f'rederic T. Lewis 



235 



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 botli vessels into superior and in- 

 ferior parts. The superior portion of the subcardinal enlarges, its 

 inferior division diminishes, and correspondingly the inferior section of 

 the cardinal enlarges, its superior part Ijecomes small. Tbus the inferior 



V.Sc. 



A. M.S. 



Fig. 8. Rabbit embrj-o of 11 mm., 14 days. x 2S. This series is not one of the 

 Harvard Collection. 



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. 



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, PI. I, shows 

 the anterior part of the cardinal, Y. C. a., separated from the posterior 

 division, Y. C p. On the left side, however, tlie 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, 

 PI. II. The cardinal veins are now both sulidivided as just described. 



