Paper - The development of the vena cava inferior

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Lewis FT. The development of the vena cava inferior. (1902) Amer. J Anat. 1(3): 229-244.

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This 1902 paper describes rabbit inferior vena cava development.

Also by this author: Lewis FT. On the cervical veins and lymphatics in four human embryos, with an interpretation of anomalies on the subclavian and jugular veins in the adult. (1909)

See also later paper: McClure CFW. and Butler EG. The development of the vena cava inferior in man. (1925) Amer. J Anat. 35(3): 331-383.


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The Development of the Vena Cava Inferior

Frederick Thomas Lewis
Frederick Thomas Lewis (1875-1951)

By

Frederic T. Lewis, A. M., M. D.

From the Embryological Laboratory, Harvard Medical School.


with 11 Text Figures AND Two Double Color Plates.

In a course of lectures on the problems of embryology, Prof. C. S. Minot demonstrated that the current descriptions of the embryonic vena cava inferior are inadequate, if not actually erroneous. Under his direction, the rabbit embryos of the Harvard Embryological Collection have been examined in order to revise Hochstetter’s work, already once repeated by Zumstein. The results of this third investigation of the rabbit’s cava inferior justify a new description of the vein, illustrated by lithographs, a gift from the Elizabeth Thompson Science Fund.


In rabbit embryos of about ten days, the abdominal veins are absolutely symmetrical. On either side of the intestinal, canal runs an omphalo-mesenteric vein, which unites with the umbilical vein from the somatopleure of the corresponding side just before joining the duct of Cuvier. (See Hochstetter, 93, p. 546, Fig. 1.) For reasons Which have not been explained this system becomes asymmetrical, and normally is predominant on the right side. On the 12th day the venous orifice of the heart is on the right; the right umbilical and right omphalomesenteric veins are larger than the left,‘ and the vessels on the left side are forming a new channel, the ductus venosus Arantii, Which conveys their blood directly across the liver to the right auricle.


The liver develops from the ventral Wall of the intestine by sending its tubules into, and thus subdividing the omphalo-mesenteric veins. This condition was noted by Hochstetter (93, p. 5-16) and others, and has since been fully described by Minot (00, pp. 197-202), who named the small venous subdivisions “sinusoids.”

As the venous channels become predominant on the right side, the liver consequently develops more rapidly there and becomes a right sided organ.


1 Although the right umbilical vein, in the early part of the 12th day, is larger than the left, and may be described as “colossal,” the left umbilical vein is the one which persists throughout embryonic life.


Veins and liver combine to push the stomach toward the Fig. 1, a frontal section of a 5 mm. rabbit, shows clearly the barrier formed by the veins and liver, with the consequent forcing of the stomach to the left.


Fig. 1. Rabbit embryo of 5 mm , 12 days. Series :05, section140. x 25 right enlarges.


of a 5 mm. rabbit. The bulging of the stomach toward the left has caused it to present on that side a smooth rounded surface, but on the right it is irregularly indented and the .mesenchymal fold referred to, C. M., becomes accentuated. This fold is destined to contain the inferior cava, and has been called the “mesenteric bridge ” by Goette (75, p. 818), the “pliea venae cavze” by Ravn (89, p. 140), and the “ caval mesentery” by Hochstetter (93, p. 564). In later stages the elongated gastric mesentery runs sharply to the left, and from its right side, where it joins the body wall, springs this caval mesentery. As a whole the mes It may confidently be assumed that had the originally symmetrical veins persisted on the left side, stomach, liver, and later the vena cava would shift their position, resulting in


The position of the vena Cava inferior as yet unformed, has been determined by the asymmetrical development of the umbilical and omphalo—mesenteric veins. In the early rabbit stages, there springs from the root of the dorsal mesentery a pair of mesenchymal lobes, one on either Traced anteriorly they pass into the mesenchynial anlages of the lungs, the alm pulmonales of Ravn (89, p. 139), which precede the epithelial outpocketings from the oesophagus. are at first quite symmetrical, but with the displacement of the stomach, the fold on the left is obliterated and that on the

These wings

Fig. 2 is a. cross-section

FIG. 2. 12 days. x 25. Rabbit embryo of 5 mm., Series 104, section 317.

entery is now V-shaped, the left arm or mesogastrium going to the stomach, and the right arm or caval mesentery ending freely in the abdominal cavity. The fate of the caval mesentery is briefly this. The part most cephalad is invaded by the right lung, of which it forms the lobus inferior medialis of Krause (Ravn, 89, p. 144). Below the diaphragm it meets and unites with the liver. Hepatic tubules grow into it and it becomes a part of the liver. Thus it at once connects the liver with the right dorsal wall and causes the hepatic sinusoids to come quite close to the posterior cardinal vein. Still further caudad there is a place where the caval mesentery has not united with the liver, but is free. letween liver and mesentery there is left a long slender passage, the foramen of Winslow.


FIGS. 3-6. Rabbit embryo of 8.8 mm., 13 days. Series 465, sections 256, 246, 217, 215, respectively. x 20.


These relations are illustrated by Figs. 3-6, transverse sections of an 8.8 mm. rabbit. In Fig. 5 the foramen of Winslow, F. W., bounded by caval mesentery and by liver, is seen leading to the lesser omental cavity. Fig. 4 shows the caval mesentery uniting with the liver above the foramen of Winslow; a notch, N, marks the limit of the original hepatic lobe, but the tubules now fill the caval mesentery. At a higher level, as in Fig. 3, the notch becomes obliterated. Below the foramen of Winslow the caval mesentery again unites with the liver, as shown in Fig. 6, but is here rather a “ portal mesentery,” for it contains the portal vein. Since the relations of this portal mesentery and its connection with the ventral border of the stomach have nothing to do with the cava inferior, its further consideration is reserved for a subsequent paper. The foregoing description has shown how the path for the vena cava is laid out, and why the vein is to be unilateral. We may now consider the development of the vessel itself.


In the embryos of 5 mm. the aorta passes toward the tail as a median unpaired vessel lying dorsal to the root of the mesentery and ventral to the spinal cord. On either side of it runs a posterior cardinal vein, as shown in Fig. 2. The Wolffian bodies are found in the caudad part of the abdomen, ventra.l to the cardinal veins. The tributaries of the posterior cardinals are the intersegmental veins arising regularly between the dorsal ganglia, and a number of irregularly placed small vessels Which come from the mesenchyma in front of the aorta, and from that around the Wolfiian tubules. These branches are obscure in the early stages but in an embryo of 6.6 mm. they are plainly seen. Fig. 7 illustrates their arrangement. A vessel is shown passing from the mesentery into the left posterior cardinal vein. The Wolffian body is represented by a knot of coiled tubules. The tributary of the cardinal passes along its median surface, after receiving a branch from its ventral border. Other cardinal branches curve over its dorsal side so that the Wolffian body becomes nearly surrounded by veins. The later intercrescence of Wolifian tubules and cardinal veins has been carefully described by Minot in his paper on sinusoidal circulation (oo, pp. 193197). It is important that the cardinal tributaries may anastomose with one another, and, in front of the aorta, with those of the opposite side. These anastomoses are found in embryos of 7.5 mm.


Beginning with an embryo of this length four stages in the development of the veins have been illustrated by reconstruction after the method of His. The drawings are similarly enlarged and arranged in Plates I and II. Each pair of figures represents a single embryo, split in the median plane and laid open, the left half of the embryo lying on the right-hand page, and vice versa. All the blood-vessels involved have been drawn except the median aorta and its median (mesenteric and gastric) branches. Every drawing shows two sets of arteries: lst, a regularly arranged series of intersegmental arteries, A. I., and 2nd, the irregularly disposed arteries running laterally from aorta to the glomeruli of the Wolffian body. These may be named the mesonephric arteries, A. M.: their position in relation to the veins makes them a most important 1an'dmark. The umbilical arteries, A. U., are also indicated; All the arteries are shown as cut across at the position where they leave the aorta.


FIG. 7. Rabbit embryo of 6.6 mm., 12 days, 12 hours. Series 460, section 117. x 45. This section should have been reversed to be in the conventional position. The right side ishere drawn at the right of the observer.



Figs. 1 and 2, Plate_I, picture the condition already described. In this 7.5 mm. embryo the posterior cardinal veins, V. C., pass cephalad to join the anterior cardinals, and then to turn back at a sharp angle and enter the heart. Ventral to the posterior cardinal vein is seen the line of mesonephric arteries, and ventral to these is an anastomosis of cardinal tributaries. This anastomosis forms a new vessel coming from the cardinal in the caudad region, emptying again into the cardinal anteriorly, and connected with the cardinal all along the line by cross branches running between the mesonephric arteries. This new vessel I would designate as the subcardinal vein, Vena subcardinalis. The bilateral symmetry of the veins at this stage is complete. The small vessels from the mesentery, and mesenchyma ventral to the aorta are represented in the drawings, one of them being labelled V. m., and two points of anastomosis with the veins of the opposite side are designated by the letters V. In. X. Thus the subcardina.l veins are connected with one another by vessels of small calibre.


In Fig. 1, Plate I, a portion of the liver has been outlined. The portal vein, V. 0. M., is shown cut across in the median plane. It passes behind the intestine toward the right and forward through the liver connecting with the ductus venosus, D. V. A., and ending in a vessel known as the vena hepatica communis. This comprehensive name was applied by Hochstetter (93, p. 552) to that trunk passing from the liver to the heart, and formed by the union of hepatic, umbilical, and omphalo—mesenteric veins, to which the inferior vena cava is later added. In the figure a black, partly dotted line marks the limit of the dorsal hepatic lobe, which is filled with sinusoids. Some of these channels, V. c. m., have extended over into the caval mesentery, into which the hepatic cylinders are to follow them.


A large stream of blood traverses the liver through the broad venous spaces unimpeded, whereas the current through the cardinal veins is clogged by the Wolffian tubules. The development of the posterior limbs demands a freer passage, and the formation of the subcardinals may be regarded as the attempt of the cardinal veins to become disentangled from the Wolfiian body. Probably the recurrent bend of the duct of the Cuvier is another obstruction to the posterior cardinal system. At all events the right subcardinal and the hepatic sinusoids approach one another and unite, thus forming a new access to the heart. All the component parts of the adult vena cava inferior have now become connected. The new passage is so favorable that it enlarges rapidly. On the left side, the subcardinal can make no connection with the liver, since the stomach has cut off any approach to that organ. There has been no reversal of blood currents on either side, but blood from the lower left area crosses to the right through the anastomoses between the subcardinals. The cardinal system has been tapped by the hepatic.

Figs. 3 and 4, Pl. I, represent a rabbit of 8.8 mm. The subcardinal veins, V. Sc., are now large, and that on the right has connected with the vena hepatica communis. See also the cross section, Fig. 4, p. 231.

It extends for a short distance beyond this connection, as shown clearly in the cross section", Fig. 3. Below the superior mesenteric artery five anastomoses between the subcardinals could be followed, the first of which is lettered X. Fig. 6 of the cross sections passes through the anastomosis X. Just below the superior mesenteric artery a cross connection between subcardinal and- cardinal becomes very large and marks an important subdivision of both vessels into superior and inferior parts. The superior portion of the subcardinal enlarges, its inferior division diminishes, and correspondingly the inferior section of the cardinal enlarges, its superior part becomes small. Thus the inferior part of the cardinal and superior part of the subcardinal are both large, and, by the obliteration of the kink made by the anastomosis between them, become a single straight channel. On the right side they persist as a part of the adult vena cava inferior.


FIG. 8. Rabbit embryo of 11 mm., 14 days. x 28. This series is not one of the Harvard Collection.


As the superior part of the cardinal vein shrinks in calibre, it loses its continuity as a venous trunk, although its disjoined sections are still connected by the sinusoids of the Wolffian body. Fig. 3, P1. I, shows the anterior part of the cardinal, V. C. a., separated from the posterior division, V. C. 1).‘ On the left side, however, the vessel is still continuous from the pelvis to the duct of Cuvier.

The third reconstruction is from_an 11 mm. rabbit, Figs. 5 and 6, P1. II. The cardinal veins are now both subdivided as just described.


A notable change is in the decreasing importance of the inferior part of the subcardinal veins. Only two of its cross connections remain, of which one, X, has become very large. A cross section, Fig. 8, of this embryo, taken a short distance above this region shows the symmetrical arrangement of the vessels, and the large size of the subcardinals on both sides. The subcardinals lie at the ventral corner of the hilus of the Wolflian body from which they receive tributaries, just as do the cardinals at the dorsal corner. The veins are separated from one another by the mesonephric arteries, a pair of which is seen in the section. At the upper end of the veins, on either side, cardinal and subcardinal anastomose in condensed mesenchyma probably connected with the suprarenal anlage.


In the rabbit of 8.8 mm., the kidney on either side was situated in front of the iliac artery, as described by Hochstetter, and beautifully drawn in his Fig. 18 of Pl. XXII (93). As it develops, it drops back over the artery and falls between the cardinal vein and the aorta, or even directly upon the cardinal. It may split the cardinal vein so as to form a loop, as figured by Hochstetter, but I have not seen any complete loop. In Fig. 6, Pl. II, the position of the kidney is indicated by R. A portion of the cardinal vein receiving two intersegmental veins has been separated from the main trunk and pushed dorsad. On the right side of the same embryo, Fig. 5, Pl. II, the vein was not divided, but the kidney had distorted the course of two intersegmental veins. The main cardinal stem bends rather sharply outward around the obstructing kidney and so comes to lie on the outer side of the lower end of the Wolflian body.‘ The ureter is now on the median side of this large trunk. From the shattered inner pieces of the cardinal Vein, or from new off shoots of the main stem, a venous connection forms on the median side of the ureter. Such a loop is seen in Fig. 5, the letter U marking the passage for the ureter. This new median arm of the loop is in line with the main vessel; it enlarges and becomes a part of the cardinal trunk. The vein has again become straight, but the ureter has been transferred from its inner to its outer side. The outer arm of the loop becomes smaller, and its caudad portion is divided into many sinusoids. It then appears as a large branch of the cardinal vein, entering it from the dorsal border of the Wolffian body. Thus it forms the Urnierenvene of Hochstetter (93, p. 583). The ureter remains in the loop and passes, therefore, ventral to the iliac artery, external to the cardinal vein, and dorsal to the Urnierenvene. My examination of these renal relations confirms the observations of Hochstetter (88 and 93) in almost every particular. ' Figs. 7 and 8, Pl. II, from a rabbit of 14.5 mm., show at Y the new cross connection between the cardinal veins in their pelvic portion. The kidney lies behind the Wolffian body, the hilus of which it compresses, as shown in Fig. 9. The renal vein is a branch of the cardinal at the level of the large anastomosis of that vessel with the subcardinal. In the pelvic part of it course the cardinal receives the vena lumbalis


1 In pig embryos of 12.0 mm. the main cardinal vessel passes to the outer side of ‘the caudal end of the Wolfiian body uninfluenced by the renal anlage.



FIG. 9. Rabbit embryo of 14.5 mm., 14 days, 18 hours (17). Series 143, section 827. x 30. '

transversa posterior. This is a large irregular vessel in the body wall, connected with one or two intersegmental veins, and suggesting the trunk which was split off by the kidney shown in Fig. 4, Pl. I. The intersegmental veins were easily followed in younger and in older cmbryos, but at this stage their connections with the cardinal are very obscure. This may be due to distortion caused by the migration of the renal artery. The superior section of the cardinal receives a large transverse lumbar vein, two intersegmental veins, and small vessels from mesenchyma in -the suprarenal region. On the right side a con— siderable area fuses with the subcardinal and is incorporated in the vena cava. The mesonephric arteries become obliterated. In a rabbit of 21 mm. a single one of them remained on either side above the anastomosis X. The relations of the vessels in this region are shown in Fig. 9, the section on the right side passing through the fused subcardinal and cardinal. The inferior sections of the subcardinal veins no longer receive branches from the Wolflian bodies, but appear as large spaces in the mesentery, conspicuous. ly empty of corpuscles, though the adjoining veins are -full of them. The mesenchyma in _ _ _, front of the aorta below G./\. . the anastomosis X is perFm. 10. Rabbit embryo of 14.5 mm., 14 days, 18 hours ('2). Hleatefl 13)’


Series143. section 857. X 45. The vessels shaded with - . lines contain corpuscles; the others are empty. 3-S S110W11 111 F1g- 10~ Mere strands of mesenchyma separate them from one another and the adjoining veins. Their fate is unknown, but they recall the description by Sala, 00, of the anlages of lymphatic hearts in the chick. They pass into slender vessels, empty of corpuscles, which extend some distance cephalad from the anastomosis X. They appear in the position previously occupied by the lower part of the subcardinal, and at the time when those vessels disappear. Therefore they may be subcardinal derivatives.


On the left side, the superior part of the subcardinal vein begins as a considerable branch from the Wolflian body, uniting with another from the suprarenal area. It receives vessels from both structures along its course. The size of this part of the left subcardinal 319,11, Reconstruction 110,13,-abin a 21 mm. rabbit is shown in.Fig. 11, }’6’4t_°§‘§§_y° °f 2’m'”"” days‘ “we” drawn with the same magnification as

Fig. 8, Pl. II. The suprarenal body is found between the cardinal and

subcardinal veins which lie very close to it, the cardinal at the dorsal surface and the subcardinal ventrally. The suprarenal body extends far beyond the traceable branches of the subcardinal vein. In a 29 mm. rabbit the relations were similar. The very small and short subcardinal vein came from the suprarenal body, from which possibly the cardinal also received some small branches. They could not definitely be followed. In Hochstetter’s description the left subcardinal is named the left suprarenal vein from thefirst. It is quite probable that the subcardinal may become the adult suprarenal, though I shall not consider it an established fact until still older embryos have been examined. Kollmann (98, p. 477) writes that it becomes “ bis auf unbedeutende Gefasse rudimentar.”


The posterior section of the left cardinal vein becomes divided either above the Urnierenvene, or below it, or below the transverse lumbar vein. Hochstetter (93, pp. 585-586), gives figures of the three resulting conditions in the adult. In the 21 mm. rabbit the division had occurred below the transverse lumbar vein, as is usual; the 29 mm. specimen had divided above that vein. The Urnierenvene becomes the spermatic vein of the adult; and the remaining part of the posterior section of the left cardinal, into which it flows, is called the ascending lumbar vein. This lumbar vein terminates in the renal vein, the old anastomosis extending from the cardinal through the subcardinal to the opposite side. N-o later changes of importance occur in these veins.


The present inaccurate text-book accounts of the development of the vena cava inferior have justified the reiteration of many well established observations. Schafer, in Quain’s Anatomy, illustrates a very brief description by diagrams from Kiilliker. These figures, published’ in K6llik.er’s Grundriss in 1884 (p. 404, Fig. 276) among other errors represent the cava as a vessel separate from the cardinals to the common iliacs. Schultze in 1897 (p. 406, Fig. 357) replaced these diagrams by a modification of those of Hertwig, whose faulty figures have enjoyed great popularity. (See Hertwig, oo, p. 350, Fig. 315.) Kollmann (98, p. 470, Fig. 292 A) gives the only accurate diagram of the early vena cava inferior which I have seen.‘ His figure agrees with the description by Hochstetter of the vein on the left side, symmetrical with the vena cava on the right, but Kollmann is misled in stating that the vena cava “ setzt sick in Verbindung ” with the cardinal veins. In this he follows Hocl1stetter’s earlier description (93, p. 569).

“ The posterior vena cava passes over from the liver into the caudal continuation of the caval mesentery (into which small branches from the hepatic venous network also enter), and thence may be followed, in the youngest stage in which I saw the cava. a short distance further 240 The Development of the Vena Cava Inferior

toward the median side of the right Wolffian body. In the next older stage the posterior vena cava passes through the caval mesentery and then puts itself on the median side of the Wolfiian body, along which it may be followed for a considerable distance beyond the place of origin of the superior mesenteric artery. Moreover, there is a vein on the left side quite similar in position to the caval trunk on the right, which extends as far caudad as the latter, and begins at the level at which the vena cava meets the right Wolfiian body. It is joined to the vessel on the right by two or three weak cross connections. These roots of the posterior cava are united with the cardinal vein only by very weak vessels which should be reckoned as capillaries.”


This description has been taken to mean that the vena cava inferior developed downward from the liver, that the symmetrical vein on the left was a branch of it, and that this system acquired its connection with the cardinals. Although his language is somewhat vague, this, I believe, is what Hochstetter meant. On p. 602 he describes a human embryo in which the symmetrical veins (subcardinals) were apparently separate from one another. In a significant foot note Hochstetter says that cross connections may have been present but invisible because empty, “ otherwise the left vessel must be regarded as an independent anlage.” Grosser (01, p. 362) describes a similar condition in bats. “ The right cardinal vein stands already in broad connection with the posterior veua cava which continues beyond this anastomosis along the median side of the Wolfiian body. A left H ohlvenemmlage symmetrical with the right is present, and joined to the right by one (or two?) almost capillary channels. Moreover, this vessel is united with the left posterior cardinal by slender vessels, but this union plays no great role.” Nevertheless, I consider these connections to be important and primary, the longitudinal anastomosis forming next, and, finally, on the right side, the union with the liver which has invaded the caval mesentery. Zumstein (98, pp. 311-312) gives a more accurate description than Hochstetter. In the mole of 3 mm. he found “ on both sides, median and ventral to the cardinals, small venous passages which united with the cardinal veins. Those on the right could be followed to the hepatic vessels. This condition differs from that of younger stages in possessing a clear connection between the right cardinal vein and the hepatic vessels. In the liver itself there is no clear passage which can be designated as the vena cava inferior.” Zumstein did not appreciate the importance of these observa tions, which are illustrated by crude figures. He concluded his paper by disputing with I-Iochstetter regarding the spermatic veins and was told in reply (Hochstetter, 98, p. 517) that he had “brought to light no new fact regarding the development of the rabbit’s inferior cava.”


That the plan of development decribed for the rabbit is of wide application is probable. Grosser has found it in bats, Zumstein in the mole, Hochstetter and Kollmann have indicated it in human embryos. I'have found a similar arrangement in pigs, and note that the reconstruction of the pig’s veins by Minot (98, Pl. I, Fig. 5) is incomplete. Dr. Minot has pointed ou.t to me in the original reconstruction several sectioned areas in the veins, omitted in the figure. A more complete drawing of these vessels is to appear in his “ Text-book of Embryology.”


Finally a paragraph concerning nomenclature! The vena cava inferior is a compound vessel belonging to the adult rather than to the embryo. It consists of a part of the heart, then in turn, parts of the vena hepatica communis, dilated sinusoids of the liver, part of the right subcardinal vein, and a section of the right posterior cardinal vein. It has been the custom of certain embryologists to give the name of the whole to one of its parts, namely to the subcardinal portion, and even to charge with ignorance those who called other sections of the adult vessel the vena cava. I agree with Dwight (01, p. 29) that it is quite accurate to speak of the “cava below the diaphragm” or above the diaphragm.

Summary

The persistence of the right umbilical and right omphalo-mesenteric veins causes the stomach to be pushed to the left side and the liver to become predominant on the right.


This displacement of the stomach causes the left mesenteric fold, continuous with the ala pulmonalis, to disappear; but the fold on the right, the caval mesentery, enlarges. It fuses with the liver, becomes invaded by hepatic tubules and made a part of the right dorsal hepatic lobe. Thus it causes the hepatic vessels to lie near the posterior cardinal vein.


Small vessels from the mesentery pass into the cardinals. They anastomose in front of the aorta with the vessels of the other side. They form a longitudinal anastomosis parallel with the cardinal vein, with which it is connected by numerous short veins, and from which it is separated by a line of mesonephric arteries. This longitudinal vessel connected with the cardinal vein at both ends, and bilaterally symmetrical in its early stages is the subcardinal vein.


The cross connections between the subcardinal veins give place to a single large cross anastomosis caudad to the origin of the superior mesenteric artery. Above this anastomosis the right subcardinal connects with the liver and rapidly enlarges; the left subcardinal becomes very small—Hochstetter says that it forms the left suprarenal of the adult. Below the anastomosis the subcardinals cease to exist as veins; they may persist as lymphatic spaces.

The vena cava inferior is a compound vessel composed of parts of the heart, the vena hepatica connnunis, the hepatic sinusoids, the upper part of the right subcardinal, and the lower part of the right cardinal vein.


Literature Cited

DWIGHT, THOMAS, 01, — What constitutes the inferior vena cava? Anat. Anz., Vol. XIX, pp. 29-30.

GOETTE, ALEXANDER, 75, — Die Entwickelungsgeschichte der Unke. Leipzig. pp. 1-196.

GR0SSER, OTTO, 01.— Zur Anat. und Entw. des Gefiisssystemes der Chiropteren. Anat. 1-lcfte, Abt. 1, Vol. XVII, pp. 203-424.

HERTWIG, OSCAR, 00. — Die Elemente der Entwicklungslehre des Menschen. Jena. pp. 1-406.

HOCHSTETTER, FERDINAND, 88. — Ueber den Einfluss der Entwickelung der bleibenden Nieren auf die Lage des Urmerenabschnittes der hinteren Cardinalvenen. Anat. Anz.. Vol. III, 1313. 938-940.

HOCHSTETTER, FERDINAND, 93. — Beitr’cige zur Entwicklungsgeschicte des Venensyst_ems der Amnioten. III Sfiiuger. Morph. Jahrb., Vol. XX, pp. 543-648.

HOCHSTETTER, FERDINAND, 98, — Bemerk11ngen zu Zumsteins Arbeit. Anat. Hefte, Abt. 1, Vol. X, pp. 511-517.

KOLLIKER, ALBERT, 34, — Grundriss der Entwickelungsgeschichte des Menschen. Leipzig. 2nd ed., pp. 1-454.

KOLLMANN, J. 95, — Lehrbuch der Entwickelungsgeschichte des Menschen. Jena. pp. 1-658.

MINOT, CHARLES S., 98, — On the veins of the Wolflian body in the pig. Proc. Bost. Soc. of Nat. Hist, Vol. XXVIII, pp. 265-274.

MINOT, CHARLES S., 00, —0n a hitherto unrecognized form of blood circulation Without capillaries in the organs of Vertebrata. Proc. Bost. Soc. of. Nat. Hist., vol. XXIX, pp. 185-215.

RAVN, EDVARD, 39. - Ueber die Bildung der Scheidewand zwischen Brustund Bauchhifihle i11 Stiugethierembryonen. Arch. f. Anat. u. Entw. 1889, pp. 123-154.

SALA, LUIGI. 00 — Suno svilluppo dei cuori linfatici e dei dotti toracici nell’ embrione di pollo. Ric..fatte nel Lab. di Anat. norm. (1. R. Univ. di Roma, Vol. VII, pp. 263-296.

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Explanation of Plates

Plate I

LewisFT1902 plate01-fig1.jpgLewisFT1902 plate01-fig2.jpg

Figs. 1 and 2. Reconstruction from a. rabbit embryo of 7.5 mm., 12 days, 12 hours. Series 454. X 25.

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Figs. 3 and 4. Reconstruction from a rabbit embryo of 8.8 mm., 13 days. Series 465. X 25.

Plate II

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Figs. 5 and 6. Reconstruction from a rabbit embryo of 11.0 mm., 14 days. This series is not one of the Harvard collection. X 25.

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Figs. 7 and 8. Reconstruction from a rabbit embryo of 14.5 mm., 14 days, 18 hours (?). Series 143. X 25.

Lettering of Plates and Figures

The first and last of the spinal ganglia represented in the plates are numbered, the first cervical ganglion being counted 1.

Lettering of Plates and Figures  

A. I., intersegmental artery. In each plate only the first and last have been lettered.

A. M., mesonephric artery. In each plate only one of several has been lettered.

A. M. S., superior mesenteric artery.

A0., aorta

A. R., renal artery.

A. U., umbilical artery.

0. M., caval mesentery.

D. C., duct of Cuvier.

D. V. A., ductus venosus Arantii.

F. W., foramen of Winslow.

G. A., genital anlage.

Ht., heart.

Ki, kidney.

Li., liver. (In Plate I the outline of its right dorsal lobe.)

Lu., anlage of lung.

Mes., mesentery.

M. P., portal mesentery, that part of C. M. caudad to the F. W.

N., notch between right dorsal hepatic lobe and C. M.

Ph., pharynx.

Re., position of renal anlage.

Sp. 0., spinal cord.

S. San, subcardinal spaces.

St, stomach.

U., venous loop through which the ureter passes.

U. V., Urnierenvene (Hochstetter).

Ur, ureter.

V. C., posterior cardinal vein. .

O. u., posterior cardinal vein, anterior division.

U. 11., posterior cardinal vein, posterior division.

c. m., vein extending into C. M. /v., vena cava, hepatic portion.

H. C., vena hepatica cornmunis.

L. T. P., posterior transverse lumbar vein.

V . m., small vein running into mesentery. In the plate similar ones, caudad, are not lettered.

V. m. x., vein running into mesentery and anastomosing with those of the opposite side.

V. O. M., omphalo-mesenteric vein. (Portal vein.)

V. P., portal vein, entering the liver from the M. P. V. R., renal vein.

V . Sp., subcardinal vein.

V . Sc. i., subcardinal vein, inferior division.

V. Sc. w., subcardinal vein, branch from Wolflian body.

V. U . d., right umbilical vein.

V. U. 8., left umbilical vein.

W. B., Wolifian body.

X., cross connection between subcardinals.

Y., cross connection between posterior cardinals.

A. I., intersegmental artery. In each plate only the first and last have been lettered.

A. M., mesonephric artery. In each plate only one of several has been lettered.

A. M. S., superior mesenteric artery.

A0., aorta

A. R., renal artery.

A. U., umbilical artery.

0. M., caval mesentery.

D. C., duct of Cuvier.

D. V. A., ductus venosus Arantii.

F. W., foramen of Winslow.

G. A., genital anlage.

Ht., heart.

Ki, kidney.

Li., liver. (In Plate I the outline of its right dorsal lobe.)

Lu., anlage of lung.

Mes., mesentery.

M. P., portal mesentery, that part of C. M. caudad to the F. W.

N., notch between right dorsal hepatic lobe and C. M.

Ph., pharynx.

Re., position of renal anlage.

Sp. 0., spinal cord.

S. San, subcardinal spaces.

St, stomach.

U., venous loop through which the ureter passes.

U. V., Urnierenvene (Hochstetter).

Ur, ureter.

V. C., posterior cardinal vein.

O. u., posterior cardinal vein, anterior division.

U. 11., posterior cardinal vein, posterior division.

c. m., vein extending into C. M. /v., vena cava, hepatic portion.

H. C., vena hepatica cornmunis.

L. T. P., posterior transverse lumbar vein.

V . m., small vein running into mesentery. In the plate similar ones, caudad, are not lettered.

V. m. x., vein running into mesentery and anastomosing with those of the opposite side.

V. O. M., omphalo-mesenteric vein. (Portal vein.)

V. P., portal vein, entering the liver from the M. P. V. R., renal vein.

V . Sp., subcardinal vein.

V . Sc. i., subcardinal vein, inferior division.

V. Sc. w., subcardinal vein, branch from Wolflian body.

V. U . d., right umbilical vein.

V. U. 8., left umbilical vein.

W. B., Wolifian body.

X., cross connection between subcardinals.

Y., cross connection between posterior cardinals.