“ 
eae a 
ing a prominent ridge on its upper (primitive left) surface. On 
approaching the duodenum, this ridge becomes still more prominent 
(Fig. 3 vv), and at one place the peritoneum entirely surrounds the 
vessel, which at this point is free from the surface of the mesentery, 
The vein finally passes under the duodenum to enter the liver. 
Just below the duodenum, a branch from the vitelline vein extends 
out into the mesentery, aud in the sections is found to accompany 
the vitelline artery. This branch evidently represents the superior 
mesenteric vein of the adult. The vitelline vein (distal to the duodenum) 
already shows sign of involution. Its walls are thickened, and its 
lumen very narrow, in places almost obliterated. No such changes 
are seen in the vitelline artery, however. Ä 
That the vitelline (omphalomesenteric) vein does not persist as 
the superior mesenteric vein was noted long ago by LuscuKa (10). 
He states that the omphalomesenteric vein‘) disappears in man in 
embryos of the third month, but can still be injected through the 
heart at birth in the carnivora which are born blind (dog, cat, etc.). 
ALLEN (1) confirmed these results in the dog, cat, lion, and guinea pig. 
These results, however, have evidently been overlooked by many 
later writers. His (6) makes no mention of them in his elaborate 
work. He states that the omphalomesenteric vein becomes the superior 
mesenteric and the portal veins. The omphalomesenteric does become, 
in part, the portal vein, but evidently only a small portion of it 
becomes superior mesenteric vein (i. e., the portion from the point 
where it is joined by the branch which does represent the true superior 
mesenteric up to the point where it receives the splenic vein, forming 
the portal vein). , 
Minot (13) does not make a clear statement as to the relation 
of the vitelline vein to the superior mesenteric vein, and does not 
mention the atrophy of the vitelline vein. The same may be said of 
the text-books of Marsmatt (11), Mc Murricn (12), Young and 
Ropinson (14), HERTWIG (5), and others. 
Dexter (3) describes, apparently as an original observation, the 
atrophy of the omphalomesenteric vein in the fetal cat, and an in- 
dependent formation of the superior mesenteric vein. Lewis (9) later 
verified this condition for the pig, crediting DEXTER with the original 
discovery. 
Foster and BALFOUR (4), however, describe the superior mes- 
1) Luschka also included the artery in his statement, but this is 
evidently an error. 
