240 The DevelopineJil 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 Wolffian 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 Wolffian 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 descrii^tion has been taken to mean that the vena cava inferior 

 developed downward from Ihe 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, " other- 

 wise the left vessel must be regarded as an independent anlage."' Grosser 

 (oi, p. 362) describes a similar condition in bats. " The right cardinal 

 vein stands already in broad connection with the posterior vena cava 

 which continues beyond this anastomosis along the median side of the 

 Wolffian body. A left Holilvenenanlage symmetrical with the right is 

 present, and joined to the right by one (or two?) almost capillary chan- 

 nels. Moreover, this vessel is united with the left posterior cardinal by 

 slender vessels, but this union plays no great role." Nevertheless, I con- 

 sider 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 Avhich united Avith the cardinal veins. 

 Those on the right could be followed to the hepatic vessels. This condi- 

 tion 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 Mdiich 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 Hochstetter 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." 



