PANCREAS 



291 



branch ordinarily found descending from it in front of the pancreatic duct, 

 p. d., is not included. In some cases the accessory duct becomes imper- 

 vious, but it is generally functional, and if the outlet of the main duct were 

 blocked by gall-stones or otherwise, the presence of this accessory duct 

 would be of considerable importance. In some mammals, as in the pig, it 

 is normally the chief duct. 



The duct of the ventral pancreas either opens into the duodenum close 

 beside the common bile duct (Fig. 287, B), or it retains its embryonic rela- 

 tion (Fig. 287, A) and opens into the common bile duct near its duodenal 

 orifice. The duct of the ventral 

 pancreas, by an anastomosis 

 with the duct of the dorsal pan- 

 creas, becomes the outlet of the 

 main pancreatic duct, which was 

 first figured by Wirsung (1642). 

 It will be noted that a large part 

 of the dorsal pancreatic duct, 

 extending through the body and 

 tail, becomes incorporated in 

 this main duct of Wirsung; the 

 ventral pancreas supplies only 

 its outlet. 



In the adult no histological 

 distinction has ever been found 

 between the two pancreases, 

 but although alike in structure 



, , . , , , FIG. 288. SECTION OF HUMAN PANCREAS, SHOWING SBV- 



and Close together, there IS no ERAL ISLANDS. (Radasch.) 



_ i __ r 4. a, Interlobular connective tissue containing an interlobu- 



general anaStOmOSIS between l ar duct, c; b, capillary; d, interlobular duct; e, alveoli; 



.-. -n i i fi pancreatic island. 



them. Rarely they remain en- 

 tirely separate. Usually, on injecting the ducts, only one connection is 

 found between the dorsal and ventral pancreases, but in an abnormal case 

 two connections have been observed. Moreover, anastomoses between 

 the smaller ducts and tubules in the separate glands have not been found 

 in human adults. Rings of pancreatic tissue occur in the embryo, and in 

 adult guinea-pigs Bensley has demonstrated a free anastomosis of the 

 ducts (Amer. Journ. Anat., 1911, vol. 12, pp. 297-388); such a condition 

 has not yet been found in man. 



Microscopic structure. As a whole the pancreas somewhat resembles the 

 parotid gland. It is divided into lobes and lobules by connective tissue 

 septa containing blood and lymphatic vessels, nerves, and interlobular 

 ducts (Fig. 288). The lobules are composed chiefly of short tubules, or 

 alveoli, which in models appear pear-shaped; in sections they are cut 

 at all possible angles. Instead of exhibiting a well-defined lumen, the 



