Frederic T. Lewis 241 



That the plan of development described for the rabbit is of wide ap- 

 plication is probable. Grosser has fonnd it in bats, Zumstein in the 

 mole, Hochstetter and Kollmann have indicated it in human embryos. 

 I have fonnd a similar arrangement in pigs, and note that the recon- 

 struction of the pig's veins by Minot (98, PI. I, Fig. 5) is incomplete. 

 Dr. Minot has pointed ont to me in the original reconstruction several 

 sectioned areas in the veins, omitted in the figure. xV more complete 

 drawing of these vessels is to appear in his " Text-book of Embryology." 



Finally a paragraph concerning nomenclature! The vena cava in- 

 ferior 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 pther sections of the adult ves- 

 sel the vena cava. I agree with D wight (01, p. 29) that it is quite 

 accurate to speak of the " cava below the diaphragm " or above the 

 diaphragm. 



SUMilAEY. 



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 cardi- 

 nal vein. 



Small vessels from the mesentery pass into the cardinals. They an- 

 astomose 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 l)oth ends, and bilaterally symmet- 

 rical in its early stages is the suhcardiual vein. 



, The cross connections between the subcardinal veins give place to a 

 single large cross anastomosis caudad to the origin of the superior mesen- 

 teric artery. Above this anastomosis the right subcardinal connects 

 with the liver and rapidly enlarges: the left subcardinal becomes very 



