Fred W. Thyng 501 
adult (Owen, 68, and others) where the duct of the dorsal pancreas 
opens into the intestine beyond the opening of the common bile duct. 
These cases, however, must be exceptions to the normal condition. My 
evidence for this conclusion is derived from a study of these ducts in the 
following series of eighteen human embryos in the Harvard Embryologi- 
eal Collection: 256 (7.5 mm.), 817 (8 mm.), 529 (9.4 mm.), 1005 (9.4 
mm.), 1001 (9.6 mm.), 1000 (10 mm.), 736 (10.2 mm.), 816 (12 mm.), 
839 (13.6 mm.), 1003 (14.5 mm.), 1128 (16 mm.), 1129 (18.1 mm.), 
819 (19 mm.), 828 (19 mm.), 851 (22 mm.), 871 (22.8 mm.), 181 
(23 mm.), and 38 (24 mm.). In every one of these embryos the duct of 
the dorsal pancreas was found’ to be nearer the stomach than the intes- 
tinal opening of the common bile duct. 
SUMMARY. 
From the preceding study it is seen that in the pig, rabbit, cat, and 
man, there is a dorsal and a ventral pancreas. In the eighteen human 
embryos examined the dorsal pancreas arises from the intestine distinctly 
anterior to the hepatic diverticulum, and in the human adult its duct is 
generally found to be nearer the stomach than the orifice of the bile duct. 
In the pig, rabbit, and cat, the duct of the dorsal pancreas opens into the 
duodenum beyond the bile duct. 
In the rabbit and the pig the dorsal pancreas shows, very early in its 
development, distinct right and left lobes spreading from a common 
stem; such lobes were not found in human embryos. ‘The ventral pan- 
creas is often described as arising from independent right and left halves, 
of which the left very soon disappears. The present study has shown no 
sufficient reason for subdividing the ventral pancreas into two independ- 
ent lateral parts. 
The dorsal pancreas sends a ventral process on the right side of the 
right vitelline vein, to fuse with the ventral pancreas. This process is 
well developed in the pig and rabbit. In the cat of 10.7 mm. it is indi- 
cated, and in the adult cat it is sometimes present and sometimes absent 
(Heuer). In the human embryo it did not occur, and in the pancreas of 
the human adult its existence has apparently not been recorded. 
By the development of the duodenal loop and associated with the rota- 
tion of the stomach, the dorsal pancreas is brought into contact with the 
ventral pancreas at a second point. Here, on the ventral side of the por- 
tal vein, the two anastomose. In those cases in which the ventral process 
has fused with the ventral pancreas, a ring of pancreatic tissue surround- 
