31>4 FREDEHIC T. LEWIS 



cases the left lobe is longer but more slender than the right. The 

 four models just described explain the contradictory conclusions 

 of Wlassow and Volker. Wlassow states that "the ventral pan- 

 creas is very distinctly two-lobed." Volker finds that "in its 

 origin it is not two-lobed, since it bends at once to the right." 

 Both forms were found by Hilton, who modelled the ventral 

 pancreas in two embryos, the ages of which he estimated at 17| 

 and 20 days respectively. Presumably they measured between 

 6 and 7 mm. Since the In-lobed form occurred in the younger 

 specimen, Hilton suggested that it might be an earlier stage. 



The student collection at the Harvard Medical School, which 

 includes serial sections of 150 pig embryos measuring from 10 to 12 

 nnn., affords an unusual opportunity for determining the frequency 

 of the bi-lobed form. In seventeen specimens (11.3 per cent), 

 the left lobe is well developed. In seven additional cases, a 

 "small wing or projection from the main mass suggests a rudimen- 

 tary left lobe. When present, the left lobe varies in position. 

 Usually it crosses the root of the ventral mesentery, and it may 

 terminate near the dorsal pancreas (fig. 8). In three embryos, 

 the left lobe descends along the mesenteric attachment, and in 

 one of these it terminates within the mesentery (fig. 9). Fre- 

 quently a nodule of cells, or a small cyst, is seen on the hepatic side 

 of the mesentery (as shown at x in fig. 10). Because of the possi- 

 bility that these may have been detached from the left lobe of 

 the ventral pancreas, they were carefully examined. 



Among 100 embryos, the nodules or cysts were found in 51 

 specimens. Often two or three occur in a single embryo. They 

 are generally located close to the peritoneal epithelium and fre- 

 (juently they are found at the sunnnit of a connective tissue ele- 

 vation, as in fig. 10. This elevation does not always coincide 

 with the line of mesenteric attachment. The nodules may occur 

 at any point along the peritoneal covering of the gall bladder, and, 

 near its tip, where the peritoneum invests it on all sides, they are 

 found toward the ventral body wall. Occasionally they are seen 

 deep within the connective tissue layer which surrounds the gall 

 bladder, and often they are found in actual connection with the 

 hepatic trabeculae at the sides of this layer. Some of them there- 



