BODIES

J. A. BADERTSCHEU

PLATE 1

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6 a

125

PLATE 2

EXPLANATION OP FIGURES

8 a, 8 b, and 8 c From photographs of transverse sections through near the anterior, middle, and posterior portions respectively of the tripartite complex, showing the gradual enlargement of the ultimobranchial bodies from their anterior to their posterior ends. The posterior end of the tripartite complex is largely composed of the ultimobranchial bodies. From an embryo 23 mm. long. X 60.

9 From a photograph of a transverse section about midway between the two ends of the tripartite complex showing the ultimobranchial bodies largely broken up into coarse cell cords. From an embryo 27 mm. long. X 56.

10 a, 10 b, and 10 c From photographs of transverse sections through the anterior, middle and posterior portions respectively of the tripartite complex. The ultimobranchial body on the left side extends along the posterior threefourths of the thyroid gland while the right one along only its posterior fourth. The unecjual size of the two ultimobranchial bodies, which are largely broken up into coarse cell cords, produce the asymmetry of the tripartite complex. From an embryo 29.5 mm. long. X 56.

11 a and 11 b From photographs of sections through the anterior and nearly the middle portions respectively of the tripartite complex showing both ultimobranchial bodies separated from the anterior portion of the thyroid gland (fig. 11 a) and the left one with traces of the lumen also separated from the thyroid (fig. 11 b). From an embryo 48 mm. long. X 60.

Ep.B., epithelial buds Tr., trachea

L., lumen U., ultimobranchial body

T., thyroid gland

126

FATE OF THE ULTIMOBRANCHIAL BODIES

J. A. BADEHTSCHEU

PLATE 2

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127

PLATE 3

EXPLANATION OF FIGURES

12 From a photograph of a small portion of a section through an ultimobranchial ])ody (the light area in the figure) which merges gradually into typical thyroid structures. In the light area the majority of the ultimobranchial nuclei do not stain deeply. From an embryo 53 mm. long. X 337.

13 From a photograph of a portion of a transverse section of the tripartite complex showing the right ultimobranchial body which is largely composed of coarse and loosely arranged cell cords. From an embryo 60 mm. long. X 60.

14 From a photograph of a portion of a section of the tripartite complex showing the right ultimobranchial body which, in this particular place, is composed of loosely arranged cell cords in which no colloid is present. From an embryo 100 mm. long. X 56.

15 From a photograph of a portion of a transverse section through the posterior portion of the tripartite complex showing the compactly arranged cell cords of the right ultimobranchial body in which is located a cyst. The area inside the dotted circle is free from colloid. From an embryo 125 mm. long. X 45.

16 a and 16 b From photographs of portions of a transverse section of ths tripartite complex showing respectively the right and left ultimobranchial bodies. The right one is only partially imbedded in the thyroid gland and contains many cystoid follicles (C.i^.)'which do not contain colloid and a few small follicles which contain colloid (Co). The black dots in the portion of the figure labeled 'thyroid' represent colloid. The left ultimobranchial body is more deeply imbedded in the thj-roid gland. From an embryo 125 mm. long. X 38.

17 From a photograph of a portion of a transverse section of the trip:.rtite complex showing the right ultimobranchial body in which are found both small and cystoid follicles that contain colloid. From an embryo 145 mm. long. X 38.

18 From a photograph of a portion of a section of the tripartite complex showing the left ultimobranchial body which is represented by an area of small follicles. The black dots in the figure represent colloid. From an embryo 160 nun. long. X 38.

C, cyst T., thyroid gland

C.T., cystoid follicles U., ultimobranchial body

Co., colloid

128

FATE or THE ULTIMOBRANCHIAL BODIES

J. A. IlAnEHTSCHF.R

PLATE 3

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129

PLATE 4

EXPLANATION OF FIGURES

19 From a photograph of a portion of a section through the left ultimobranchial body and a portion of the thyroid gh\nd surrounding it. The ultimobranchial body is characterized by follicles which contain colloid and which are on an average appreciably smaller than the follicles of the thyroid gland. From an embryo 225 mm. long. X 38.

20 From a photograph of a portion of a section through the right ultimobranchial body and a portion of the thyroid gland surrounding it. The ultimobranchial body contains many cystoid follicles which contain colloid. The colloid dropped out from some of the follicles during the process of staining. From an embryo 245 mm. long. X 38.

21 From a photograph of a portion of a section through the left ultimobranchial body and a portion of the thyroid gland. The ultimobranchial body is characterized by an area of small follicles in which is located a small area free from colloid. The light dots represent follicles from which the colloid has fallen. This figure represents the ultimobranchial body at C in figure 22 a. From No. 2 of the embryos 270 mm. long (full term). X 38.

22 a, 22 b, and 22 c These figures show the relative size of the ultimobranchial bodies and the thyroid gland in No. 2 of the embryos 270 mm. long (full term). The extent of the ultimobranchial bodies is outlined by a dotted line. Inside the left ultimoljranchial body is a small area (X), also outlined by a dotted line, which is free from colloid (figs. 22 a and 22 c). The portion of the left ultimobranchial body outside the area X and all of the right one is characterized by follicles which are on an average appreciably smaller than those of the thyroid gland. Figures 22 b and 22 c represent cross sections through the tripartite complex at b and c respectively of the structures represented in figure 22 a. X 7.5.

T., thyroid U., ultimobranchial body

130

FATE OF THE ULTIMOBRANCHIAL BODIES

J. A. BADERTSCHER

PLATE 4

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131

ATTHOR S ABSTRACT OF THIS PAPER ISSUED BY THE BIBMOGRAPHIC SERVICE, DECEMBER 1

CHONDRIOSOMES IN THE TESTICLE-CELLS OF FUNDULUS

J. DUESBERG

Carnegie Institution, Department of Embryology, Baltimore, Maryland

TWENTY-ONE FIGURES (tWO PLATES)

Our knowledge of chondriosomes in the spermatogenesis of fishes is limited, as far as I know, to an incomplete account on Myx3^noids by A. and K. E. Schreiner ('05, '08). In the ripe spermatozoon, however, the same bodies have been studied, especially by Retzius, in quite a large number of species.

According to A. and K. E. Schreiner, the chondriosomes are represented in the spermatogonia as well as in the spermatocytes of Myxine glutinosa by very small granules, tightly crowded together in the neighborhood of the 'Sphare.' No change in shape is observed during mitosis ; furthermore, the behavior of the mass of mitochondria seems to be entirely passive and consequently its segregation between the daughter-cells is often unequal. Concerning the process of spermiogenesis, these authors mereh^ state that the mitochondria build a sheath around the axile filament. It must be added that the preservation of the chondriosomes in the material used by A. and K. E. Schreiner can hardly be considered as satisfactory. ♦

Retzius has studied the ripe spermatozoon of Amphioxus ('05 b), of several selachians ('09 c; '10 b), of one ganoid (Amia calva, '05 b) and of a number of teleosts ('05 b; '10 b). As data concerning the process of spermiogenesis in selachians are lacking, in reference to the chondriosomes at least, it is hardly possible to decide what part of the spermatozoon is formed by these bodies. In the other classes however, their identification is easier and the concordant observations of Retzius on Amphioxus, Amia and teleosts can be summarized as follows : the chondriosomes of the ripe spermatozoon are located at the posterior part of the head

133

THE AMERICAX JOURNAL OF ANATOMY, VOL. 2.3, NO. 1

134 J. DUESBEKG

and surround usually for a short distance the proximal part of the tail. The shape of this sheath varies with the different species. In Amphioxus the chondriosomes are represented by a rather voluminous body in which, by careful study, one can make out three to five granules. In Amia, such a body appears indistinctly granular and fits the posterior part of the head as the cup fits the acorn. In teleosts similar dispositions are found, for the details of which I refer to Retzius' papers. I wish to emphasize that in a number of species the granules are very distinct and even constant in number. In Lophius piscatorius for instance, Retzius ('10 b) invariably found four of them, disposed in regular order around the origin of the tail.

It may well be recalled that a similar disposition of the chondriosomes has been observed in invertebrates. For instance, according to the observations of Meves ('00, '03), each spermatid of the apyrene generation of Paludina vivipara contains four chondriosomes. They assume the form of spheres and occupy the posterior part of the head, where they surround the axile filament. Bonnevie ('07) gives a similar description for Membranipora pilosa. In these cases however, this stage is a transitory one, for the shape of the chondriosomes changes during the further evolution of the spermatid, while in other invertebrates the same arrangement is, according to Retzius, retained in the ripe spermatozoon, namely, i-n a number of celenterates ('04 a and b; '05 a; '09 a), in many echinoderms ('04 a and b; '05 a; '10 a), ^ in worms ('04 a and b; '05 a; '06 b, c and d; '09 b) and in moMuscs ('04 a and b; '05 b; '06 a; '10 b). In many species belonging to the two last-named classes the numerical constancy of the chondriosomal spheres and the regularity of their arrangement around the axile filament are conspicuous features of the ripe spermatozoon. Especially remarkable is the disposition in

1 Meves ('12) contests the accuracy of Retzius' description for Parechinus miliaris. He finds that the so-called 'Mittelstiick' is not granular, as stated by Retzius, but homogeneous, and that it has the shape of a ring, through which runs the axile filament. I take this opportunity to remind how inadequate is the expression 'Mittelstiick' or 'middlepiece,' as, between the 'Mittelstiick' of the spermatozoon of an echinoderm, of a selachian or a urodele amphibian and of a mammal, there is no homology whatever.

TESTICLE-CELLS OF FUNDULUS 135

polychetes: the granules in many species are consistently four in number, their form being exactly spherical, their volume equal and their disposition around the proximal part of the tail perfectly regular.

The origin of these bodies is briefly referred to by Retzius ('04 a and b) who states (for molluscs) that the large spheres are formed by the confluence of smaller granules. Previously, Pictet ('91) and Field ('95) both had described the formation of the so-called 'mittelstiick' in the spermatozoon of echinoderms through fusion of highly refractive granules which, however, they erroneously derived from remnants of the spindle.

Quite recently M. R. Lewis ('17) has stained the chondriosomes (the so-called 'middlepiece') of the spermatozoon of Cerebratulus lacteus and of Echinorachnius parma in vivo, by using a solution of Janus-green in sea-w^ater. The object of the present investigation is the testicle of Fundulus (heteroclitus and majalis), the main purpose being to study the behavior of the chondriosomes during spermatogenesis. The material was collected in Woods Hole, Mass., in June, 1916, and fixed in Regaud's or in Benda's fluid, the latter either with or without acetic acid. The sections, 5 n thick, were stained in the first case with iron-haematoxyhn or acid f uchsin-methylgreen ; after Benda's fixation, I resorted to iron-haematoxylin acid, fuchsin-methylgreen or Benda's stain, the lattef giving, as previously stated for embryos ('17), a very small percentage of good preparations. A number of sections were stained with safranin, hi order to study the chromatin.

Once more I found that the preservation of the tissue is much better after Benda's fixatian than after Regaud's. This last reagent has a pronounced tendency to make the seminal cells

2 In the same paper, M. R. Lewis (p. 33) quotes my opinion, as expressed in my review ('12j, on the vital staining of chondriosomes and, from this quotation, one might be induced to conclude that, for me, neutral red and methylenblue can be used or have been used to stain the chondriosomes in vivo. To prevent any misunderstanding, I wish to recall that this has never been my opinion, as appears clearly in the quoted place of my article (p. 608), as well as in several others (for example, page 823, in the discussion of Arnold's plasmosomes).

136 J. DUESBERG

swell. The extent to which the ground substance is affected is well illustrated by the difference in size exhibited by the cells represented in figures 10 and 11, both in exactly the same stage of evolution, the first from material fixed in Benda's fluid, the second from material treated with Regaud's. Thus, cells which normally float freely in the cystic cavity are made to conglomerate and stick together. The chondriosomes are also sw^ollen, and the chromosomes are transformed into an undecipherable clump. In contrast to this, the last-named bodies are well preserved in Benda's material, an appearance which confirms that swelling in Regaud's rather than shrinking in Benda's fluid is responsible for the differences between the two sets of preparations.

The testicle of Fundulus is at the time of spawning a rather voluminous organ formed by a considerable number of tubular cysts in which spermatogenesis proceeds from the periphery towards the hilus.^ The excretory system of the gland consists of a number of ducts lined with cubic or cylindric epithelium. In the distal part of these ducts the cells (fig. 1) contain, besides secretion-granules, a large number of chondriosomes. These are mostly long chondrioconts running along the nucleus in a direction perpendicular to the basis of the cell and intertwining at both poles of the nucleus. This disposition reminds one somewhat of the structure of the cells of the tubuli contorti (Heidenhain's rods) or of the salivary ducts (Pfliiger's rods). The inner part of the cell is often free of chondriosomes and irregularly delimited, an appearance which may be due to the action of the fixing fluid.

In the cells lining the proximal part of the excretory ducts, the chondriosomes are all replaced by granules of pigment. This recalls an observation made by Prenant ('11) on the skin and cornea of the frog. Prenant found that the cells of both layers in the skin contain mitochondria and pigment-granules. In the upper layer the granules of pigment are located near the surface, the mitochondria in the lower part of the cell, w^hile in the deeper layer mitochondria and pigment-granules are mixed

' Degenerating cells are, as in other testicles and especially in invertebrates, b}' no means infrequent in Fundulus.

TESTICLE-CELLS OF FUNDULUS 137

together. In the cornea no pigment is present. If one studies the point of transition between cornea and skin, one can see how the mitochondria gradually take the place of the pigment-granules. This observation is interpreted by Prenant, apparently not without reason, as indicating the transformation of chondriosomes into pigment and in the same sense could be interpreted the conditions just described in" the excretory ducts of the fishtesticle.

The seminiferous cysts are reunited by thin sheets of connective tissues containing blood-vessels and cells. Some of these are conspicuous by their large size and by the presence of a great number of bacilli-shaped chondrioconts (fig. 2) ; others contain also granules which I am inclined to consider as secretion-products. In places where the connective tissue is somewhat more abundant, for instance in such stellar spaces as appear between the cross sections of the cysts, they usually build groups of two or more elements. The nearest interpretation of these cells is that they correspond to the interstitial cells of the ma nmalian testicle. Supposing I were right, this would be the first mention of them in fishes, or, as far as I know, the literature does not contain any mention gf interstitial tissue in this class of vertebrates: in fact Friedmann ('98) and Ganfini ('02) state positively that they could not find it.

The distal part of the cysts is occupied by cells which are obviously the stem of the whole seminal lineage and as such should be designated as spermatogonia. Since, as we shall see, several generations of spermatogonia can be distinguished, I would call these 'primary spermatogonia.' Their size is relatively large (fig. 3, two cells on the top row and two cells at the right). Each nucleus contains usually only one large, sharply delimited, spherical block of chromatin-. The eventual occurrence of multiple nucleoli is often accompanied by the presence of indentations (the process is just indicated in figure 3, in the cell of the top row, to the right), which are suggestive of direct division. Mitosis however was repeatedly observed (figs. 4 and 5). It would not be surprising if these indentations were indicative of a process described as occurring in the spermatogonia of

138 J- DUESBERG

Salamandra after the period of sexual activity (namely by Meves '91), as once that period over, the testicular conditions are very similar in both the amphibian and the fish.

The chondriosomes of the primary spermatogonia deserve special mention. In the resting cell they are numerous, coarse and irregular granules or rods. Most of them are located very close to the nucleus and cover its surface. This disposition might be interpreted in favor of Goldschmidt's chromidial theory. Such a claim however would be unfounded: Goldschmidt and his pupils basing themselves upon defective observations, expected to demonstrate that the chondriosomes of the germ-cells were formed during the growth-period and they have failed utterly.^ The continuity of the chondriosomes on the other hand has been demonstrated in a number of animals and is strongly supported for fishes by my observations on the fishembryo ('17).^ It is however far from my mind to deny the

^ For a complete historical and critical account of the chromidial theory, see the third chapter of my review ('12). Shaffer, who seems inclined to believe (p. 414) in a nuclear origin of the chondriosomes, gives as an argument that "in nearly all the growth-stages of the first spermatocytes, there is present a denser and more deeply staining perinuclear zone," formed by the chondriosomes. I should take exception to this statement, for it is characteristic, even if not quite general, that the male auxocytes have their chondriosomes accumulated at one pole of the nucleus, around the idiozome.

In a paper on the testicle of opossum, Jordan ('11) claims that he has demonstrated the discontinuity of the chondriosomes in the seminal cells. I have been investigating lately the same object and my observations are in direct contradiction with Jordan's claim: chondriosomes exist in abundance in all the stages of the evolution of the seminal cells.

Shaffer ('17) enters against the theory of the continuity of the chondriosomes in the following way; " (p. 423) the progressive increase in the amount of mitochondria (during the evolution of the seminal cells) seems to indicate that they are differentiation-products. Hence, if there is any genetic continuity between the mitochondria of successive cell-generations, it is only of a limited sort. The conception that the mitochondria present in the somatic cells are the direct descendants of those of the germ-cells, from which thej' have arisen, certainly has very little evidence in its favor." I must state that I entirely fail to see an argument against the continuity of the chondriosomes in the fact that their amount may increase. Concerning the continuity of the chondriosomes in the somatic cells with those of the germ-cells, -Shaffer overlooks apparently the numerous observations which have shown this continuity, from the egg at least to the embryonic cells. I limit myself to remind of my own observations on the bee,

TESTICLE-CELLS OF FUNDULUS 139

existence of nucleocytoplasmic exchanges, as the nucleus is certainly not a sort of impermeable rubber-vesicle enclosed in the cell. But it would be rash to base on the mere existence of such appearances as described above any definite conclusion. The arguments for the cytoplasmic nature of the chondriosomes I do not want to repeat here and refer the reader to former papers, limiting myself to state that no indications of a nuclear origin can be found in the staining reactions.^

During the mitotic division of the primary spermatogonia the shape of the chondriosomes changes somewhat: they round up and become more regular (figs. 4 and 5). Their location in the cell is also modified: at the stage of metaphase they surround the spindle (fig. 4) and later are found between the daughternuclei (fig. 5).'^

Next to these cells are others differing but slightly from them. They are somewhat smaller in size and their chondriosomes are not quite so coarse. These cells are assembled in rosettes of

the rabbit and quite lately on Ciona, where the chondriosomes form the material of the yellow crescent, the continuity of which has been demonstrated by Conklin.

^ The original colors of the preparations could not be reproduced in the plates; as is well known, they are, in acid fuchsin-methylgreen preparations, red for the chondriosomes and green for the chromatin; in Benda's preparations, dark purple for the chondriosomes and pale brown for the chromatin.

' Concerning the fate of the chondriosomes during the mitotic division of the spern.atogonia of Passalus, Shaffer expresses himself as follows (p. 410): "the spermatogonial cysts which are in mitotic activity, stand out very clearly in contrast with the resting cysts. This is because of their lighter staining capacity; whether this in turn is due to the partial disappearance of the mitochondria could not be ascertained." Shaffer quotes Buchner as having found that in Gryllotalpa vulgaris, the chondriosomes disappear during or just before celldivision and gives three possible explanations "for the partial loss of mitochondrial structure dating mitotic activity." Interesting though they may be, these explanations appear to me for the present useless, as, after my own experience, chondriosomes do not disappear during mitosis, no more in Gryllotalpa, as I have shown ('10), than in any other case I know of.

Payne ('17) quotes both Buchner and me and sees no reason why we should differ so much in our observations: "In this case, one or the other has certainly made a mistake." Between a negative result, however, and a positive one, there is, in my opinion, no room for hesitation. It must be added that since, Buchner has considerably modified his attitude towards the chromidial theory, as appears from a text-book he recently published.

140 J. DUESBERG

three or more (fig. 3 on the left below) . So unvarying are these features that I feel justified in considering these cells as a distinct generation of spermatogonia and term them 'secondary spermatogonia.' The primary and secondary spermatogonia are in close contact with each other, the cystic cavity being at these stages only virtual, in contrast with all later stages, when some room, in well fixed material, is left between the cells.

The spermatogonia belonging to a third generation are, if any, not much smaller than the secondary spermatogonia. In the nucleus several blocks of chromatin are present. The chondriosomes are granules, most of them regular, some larger and coarser. Instead of surrounding the nucleus, as in the preceding generations, they are all located at one of its poles (fig. 6). During mitosis a breaking-up into smaller granules appears to take place. Their behavior is the same as described above and is illustrated for the stage of metaphase by figure 7. In fact, the size of the spindle is in proportion to the size of the cell so large that the chondriosomes have to take whatever place they can in the cell-body, which is practically filled by the karyokinetic figure.

In the first spermatocytes (fig. 8) the polar location of the chondriosomes persists throughout the whole growth-period until the prophase of the first division and coincides as always with the polar field, while in the nucleus the usual structural changes take place. The chondriosomes are now granules all equal in size and regularly spherical and most of them are very closel}^ heaped together. It must be noted that during this so-called growthperiod the spermatocytes of Fundulus actually grow very little and that there is no evidence, as in other spermatocytes, of an increase in the mass of chondriosomes.

At the prophase of the first division the mitochondria become scattered all around the nucleus and, when the spindle is formed, they are as previously pushed towards the periphery of the cellbody and very close to it ; for here again the spindle is very large in proportion to the cell. I may mention in passing that the centrioles appear very conspicuously at the poles of the spindle (fig. 9). During the anaphase all the mitochondria are found

TESTICLE-CELLS OF FUNDULUS 141

between the daughter-nuclei (figs. 10 and 11). The same process is repeated during the second division (fig. 12). Though the cells are very small, it is easy enough to distinguish both mitoses owing to the following characteristics. The first spermatocytes are larger than the second ones. The spindle at the stage of metaphase is more slender in the second division. The number of chondriosomes decreases conspicuously. Finally the size and shape of the chromosomes as observed in Benda's material present a most distinctive character: in the first division they are unmistakably heterotypic.

The spermatids, which are exceedingly small, very soon form an axile filament. At first the mitochondria are scattered all around the nucleus but only for a short time. In the succeeding stage which is very characteristic and which, judging from its frequent occurrence in the preparations, lasts apparently a considerable period, all the mitochondria are found accumulated in one heap at the posterior pole of the nucleus where they surround the proximal part of the axile filament (fig. 13). A glance at these cells readily gives the impression that the number of their mitochondria is constant. When one attempts to count them however, one realizes that to obtain exact figures is almost impossible, for the granules are very small and not all in the same level. The numbers I found in the most favorable cases came very close to eight.

Further stages of spermiogenesis are characterized by changes in the mitochondria (which will be described below), the growth of the tail and the following modifications of the nucleus. First, the posterior side, which is in close contact with the mitochondria, becomes flattened or even somewhat concave (fig. 14). Its chromatic content then gradually accumulates at the periphery, with the exception of the posterior or flattened side, a process whose occurrence has been described several times in invertebrates and which begins in Fundulus at the stage represented by figure 14. The crust of chromatin thus formed assumes the outline of a horse-shoe, the space existing between the free ends of its branches being occupied by the mitochondria; from the same space emerges the axile filament (fig. 15 et seq.). Later,

142 J. DUESBERG

the head becomes somewhat elongated and the branches of the horse-shoe are by the same process brought nearer together (fig. 16, 17 and 18). At the same time the head loses its symmetry inasmuch as it becomes somewhat curved along its antero-posterior axis and its posterior facet becomes oblique, instead of being perpendicular, to the same axis. From this time on we can distinguish what I have, arbitrarily of course, termed face- views (figs. 16 and 21) and side-views (figs. 17, 18 and 20) of the spermatozoon.

All the modifications of the head are more easily followed on acid fuchsin-methylgreen preparations than on Benda's, for methylgreen gives a sharper stain for chromatin than sodiumsulfalizarinate. In material fixed with Regaud's fluid the clear middle-space of the head appears very conspicuous even in the last stages; but curiously enough, as soon as the spermatozoa have reached the excretory ducts, the staining reaction changes and the head takes up acid fuchsin instead of methylgreen. In preparations made from material fixed with Benda's fluid the ripe spermatozoa, that is, those which have reached the excretory ducts, appear somewhat different from those fixed in Regaud's fluid. In a side-view (fig. 20) the clear middle-space appears only indistinctly. In face- views (fig. 21) on the other hand, the same space is very conspicuous and sharply delimited, and has the appearance of a canal running from the posterior to the anterior extremity of the head.

During this period changes take place in the mitochondria also. Their number decreases and their size increases: in other words, there is a fusion of granules. This process can be best followed in Regaud's preparations for the reason that the thin sheet of protoplasm which keeps the mitochondria in place (figs. 14 and 15) and which is hardly visible in Benda's preparations, swells in Regaud's fluid as do also the mitochondria themselves. Consequently, the cells and the granules are somewhat larger than in Benda's preparations and they are more scattered. These differences are well illustrated by figures 15 and 19, which represent approximately the same stage, after Regaud's and Benda's fixation respectively. Thus in figure 15 we can count

TESTICLE-CELLS OF FUNDULUS 143

exactly six granules while Benda's preparations of the same stage (fig. 19) show an undecipherable heap of mitochondria. Later when the asymmetry of the head has become conspicuous, we find almost invariably four mitochondria (fig. 16), disposed with remarkable regularity upon the posterior facet of the head. Finally in the ripe spermatozoon the number is still more reduced, usually to three. Here Benda's material is more serviceable than Regaud's owing to the change in the staining reactions of the head mentioned above. A comparison of the different stages of this evolution, as they appear after fixation in Regaud fluid, shows that the increase in volume of the mitochondria is not directly proportional to their decrease in number (figs. 13 to 18) ; and, as there is no evidence of an elimination of mitochondria, one would be led to believe in a strong condensation of the chondriosomal substance. This conclusion is however not supported by Benda's preparations and I am forced to admit that the swelling produced by the formalin-bichromate mixture is greater in the first stages of spermiogenesis than in the later ones.

As stated above, the average number of mitochondria in the ripe spermatozoon, as counted in Benda's preparations, is three. They are especially conspicuous in face- views (fig. 21), where they are found regularly disposed on the posterior facet of the head. Occasionally spermatozoa are found with four, five or even six granules taking the chondriosomal stain. The majority of these granules are undoubtedly mitochondria and in such cases the fusion has, for some unknown reason, apparently not proceeded normally. Whether it is completed later is difficult to say. It is probable also that occasionally the centrioles are stained, for in certain cases it was possible to recognize a relationship between the proximal extremity of the axile filament and a small granule stained like a chondriosome (fig. 20). I cannot give any definite information about the behavior of the centrioles during the spermiogenesis of Fundulus,^ but there is no doubt that they are located in that region.

One thing however is certain: that their behavior is very different from the same in selachians (Suzuki, '98).

144 J. DUESBERG

Again as in many and perhaps all cases, the last stages of spermiogenesis bring about a change in the behavior of the chondriosomes towards reagents. It is well known that, in the mammalian testicle for example, the chondriosomes become more and more resistant to acetic acid as spermiogenesis progresses.^ The test of this resistance was not made here, but it was found that the chondriosomes of the last stages are structures much less labile than the chondriosomes of the early stages and are consequently much easier to bring into evidence. « 

The preceding description of the spermatozoon of Fundulus agrees in the main with Retzius' observations on the spermatozoon of other teleosts, though differing in the details. It helps at the same time to emphasize the similarity in structure between these spermatozoa and those of a large number of invertebrates, while the spermatozoa of selachians and of the higher vertebrates are widely different.

From the same description it also appears very probable that the male chondriosomes, owing to their close contact with the nucleus, are carried into the egg at the time of fertilization. Though this can be ascertained only by the study of the fertilizing process, the evidence accumulated by an imposing number of observations made upon almost all classes of animals, especially in recent years, is certainly very much in favor of the theory according to which the penetration of the male chondriosomes into the egg is a general phenomenon. Shaffer who mentions only Meves' observations on Ascaris and Vander Stricht's on the bat, overlooks the largest part of this evidence. That Lillie ('12) found in Nereis that the 'middle-piece' and the tail of the spermatozoon do not enter the egg does not prove that the chondriosomes are not carried into it.

I still believe, as in 1915, that the real objection to the admission that the male chondriosomes play a role in heredity is to be found in Meves' observations on the echinoderm-embryo ; why their admitted chemical composition should plead against

^ I found recentl}^ that the same changes take place in the spermatids of opossum.

TESTICLE-CELLS OF' FUNDULUS 145

such a role, as Cowdry ('16, p. 437) seems to believe, I fail entirely to see. Concerning the hypothesis of their motile function which, first formulated by Benda, reappears occasionally in the literature, I do not see that any arguments have been brought forward in its favor, nor is there any clear expression of how we should imagine this function. Benda considered his 'mitochondria' as contractile bodies : how can this conception be applied to the spherical chondriosomes of the spermatozoa of so many invertebrates and of Fundulus? Furthermore, those who advocate this hypothesis entirely overlook two groups of observations, which we have to accept as long as their inexactitude has not been demonstrated : first, Meves' experiments on the spermatozoon of Salamandra and second, the observations of a number of authors, lately Koltzoff's, on the spermatozoa of decapods (see Duesberg, '12, p. 687).

Finally a few words concerning the occurrence of a constant number of chondriosomes in male germ-cells.

The first indication of this was given by Meves ('00) who found that the small spermatocytes (i.e., as the apyrene generation) of Paludina vivipara contain on the average eight loopshaped chondriosomes. Numerations made on spermatids of the same generation a short time after the second division likewise revealed an almost unvarying number of chondriosomes,. this time four.

Two other cases, much more striking, have been described lately, both in arachnoids, the first one by Sokolov ('13), the other by Wilson ('16).

In the spermatogonia and in the young spermatocytes of Euscorpius carpathicus Sokolov describes mitochondria which soon by confluence form filaments. Later rings appear, which are probably formed by fusion of the free ends of the filaments of the preceding stages. The average number of these rings is twentyfour. During mitosis they are not divided as is the case in the small spermatocytes of Paludina, but are segregated into two equal groups between the daughter-cells. Thus each spermatid contains one quarter of the number of rings, on the average six.

146 J. DUESBERG

The result of this process is an obvious and measureable reduction of the chondriosomal mass at the end of the divisions of maturation and Sokolov sees in it a confirmation of the views I have expressed as the result of my study of the behavior of the chondriosomes in the spermatocyte-divisions of the rat ('07) .

Wilson has studied the chondriosomes in the spermatogenesis of two other species of scorpions, Opisthacanthus elatus (Southern California) and Centrums oxilicauda (Southern Arizona). The results obtained from the study of the first named species are very similar to those of Sokolov. Each spermatocyte contains about twenty-four hollow spheroidal bodies, which are segregated by the spermatocyte-divisions into four approximately equal groups. Each spermatid thus receives as a rule six chondriosomes (in 73 per cent of the cases, on 200 numerations), sometimes five (in 16 per cent of the cases) or seven. No other numbers were observed. In the Arizona-scorpion, the process is quite different. All the chondriosomal material becomes concentrated in a single definite body in the form of a ring. This ring divides during mitosis in such a way that each spermatid receives exactly one-fourth of its substance, the process taking place with a precision that is comparable to that seen in the distribution of the chromosome material."

As Wilson points out the body in question represents a hitherto undescribed type of chondriosome. The occurrence of this interesting process makes one speculate as to what the field of spermatogenesis, though so widely explored, still has in store for the investigator. It appears to me that conditions similar to those found in scorpions, at least to those found in Euscorpius and in Opisthacanthus, could be expected in the histogenesis of these spermatozoa in which, as stated above, the chondriosomes are represented by a constant or approximately constant number of well-defined granules. There is some indication of a similar process in Fundulus, but the small size of the cells unfortunately makes an exact numeration impossible. The same difficulty would certainly be met with in the study of the seminal cells of other teleosts as well as of echinoderms and celenterates ; molluscs and worms, however, would probably be a favorable material.

TESTICLE-CELLS OF FUNDULUS 147

BIBLIOGRAPHY

BoNNEViE, Kr. 1907 Untersuchungen iiber Keimzellen. 2. Physiologische

Polyspermie bei Bryozoen. lenaische Zeitschr., Bd. 42. CowDRY, E. V. 1916 The general functional significance of mitochondria.

Am. Jour. Anat., vol. 19. DuESBERG, J. 1907 Der Mitochondrialapparat in den Zellen der Wirbeltiere

und Wirbellosen. I. Arch, flir mikr. Anat., Bd. 71.

1910 Nouvelles recherches sur I'appareil mitochondrial des cellules

seminales. Arch, fiir Zellf., Bd. 4.

1912 Plastosomen, "Apparato reticolare interno" und Chromidial apparat. Ergeb. der Anat. und Entwickl., B. 20.

1915 Recherches cytologiques sur la fecondation des Ascidiens et sur

leur developpement. Contr. to Erabr. Carnegie Inst., 223.

1917 Chondriosomes in the cells of fish-embryos. Am. Jour.

Anat., vol. 21. Field, G. W. 1895 On the morphology and physiology of the echinoderm spermatozoon. Journ. INIorph., vol. 2. Friedmann, Fr. 1898 Beitriige zur Kenntniss der Anatomic und Physiologic

der mannlichen Geschlechtsorgane. Arch. fiir. mikr. Anat., Bd.

52. Ganfini, C. 1902 Struttura e sviluppo delle cellule interstitiali del testicolo.

Arch. ital. di Anat. e di Embr. vol. I. Jordan, H. E. 1911 The spermatogenesis of the opossum (Didelphys virgini ana), with special reference to the accessory chromosome and the

chondriosomes. Arch, fiir Zellforsch., Bd. 7. Lewis, M. R. 1917 The effect of certain vital stains upon the development of

the eggs of Cerebratulus lacteus, Echinorachnius parma and Lophius

piscatorius. Anat. Rec, vol. 13. LiLLiE, F. R. 1912 Studies of fertilization in Nereis. Jour. Exp. Zool., vol.

12. Meves, Fr. 1891 Ueber amitotische Kernteilung in den Spermatogonien des

Salamanders und Verhalten der Attraktionsphare bei derselben.

Anat. Anz., Bd. 6.

1900 Ueber den von la Valette St. George entdeckten Nebenkern

(Mitochondrienkorper) der Samenzellen. Arch, fiir mikr. Anat., Bd.

56.

1903 Ueber olygopyrene und apyrene Spermien und ihre Entstehung,

nach Beobachtungen an Paludina und Pygeara. Arch, fiir mikr.

Anat., Bd. 61.

1912 Verfolgung des sogenannten Mittelstiickes des Echiniden spermiums im befruchteten Ei bis zum Ende der ersten Furchungsteil ung. Arch, fiir mikr. Anat., Bd. 80. Payne, F. 1917 A study of the germ-cells of Gryllotalpa borealis and Gryl lotalpa vulgaris. Jour. Morph., vol. 28. PiCTET, C. 1891 Recherches sur la spermatogenese chez quelques inverte bres de la Mediterranee. Mitt, aus der zool. Station zu Neapel, Bd.

10.

148 J. DUESBERG

PrenaNT, A. 1911 Pr(?parations relatives aux mitochondries. Comptes-Rendus

Assoc. Anat. Paris. Retzius, G. 1904 a Zur Kenntnis der Spermien der Evertebraten. I. Biol.

Unters., N.F., Bd. 11.

1904 b Zur Kenntnis der Spermien der Evertebraten. Verhdl. Anat. Gesellsch. Jena.

1905 a Zur Kenntnis der Spermien der Evertebraten. 2. Biol. Unters, N.F., Bd. 12.

1905 b Zur Kenntnis der Spermien der Leptokardier, Teleostier und Ganoiden. Ibid.

1906 a Die Spermien der Gastropoden. Biol. Unters, N.F., Bd. 13. 1906 b Die Spermien der Enteropneusten und der Nemertinen. Ibid.

1906 c Die Spermien der Turbellarien. Ibid.

1906 d Die Spermien der Bryozoen. Ibid.

1909 a Die Spermien von Aurelia aurita (L). Biol. Unters., N.F.,

Bd. 14.

1909 b Die Spermien der Nereiden. Ibid.

1909 c Zur Kenntnis der Spermien der Elasmobranchier. Ibid.

1910 a Zur Kenntnis der Spermien der Echinodermen. Biol. Unters., N.F., Bd. 15.

1910 b Weitere Beitrage zur Kenntnis der Spermien mit besonderer

Beriicksichtigung der Kernsubstanz. Ibid. ScHREiNER, A. AND K. E. 1905 Ueber die Entwicklung der miJnnlichen Ge schlechtszellen von Myxine glutinosa. Archives de Biologic., vol. 21.

1908 Zur Spermienbildung der Myxinoiden. Arch, fiir Zellf., Bd. I. Shaffer, E. L. 1917 Mitochondria and other cytoplasmic structures in the

spermatogenesis of Passalus cornutus. Biol. Bull., vol. 32. SoKOLOV, I. 1913 Untersuchungen tiber die Spermatogenese bei den Arachni den. I. t'ber die Spermatogenese der Skorpione. Arch, fiir Zellf. ,Bd.

9. Suzuki, B. 1898 Notiz uber die Entstehung des Mittelstlickes der Samenfaden

von Selachiern. Anat. Anzeiger, Bd. 15. Wilson, E. B. 1916 The distribution of the chondriosomes to the spermatozoa

in scorpion. Science, N.S., 43 and Proceedings of Nat. Acad, of

Sciences.

PLATES

149

THE AMERICAN JOURNAL OF ANATOMY, VOL. 23, NO. 1

EXPLANATION OF FIGURES

All figures were outlined with a Zeiss camera-lucida, at the level of the stage of the microscope. Lens used: Zeiss apochr. imm. 1 m.m., 5; ocular 12. Artificial light (gas).

PLATE 1

EXPLANATIOX OF FIGURES

1 Fundulus majalis. Fixation: Benda, without acetic acid. Stain: Benda. Epithelium of an excretory duct.

2 Fundulus heteroclitus. Fixation: Benda. Stain: Benda. Supptised interstitial cells.

3 Fundulus majalis. Fixation: Benda, without acetic acid. Stain: Benda. Group of primary and secondary spermatogonia.

150

TESTICLE-CELLS OF FUNDULUS

J. DUESBERG

PLATE 1

151

PLATE 2

EXPLANATION OF FIGURES

4 and 5 Fundulus heteroclitus. Fixation: Benda. Stain: Benda. Metaphase and anaphase of the mitotic division of primary spermatogonia.

6 Same material. Tertiary spermatogonium.

7 Same material. Tertiary spermatogonium : metaphase.

8 Fundulus majalis. Fixation: Benda, without acetic acid. Stain: Benda. First spermatocyte.

9 and 10 Same material. ^Nletaphase and anaphase of first division of maturation.

11 Fundulus heteroclitus. Fixation: Regaud. Stain: acid fuchsin-methjdgreen. Anaphase of first division of maturation.

12 Same material. Anaphase of second division of maturation.

13 to 18 Same material. Six stages of spermiogenesis; in none is the tail represented in its full length. 16 and 17 are respectively face-view and side-view of approximatively the same stage.

19 Fundulus heteroclitus. Fixation: Benda. Stain: Benda. Group of spermatids in a cyst.

20 and 21 Fundulus majalis. Fixation: Benda, without acetic acid. Stain: Benda. Spermatozoa from the excretory ducts (the tail is not represented in its full length). 20: side-view; 21: face-view.

152

TESTICLE-CELLS OF FUNDULUS

J. DUESBERG

PLATE 2

.^4^

%'

i'^i^

p

0- 13

2C> 21

t^

153

author's abstract of this paper issued by thk bibliookaphic service, decemher 1

THE POSITION OF THE INSERTION OF THE PECTO RALIS MAJOR AND DELTOID MUSCLES ON

THE HUMERUS OF MAN

ADOLF H. SCHULTZ

Carnegie Institution of Washington

THREE FIGURES

The metrical determination of the position of the attachments of muscles to bones is a problem which affords a contribution to topographicaJ anatomy. It is also of importance from the standpoint of musculo-mechanics, because measuring the insertions of muscles is analogous to the determination of the lengths of leverage of the body. Since such an investigation promises to give information regarding differences or equalities of race or sex, as well as of the two halves of the body, it is of no less interest to the anthropologist. As far as the author can determine from a study of anatomical and anthropological literature, no measurements of the insertions of muscles have as yet been undertaken. In approaching this problem one is working in a new field of osteometry, where it becomes necessary to treat the bone not separately but in conjunction with the associated muscles, W'hich have been so neglected in anthropometry.

The following study deals with the insertion of the pectoralis major and deltoid muscles. The measurements were made on the right and left arms of one hundred and five bodies. Fortysix of these bodies were obtained from the University of Maryland in Baltimore, forty from the Jefferson Medical College in Philadelphia and nineteen from the Johns Hopkins Medical School in Baltimore. The author wishes here to express his appreciation to r)rs. W. H. Lewis, J. P. Schaeffer, J. Holmes Smith and J. W. Holland for their kindness in permitting the use of this material. All of the subjects measured were adults; juvenile and senile ones were excluded. It is regrettable that the sexes

155

156 ADOLF H, SCHULTZ

were very unequally represented, for the females numbered only twenty-seven, as against seventy-eight male subjects. A greater uniformity occurred in race, as there were fifty-one white and fifty-four colored bodies. The author wishes to call attention to the fact that the term race is used in its widest sense in the present paper, because both the white and colored inhabitants of America have originated from nmnerous races in a limited sense. In negroes one frequently witnesses a more or less extensive admixture of white blood; in cases where there was evidence of a too great intermingling with the white element the material was discarded.

The position of the muscle insertion was compared with the length of the humerus by measuring the distance of the most proximal and the most distal point of attachment from the proximal end of the bone, and further by determining the arithmetical mean of these distances in percentage of the length of the humerus. For this purpose we need first of all six exact points of measurement, a proximal and a distal point on the humerus, two corresponding points on the pectoralis major and two more on the deltoid. The two points on the humerus are found by measuring the length of the bone, choosing the distance of the highest point of the caput humeri from the lowest point of the capitulum and measuring parallel to the axis of the bone (fig. 1, points I and II). The points of measurement for the pectoralis major muscle are the most proximal and the most distal points of its insertion on the crista tuberculi majoris (fig. 1, points III and IV) ; as a rule they are readily determined. Occasionally the distal portion of the insertion is intimately connected with the tendon of the deltoid muscle and the distal point can only be obtained after careful separation of these structures. In a, limited number of cases the dorsal reflected portion of the muscle was observed to form a narrow tendinous band in the region where it spreads out proximally to join the tendinous lining of the sulcus intertubercularis (in figure 1 such an instance is indicated at a). In such cases this prolongation was ignored and the point of measurement taken at its distal end. The lower point of measurement of the deltoid is comparatively easy to

PECTORALIS MAJOR AND DELTOID INSERTION

157

Fig. 1 Diagram of the points of measurement and distances on a right humerus seen from in front.

158 ADOLF H. SCHULTZ

ascertain, namely as the most distal point of the insertion on the tuberositas deltoidea (fig. 1, point VI). The most proximal point of insertion is frequently concealed by the body of the muscle and it is necessary therefore to remo\'e it partially. In doing this great care should i^e exercised as the deltoid is usually attached at its uppermost end by very delicate strands (fig. 1, point V). The distance between each of these four points and the highest point of the head of the humerus was measured parallel to the axis of the bone, similar to the longitudinal measurement of the humerous mentioned above and therefore these measurements are projections.

The measuring instrument employed was a modified small anthropometer of Martin (Stangenzirkel). This instrument is composed of a ruled metal bar or beam, possessing two arras at right angles to it, one of which is firmly attached to the end, the other movable in the direction of the bar, while both are movable at right angles to the latter. The modification consists merely in the addition of a third arm from another instrument of the same kind, which can also be moved both in the same direction and at right angles to the main axis (fig. 2).

First one measures the length of the humerus with the two outermost arms of the instrument holding the bar parallel to the axis of the bone, then the middle arm is approximated in turn to the four points of muscle insertion as defined above. This is performed by moving the arm up and down as required, shortening or lengthening it, simultaneously rotating the entire instrument around the axis of the humerus if necessary. Readings are taken each time on the ruled bar and correspond with the measurements two, three, four and five in figure 1. Indices for the relative position of the middle point of each muscle insertion were obtained b}- the following formulae:

nieasurcniont 2 + measurement 3

2

X 100 lor (he pectoralis major

measurement 1

measurement 4 + measurement 5

measurement 1

X 100 for the deltoid

PECTORALIS MAJOR AND DELTOID INSERTION

159

The greater these indices of position, the more distal, the smaller, the more proximal is the insertion of the muscle. Following is a short description of the mathematical treatment of the length of the humerus and the indices which have been used in this paper. A more detailed explanation of these methods, which are absolutely necessary for an understanding of the

Fig. 2 Small anthropometer with three parallel movable arms.

measurements on a large number of individuals, is to be found in the Textbook of Anthropology by R. Martin, Jena, 1914, p]). 63-103.

The average (M) is the arithmetical mean of the individual

values (F) of a group (/?. = number of individuals): M = -i;F.

The standard deviation (a) is the square root of the average of

160 ADOLF H. SCHULTZ

the squares of the deviations of the individual values from the average of the row and expresses the absolute variability:

(T = W-S(F — M)-. The variation coefficient (v) expresses the

standard deviation in percentage of the average, whereby a

criterion for the relative variability is obtained : v = -—-- . The

correlation coefficient (r) affords a means of determining the law,

according to which two characteristics combine. It is the sum

of the products of the deviations of the two characteristics from

the corresponding averages taken for each individual, divided by

the product of the number of individuals and the two standard

2 (x — X) (y — Y)

deviations : r = — — ~ . A complete correlation

na^ ay

exists when r = 1. If r = 0, no relation prevails between the two characteristics. A positive correlation coefficient indicates a change of the characteristics in the same direction, a negative one, in the opposite direction. Finally, to test the degree of exactness of the above formulae, the probable error (E) was determined by the following formulae:

EiM) = ± 0.6745 -J- for the average.

■\ n

E {a) = ±0.674:5—; — •- for the ptaudard deviation.

V2ft

V

E (v) = ±0.6745— — for the variation coefficient.

V2//.

If r > 10, the hist forinuhi must be multiplied bv -v'l + 2 ( — - )

- \ VlOO/

E (r) = ±0.6745 — r^— for the correlation coefficient

■\ n

The relation of the insertion of the muscles to the length of the humerus makes a short prehminary discussion of this absolute measurement necessary. Table 1 is a compilation of the averages and the conditions of variability of the length of the two hiuidred and ten humeri, which were measured. The extremes of these measurements range from 260 to 367 mm. The humerus in male whites is on the average 26 mm., in male negroes 31.8 mm.

PECTORALIS MAJOR AND DELTOID INSERTION

161

TABLE 1

Averages, standard deviations, variation coefficients, their probable errors and ranges of variation for the length of the humerus

RACE

SEX

NUMBER

SIDE

M ± E (M)

a ± B (o-)

V d= E (r)

Minimum

Maximum

cT

40

Y.

316.3±1.71

15.94±1.22

5.04±0.38

283

347

o^

40

1.

316.5±1.82

17.05±1.29

5.40±0.41

283

352

Whites <

d^

80

r. 1.

316. 4± 1.25

16.50±0.87

5.22±0.27

283

352

9

11

r.

293.1±2.58

12.65±1.81

4.32±0.62

269

309

9

11

1.

287.7±2.02

9.92±1.42

3.44±0.50

267

303

9

22

r. 1.

290.4±1.67

11.69±1.19

4.03±0.41

267

309

c^

38

Y.

326.2±1.87

17.18±1.34

5.27±0.41

290

367

&

38

1.

323. 5 ±2. 02

18.50±1.44

5.71±0.44

283

365

Negroes . . . <

c^

76

Y. 1.

324 8±1.39

17.89±0.98

5.50±0.30

283

367

9

16

r.

294.6±2.45

14.51±1.74

4.92±0.59

266

321

9

16

1.

291.5±2.51

14.84±1.78

5.10±0.61

260

312

9

32

r. 1.

293.0±1.77

14.75±1.24

5.03±0.42

260

321

longer than in females. The averages in negroes exceed in both sexes the corresponding values for whites. The division of table 1 into separate rows for the right and left humerus shows that the variability is greater on the left side except in the group of white females of which the number measured was quite small. Furthermore it shows that the white males, who possess the same average length of the humerus on both sides, form an exception to the rule of the greater length of the humerus on the right side. Table 2, which gives a survey of the absolute and

TABLE 2

Absolute and relative numbers of individuals uiith equal and different lengths of the humeri and average differences of the individual asymmetries (mm.)

SEX

9 9

BOTH SIDES EQITAL

RIGHT SIDE LONGER

AVERAGE DIFFERENCE IF

Right

side

longer

Left

side

longer

Whites 1

Negroes <

10=25.0% 0= 0.0%

8 = 21.0%

7 = 43.8%

17 = 42.5%

9 = 81.8%

22 = 58.0% 9 = 56.2%

13 = 32.5%

2 = 18.2%

8 = 21.0% 0= 0.0%

3.88 7.67

5.73 5.44

5.62 5.00

3.25

162

ADOLF H. SCHULTZ

relative number of cases possessing humeri of equal and different lengths and the average differences of the individual asymmetries, shows that 32.5 per cent of white males have a longer left humerus. It also demonstrates that in white males the differences in favor of the left side are on the average greater than those on the right, which is not the case in the other groups. The greatest absolute asymmetry occurred in a negro whose right humerus exceeded the left in length by 23 mm.

TABLE 3

Averages, standard deviations, variation-coefficients, their probable errors and ranges of variation for the position index of the insertion of the pectoralis major m uscle

Whites

Negroes

SEX

XUMBER

SIDE

f ^

40

r.

cf

40

1.

d^

80

Y. 1.

9

11

r.

9

11

1.

L 9

22

r. 1.

I ^

38

Y.

d"

38

1.

cf

76

r. 1.

9

16

r.

9

16

1.

L 9

32

r. 1.

M ± E {M)

a± E (o-)

28. 37 ±0 17 1.5o±0.12

■28.50±0.16 1.49±0.11

28 43±0 11 1 o2±0.08

26 37±0.35 1.74±0 25

26 35 ±0.56 2.73±0.39

26.36±0.33 2.29±0 23

28 27±0.19 1.75±0.14

27.99±0.17 1 57±0.12

28.13±0.13 1 67±0 09

26 82 ±0 32 1 89±0 23

26 45±0 3l| 1.82±0 22

26.6]±0 22 1.86±0.16

E (v)

5.46±0.41

5 23±0.40 5.35±0.28 6.59±0.94

10.34±1.48 8.67=t0.88

6.18±0.48 5.61=t0.44 5.94±0.33 7.05±0 85

6 89±0.83 6.99±0.59

MINI- MAXMUM MUM

24.3 25.3 24.3 21.9 21.3 21.3

26.1 25.1 25.1 23.1 22.3 22.3

31.3 31.8 31.8 28.3 29.5 29.5

35.2 32.6 35.2 30.9 30.3 30.9

The averages and the conditions of variability of the index of position for the middle of the insertion of the pectoralis major muscle are given in table 3. This index differs in the entire material between 21.3 and 35.2. Expressing this in terms of the mechanics of levers, one can state that in the adult the lifting arm of the musculus pectoralis major is related to the carrying arm — the length of the humerus — in a ratio varying from 21.3: 100 to 35.2: 100. In other words the relation of the lever arms may differ by almost 14 per cent of the length of the carrying arm, and this expressed in an absolute number equals on the average about 45 mm. A different proi:)()rtion of the lever arms influences not onlv the force of the muscle hut also the movement

PECTORALIS MAJOR AND DELTOID INSERTION 163

of the lever, if the shortening of the muscles is equal. This can be readily seen from the diagram (fig. 3) A —B represents the humerus, its caput at A. C and D correspond to the two most extreme points of insertion of the pectoralis major. 1 and 2 indicate the two appertaining muscles. Should the latter shorten by the same amounts C — C' = D' — D' , than the lower end of the humerus B is moved more extensively by muscle 1 (to B") than by muscle 2 (to B'), for instance the humerus is turned through a greater angle when the muscles are contracting equally by the more proximal one, and consequently also more quickly, A more distally situated pectoralis major would have to contract more in order to pull the arm forward to a certain

D'-/--..C'

B ' * i — '^'-^^-'- A

D C

Fig. 3 Diagram of the movements of the humerus with equal shortening of the pectoralis major muscle at different points of attachment.

angle than would be necessary if it were more proximally attached. With increased contraction, however, a muscle loses in tension and consequently the greater shortening of the more distal muscle diminishes the advantage of its favorable lever arm.

In the group of whites as well as in the negroes, the averages of the index of position in the males exceed those of the females, the differences being 2.07 and 1.50 respectively. Since the probable errors of these averages are only small, this sexual difference, such as that the female possesses a more proximally attached pectoralis major muscle, must be considered as a rather essential and definite one. It is not only of interest in connection with the above mentioned consideration of musculo-mechaniscs, but also

164

ADOLF H. SCHULTZ

indicates that the female arm is looser, that is the perpendicular diameter of the axilla in the female is relatively shorter since the caudal edge of the pectoralis major at its lateral end represents the lower border of the axilla. The average of both sexes in the whites hardly differs from that found in the negroes; the two races are alike therefore in regard to the position of the insertion of the pectoralis major. The variation coefficient of the index is always rather high and even exceeds 10 in one case. The conclusion can be drawn from this that the position of the attachment of the pectoralis major can be only slightly influenced by the length of the humerus, since the index connecting these two

TABLE 4 Absolute and relative numbers of individuals ivith symmetrical and asymmetrical

position of the pectoralis major insertion and aver

jges of the indi

vidual

differ

ences of the position index

AVER.A.GE

RACE

SEX

THE SAME POSITION ON BOTH

POSITION ON THE RIGHT MORE

POSITION ON THE LEFT MORE

DIFFERENCE IF MORE DIST.\.LLT

&

SIDES

DISrAL

DIST.U,

on the right

on the left

Whites 1

1 = 2.5%

17 = 42.5%

22=55.0%

1.38

1.29

9

= 0.0%

4 = 36.4%

7 = 63.6%

2.17

1.21

Negroes <

9

2 = 5.2% = 0.0%

18 = 47.4% 13 = 81.2%

18 = 47.4% 3 = 18.8%

1.70 62

1.10 0.73

is quite variable. In order to throw some light on the question concerning the relationship of the point of attachment and the strength of the muscle, the individuals of each group were divided into four subgroups, namely into weak, medium, strong and very strong ones. Positive and negative variants of the index of position were found to be indiscriminately distributed among the four subgroups, in whites as well as in negroes and in males as well as in females. The strength of the muscle has therefore no influence on the position of the attachment. Table 4 shows a grouping of the absolute and relative number of individuals with symmetrical and asymmetrical position of muscle attachment, and the averages of the individual differences in the index of position. The position of attachment of

PECTORALIS MAJOR AND DELTOID INSERTION 165

the pectoralis major muscle was the same on both sides in onlythree out of one hundred and five individuals. The unusually large percentage of asymmetrical cases is on the average equally distributed on the two sides. One finds only small differences between the averages on the right and left side in table 3. The largest individual asymmetry was found in a negro whose index of position was 6.0 greater on the right than on the left side.

The index which has just been discussed gives a clear idea of the position of the median point of the muscle insertion, and it will therefore be of interest to devote our attention briefly to the length of the insertion of the pectoralis major, from which the median point was obtained. The absolute value of this insertion length is represented by the difference between measurement 2 and 3 in figure 1. In order to make this measurement independent of the individual size of the upper arm it has been expressed in percents of the humerus length. The formula of this relative measurement is as follows :

measurement 3 — measurement 2

XlOO

measurement 1

The averages and the conditions of variability of this index are tabulated in table 5. One notices a tremendous range of variation from 8.8 to 23.1, and the variation coefficients also are unusually large. It seems inadvisable therefore to attach any particular significance to the slight differences in sex and race, such as the relatively longer attachment of the muscle in females and in whites. There is no correlation between the relative insertion length and the muscle strength nor the position of the insertion. The measurement which has just been discussed is somewhat longer in whites on the right side, and in negroes on the left. There is a very marked tendency to asymmetry in the relative insertion lengths in the different individuals, as has already been found to be the case for the position of the insertion. The relative attachment length was equal on both sides in only four cases, and in only one case did the absolute length of attachment show no asymmetry.

THE AMERICAN JOUBMAL OF ANATOMY, VOL. 23, NO. 1

166

ADOLF H. SCHULTZ

TABLE 5

Averages, standard deviations, variations-coefficients, their probable errors and ranges of variation for the relative length of the insertion of the pectoralis major mtiscle

RACE

SEX

'.NUMBER

SIDE

M ± E (M)

o^ E (o-)

V ^ E (lO

MINIMUM

MAXIMUM

d'

40

r.

16.84±0.25

2.37^0.18

14.11±1.09

9.2

23.1

&

40

1.

16.32±0,25

2.35±0.18

14.42±1.12

11.5

20.8

Whites . . . . <

&

80

r. 1.

16.58±0.18

2 36±0.12

14.22±0.77

9.2

23.1

9

11

r.

16.95±0.39

1. 94=^0.28

11.48±1.66

13 6

20.3

9

11

1.

16. 53 ±0.50

2.45±0.35

14.85±2.16

12 9

21.5

9

22

r. 1.

16 74±0.32

2 22±0.23

13.29±1.38

12.9

21.5

c^

38

r.

16.13±0.38

3.52±0.27

21.86±1.77

8.8

22.7

cf

38

1.

16.30±0.24

2.18±0.17

13,37±1.06

10.5

20.2

&

76

r. 1.

16.21±0.23

3.02±0.16

18.64±1.02

8.8

22.7

9

16

r.

15.90±0.41

2.42±0.29

15.22±1.88

12.3

21.9

9

16

1.

16.88±0.38

2. 27 ±0.27

13.43±1.64

12.0

20.4

9

32

r. 1.

16.39±0.28

2.36±0.20

14.39±1.23

12.0

21.9

The averages and the conditions of variation of the index, which expresses the relative position of the middle point of the insertion of the deltoid muscle, are given in table 6. The variation extends from 34.0 — 46.5, that is it equals 31 per cent of the middle value of the two extremes and therefore remains

TABLE 6

Averages, standard deviations, variation-coefficients, their probable errors and ranges of variation for the position index of the insertion of the deltoid muscle

RACE

SEX

NUMBER

SIDE

M ^E (.W)

<j ^E {(t)

V ^ E (t))

MINIMUM

MAXIMUM

[•

' &

40

r.

40.45±0.22

2.03±0.15

5.02±0.38

37.2

44 8

d"

40

1.

41.17±0.19

1.80±0.14

4.37±0.33

37.5

45.6

Whites . . . . <

d

80

r. 1.

40.81±0.15

1.94±0.10

4.76±0.25

37.2

45.6

9

11

r.

39.35±0.52

2.57±0.37

6.52±0.93

34.0

42.5

9

11

1.

40.61±0.42

2.06±0.29

5.07±0.72

36.4

42.9

9

22

r. 1.

39.98±0.34

2.41±0.24

6.03±0 61

34

42.9

r

d

38

r.

40.40±0.24

2.22±0.17

5.50±0.43

34.0

44.7

d

38

1.

40.52±0.22

2.00±0.16

4.94±0.38

36.2

44.6

Negroes . . . <

&

76

r. 1.

40.46±0.16

2.12±0.12

5.24±0.29

34.0

44.7

9

16

r.

40.64±0.48

2.86±0.34

7 04±0.84

34 3

46.5

9

16

1.

41.11±0.42

2 50±0.30

6.08±0 73

36.1

45

9

32

r. 1.

40.87±0.32

2 70±0.23

6 60±0.55

34 3

46.5

PECTORALIS MAJOR AND DELTOID INSERTION 167

considerably less, than the variability of the position index of the pectoralis major, the variation of which equaled 49 per cent of its mean. The last named index shows in every group a greater variation coefficient than the corresponding ones in table 6. Therefore the deltoid possesses a more constant position of insertion than the pectoralis major muscle. Judging from the averages of the position index the attachment of the deltoid muscle must be relatively slightly more distal in the males of the white race, and slightly more proximal in the males of the negroes than in the females of either. There is no difference in the two races in the position of the insertion of the deltoid, similar to that found to be the case for the pectoralis major. The relative position of the deltoid insertion is also almost regularly unequal on both sides; more frequentl}^ the muscle is more proximally situated on the right side. In all the groups the averages of the position index of the deltoid are on the right — in part even considerably — smaller than those of the left side. A relationship between the strength of the deltoid muscle and its insertion position does not exist. The question as to what extent the positions of the insertions of the pectoralis major and the deltoid may change correspondingly is best answered by the following tabulation of the correlation coefficients with their probable errors for the two indices of position which have been previously used. White males + 0.52 ± 0.057, white females -f 0.37 ± 0.123, negro males + 0.29 ± 0.071, negro females + 0.70 ± 0.061. The coefficients, which are regularly positive, indicate that a shifting of one of the muscles is usually followed by a change to a greater or less extent of position of the other muscle in the same direction. This is very noticeable in female negroes and in male whites. In the material used the proximal point of measurement of the insertion of the deltoid was found above the distal point of measurement of the pectoralis major muscle insertion in one hundred and eighty-six cases; sixteen times t'le points referred to were at the same height and in only eight cases was the first point found below the latter.

The most proximal region of insertion of the deltoid is much more variable than the most distal. In order to free the index

168

ADOLF H. SCHULTZ

of position, which has just been discussed and which uses the mesLU value depending on the two terminal points of the insertion, from the great variability of the upper point it was found necessary to calculate a second position index for the deltoid, employing only the most distal point of insertion. This new index gives information as to how far down the deltoid extends upon the humerus. The formula for this index, using the measurements of figure 1, reads as follows:

measurement 5 measurement 1

X 100

The averages and conditions of variability of the index of the relative position of the most distal point of attachment of the deltoid are given in table 7. The entire variation reaching from 44.8 to 57.5 comprises 25 per cent of the mean obtained fromthe end values just cited; it is therefore relatively much smaller than the variation of the preceding index, which employed the middle point of insertion. The variation coefficients in table 7 lie in all the groups below those in table 6 and should be considered as relatively small. The position of the most distal point

TABLE

Averages, standard deviations, variation-coefficients, their probable errors and ranges of variation for the position index of the most distal point of insertion of the deltoid muscle

RACE

SEX

NUMBER

iSIDE

A/ ± £; (iW)

0- ± E (cr)

t) ± £; 00

MINIMUM

MAXIMUM

&

40

r.

50.13±0.21

1.98±0.15

3.95=^0.30

44.8

55.0

&

40

1.

50.81±0.21

1.96±0.15

3.86±0.29

47.9

57.5

Whites . .. . <

&

80

r. 1.

50.47±0.15

1.97±0.10

3.90±0 21

44.8

57.5

9

11

r.

49.88±0.35

1.74±0.25

3.49±0.50

45.6

52.5

9

11

1.

50.34±0.36

1.76±0.25

3.50±0.50

47.3

53.9

9

22

r. 1.

50.11±0.25

1.76±0.18

3.51±0.36

45.6

53.9

&

38

r.

49.59±0.16

1.50±0.12

3.02±0.23

46.2

52.8

cf

38

1.

50.18*0.15

1.41±0.11

2.81±0.22

46.5

52.9

Negroes ... ■

9

76 16

r. 1. r.

49.88±0.12 48.96±0.39

1.48±0.08 2.31±0.28

2.97*0.16 4.71±0.56

46.2 45.1

52.9 54,8

9

16

1.

49.52±0.37

2.21±0.27

4.46±0.53

45.0

54.1

^

9

32

r. 1.

49.24±0.27

2.27±0.19

4.61*0.39

45.0

54 8

PECTORALIS MAJOR AND DELTOID INSERTION

169

of the deltoid is accordingly the most constant of the points of muscle insertion which have been used, and can be located with considerable precision near the middle point of the humerus. Actually, this point lies slightly below the middle of the length of the humerus in whites, slightly above in negroes; a racial difference which is represented by the average difference of 0.73 of the averages of the index. In the female the most distal point of the deltoid is situated somewhat more proximal than in the male. It is also of interest to note, that the distal end point of the deltoid insertion, similarly to the middle point, is located on the average noticeably more distally on the left side than on the

TABLE 8

Absolute and relative numbers of individuals with symmetrical and asymmetrical

position of the most distal point of insertion of the deltoid and averages

of the individual differences of the position index

AVERAGE

RACE

SEX

THE SAME POSITION ON BOTH

POSITION ON THE RIGHT MORE

POSITION ON THE LEFT MORE

DIFFERENCE IF MORE DIST.'ULLY

cf

on the right

on the

left

Whites 1

= 0.0%

13 = 32.5%

27 = 67.5%

1.28

1.61

9

1 = 9.1%

5 = 45.4%

5 = 45.4%

1.28

2.28

Negroes <

9

2 = 5.2% = 0.0%

12 = 31.6% 6 = 37.5%

24 = 63.2% 10=62.5%

1.08 73

1.47 1.34

right. Table 8 gives a view of the absolute and relative number of individuals with equal and unequal indices of position for the most distal point of the deltoid insertion and also the average differences of the unequal indices. It shows that the point referred to occupies the same relative position on both sides in a total of only three cases; furthermore that the point was in a greater number of instances more distally situated on the left side, and that the differences in favor of the left always exceeded on the average those of the right. The greatest individual difference of the index appears in a white male with 6.4 in iavor of the left side.

The exact determination of the position of the insertion of the pectoralis major and deltoid muscles on the humerus shows,

170 ADOLF H. SCHULTZ

when briefly summarized, the possibiUties of variation, the more constant position of the deltoid insertion compared with the pectoraUs major, the equahty of the positions of the two muscle insertions in whites and negroes, the relatively higher attachment of the pectoralis major in females, and lastly the surprisingly common asymmetry of the insertion positions. The author has noticed that asymmetries of position of the insertions occurred as early as birth, although they are not as frequent nor as marked in the newborn as in adults.

In conclusion, the individual relative measurements and humerus lengths which form the basis of this paper are tabulated, and are arranged according to increasing lengths of the right humerus.

PECTORALIS MAJOR AND DELTOID INSERTION

171

White males

HUMERUS LENGTH

POSITION INDEX

FOR THE INSERTION

OF THE

PECTORALIS MAJOR

REL.\TIVE LENGTH

OF THE

INSERTION OF THE

PECTORALIS

MAJOR

POSITION INDEX

FOB THE

INSERTION OP THE

DELTOID

POSITION INDEX

FOR THE

MOST DISTAL POINT

OF INSERTION

OF THE DELTOID

Right

Left

Right

Left

Ri?ht

Left

Right

Left

Right

Left

283

283

31.3

31.8

16.6

19.8

41.7

41.9

49.8

50.9

286

286

28.5

27.8

13.6

11.5

42.3

41.4

52.4

51.7

289

294

28.4

29.6

15.2

12.2

44.8

43.0

55.0

53.1

296

303

27.2

28.5

20.6

14.2

42.6

41.7

47.6

47.9

299

291

27.9

28.4

18.4

15.5

42.3

40.7

50.2

52.2

299

298

29.9

30.2

23.1

20.8

41.8

41.8

50.5

51.0

299

301

27.4

29.2

17.4

16.6

37.6

42.0

47.2

50.2

300

300

29.0

26.0

16.7

18.7

39.3

39.0

48.3

50.0

302

294

29.0

26.0

12.3

13.9

42.9

42.7

50.7

51.4

302

296

28.5

26.9

15.9

15.9

42.7

41.0

51.3

48.3

302

311

29.5

30.2

15.9

12.2

41.1

42.1

49.7

51.4

304

303

25.0

27.9

18.4

17.5

37.3

43.1

48.4

50.8

306

313

27.8

28.9

15.7

16.0

37.4

39.3

49.6

49.8

307

307

28.7

28.7

20.8

15.6

36.5

39.7

50.5

51.5

311

310

29.7

27.0

17.0

16.5

40.4

40.3

50.2

48.7

314

312

30.1

29.8

9.2

17.3

38.5

39.6

51.3

52.6

315

311

26.8

27.5

15.0

12 5

40.3

39.2

49.8

48.9

315

315

27.5

30.6

17.5

20.0

43.0

45.6

51.1

57.5

315

315

26.7

27.5

19.0

18.7

39.7

41.6

51.1

50.2

317

310

28.2

27.7

19.2

16.8

38.6

43.2

51.7

51.6

319

318

27.0

28.9

16.9

14.5

40.6

41.2

50.8

50.3

319

319

28.1

30.3

17.9

17.2

40.4

43.9

50.2

52.0

320

315

30.2

31.1

16.6

14.0

43.1

43.3

53.7

52.4

321

320

25.5

25.3

19.3

20.0

38.3

37.5

47.7

48.4

321

326

28.8

cO.5

14.6

16.9

39.6

41.9

52.6

54.0

323

318

27.9

27.5

18.0

16.0

40.6

39.6

49.8

48.1

323

327

24.3

27.1

17

19.3

38.5

40.4

47.7

48.3

324

320

29.6

29.4

19.1

16.9

42.1

39.5

53.1

51.3

328

329

30.5

30.1

15.2

18.5

42.7

43.0

50.9

52.3

329

327

28.9

27.7

15.2

16.2

40.3

40.7

48.9

50.5

332

343

27.1

27.7

15.7

16.9

38.1

40 1

46.4

48.1

333

333

30.0

27.2

16.8

13.5

39.6

40.2

50.5

51.4

334

327

29.0

28.9

14.4

13.8

40.9

41.3

49.1

48.9

334

336

29.6

28.6

17.4

19.0

40.4

42.1

51.2

51.8

334

336

29.9

30.8

19.2

17.0

43.0

45.2

51.5

54.2

334

346

31.1

27.5

15.6

15.6

43.6

39.6

51.8

49.7

335

332

29.1

27.4

15.8

18.7

38.9

39.8

44.8

49.1

335

335

26.9

27.6

16.1

18.2

39.3

39.1

49.3

49.6

346

352

27.2

28.6

17.9

13.9

39.9

41.9

51.2

52.6

347

347

27.1

27.5

17.3

14.7

37.2

37.8

47.8

49.6

172

ADOLF H. SCHULTZ

White females

HUMERUS LENGTH

POSITION INDEX FOR THE INSERTION

OF THE PECTORALIS MAJOR

RELATIVE LENGTH

OF THE

INSERTION OF THE

PECTOR.'ILIS

MAJOR

POSITION INDEX

FOR THE

INSERTION OF THE

DELTOID

POSITION INDEX

FOR THE

MOST DISTAL POINT

OF INSERTION

OF THE DELTOID

Right

Left

Right

Left

Right

Left

Right

Left

Bight

Left

269

267

26.2

28.8

18.2

15.7

42.2

42.9

49.8

49.4

279

278

26.9

28.5

13.6

16.5

36.2

41.7

49.1

50.4

281

280

27.0

27.7

17.1

14.6

37.7

37.7

49.5

49.6

284

290

28.3

25.9

15.8

17.2

42.3

41.7

51.4

51.4

290

281

24.1

21.5

14.5

17.4

38.1

38.8

50.0

47.3

299

288

27.8

29.5

18.1

21.5

42.5

42.2

51.5

51.4

299

303

21.9

21.3

17.1

19.5

39.6

39.9

48.8

49.2

301

298

27.1

27.3

20 3

17.8

40.5

41.8

52.5

52.0

306

290

27.1

24.0

19.6

15.5

39.2

36.4

51

48.3

307

. 295

26.5

27.5

16.0

12.9

34.0

40.7

45.6

50.8

309

295

27.2

27.9

16.2

13.2

40.6

42.9

49.5

53.9

Negro males

290

283

26.6

26.3

17.2

18.7

41.4

42.0

48.3

48.4

298

298

29.2

31.0

14.8

15.8

40.0

42.1

47.0

49.7

301

292

27.7

28.1

18.3

17.1

40.5

41.4

48.5

49.7

303

301

29.5

26.9

14.2

12.6

40.3

40.7

49.8

49.8

307

310

• 27.9

28.0

16.6

17.1

38.6

36.6

49.8

50,0

308

303

27.9

28.5

16.2

16.8

42 2

42.7

51.0

50.8

308

307

26.5

25.7

18.5

20.2

37.0

37.1

49.7

51.1

312

306

27.9

28.9

17.3

15.4

39 1

40.5

50

50

312

307

30.6

32.6

9.3

17.6

43.9

41.9

50.0

51.1

313

313

29.6

29.6

22.7

17.6

42.5

41.7

51.4

49.5

318

316

27.7

28.5

13 8

18.4

38 2

41.9

51.3

51

320

314

28 9

27.2

9.1

16.9

41.4

40.4

51.0

50.6

320

319

27.3

25.1

21.6

19.4

39 8

37.1

50 6

51 1

322

316

26.1

25.8

18.0

15.5

43 3

42.9

51.6

52.9

322

316

26.9

26.9

14.6

13.9

40.8

42.1

49.7

50.3

322

322

26 6

29.0

18.9

15.2

38.8

41.9

50

48.5

322

322

28.9

29.5

14 .'3

19.9

40.5

41.6

48.1

49.7

323

316

27.2

26.4

21.7

15.5

35.6

36.2

49 5

48.4

323

318

28.9

30.0

19.5

17.3

40.7

42.5

48.9

51.6

323

323

29.7

29.3

16.7

14.5

41.8

41.6

48 3

50.8

325

328

26.3

29.0

8.9

11.0

34

37.0

46.2

50.9

328

305

29.7

28.5

8.8

10.5

39.3

39.5

48.5

51.5

328

327

29.3

27.7

19.5

18.0

44 7

40.5

49.7

49.8

329

329

28.7

28.0

16.7

14

40 6

39.1

49.2

46.5

330

330

27.6

27.4

14 5

16.7

37.3

40 6

50

51.8

331

324

28.1

26.7

15.7

13.3

38.7

37.2

48.3

48.8

PECTORALIS MAJOR AND DELTOID INSERTION

173

Negro

males—

-Continued

HUMEKUS LBNGTH

POSITION INDEX

FOR THE INSERTION

OF THE

PECTORALIS MAJOR

RELATIVE LENGTH

OP THE

INSERTION OF THE

PECTORALIS

M.UOR

POSITION INDEX

FOR THE

INSERTION OF THE

DELTOID

POSITION INDEX

fOR THE

MOST DIST.VL POINT

OF INSERTION

TO THE DELTOID

Right

Left

Right

Left

Right

Left

Right

Left

Right

Left

332

333

26.5

26.9

16.9

15.3

40.2

40.7

49.4

51.7

337

332

35.2

29.2

11.6

15.7

40.8

40.2

48.4

48.8

338

339

30.5

26.8

20.7

17.7

40.2

37.9

48.8

47.8

339

347

29.1

30.3

20.9

17.9

43.8

42.7

52.8

51.0

342

342

27.2

28.2

16.4

16.7

43.9

44.6

51.8

52.6

342

344

29.5

27.2

11.7

14.8

39.3

39.8

47.1

48.3

345

352

28.0

29.1

14.8

17.3

41.6

41.2

48.4

48.6

349

350

28.7

26.3

16.0

17.7

39.7

40.9

49.0

50.0

350

348

26.9

27.0

16.0

19.0

42.4

41.7

51.1

49.7

355

352

24.4

25.9

17.2

17.0

40.4

38.8

47.9

49.7

360

345

27.8

28.7

14.4

15.1

42.1

40.3

52.8

52.2

367

365

29.3

27.4

18.8

16.4

39.8

42.1

50.4

52.1

Negro females

266

260

27.3

25.6

13.2

15.8

41.2

41.7

48.5

50.0

272

269

27.0

26.8

15.8

17.1

42.6

42.2

50.0

50.6

280

271

28.7

27.3

14.6

14.0

40.4

42.1

47.9

50.9

283

279

30.9

30.3

16.6

20.4

46.5

45.0

54.8

54.1

285

285

27.4

28.4

14.7

17.5

41.9

42.3

50.2

49.5

286

286

26.7

26.2

15.0

14.7

37.4

39.3

45.1

45.5

290

290

28.3

27.9

13.1

16.6

41.7

41.7

51.4

51.0

297

297

27.4

26.8

21.9

19.9

41.8

43.8

49.2

50.8

301

296

24.9

25.8

18.6

18.6

38.0

38.0

48.8

48.6

301

301

23.1

22.3

12.3

12.0

38.7

38.7

47.2

47.8

302

302

23.7

23.5

16.9

17.9

37.1

37.4

48.3

49.0

303

298

26.9

26.8

15.5

15.4

41.7

42.4

49.8

50.3

308

302

25.3

25

19.5

19.5

34.3

36.1

46.1

45

309

307

25.6

25.9

16.2

15.3

43.0

40.9

49.5

48.2

309

309

27.7

27.5

16.5

19.4

43.4

44.8

50.8

52.1

321

312

28.2

27.2

14.0

16.0

40.5

41.3

45.8

49.0