314 DIGESTION. 



excretion or non-absorption of fatty matter should be 

 ascribed. In Bernard's experiments too, fat always ap- 

 peared in the evacuations when the pancreas was destroyed 

 or its duct tied. Bernard, indeed, is of opinion that to 

 emulsify fat is the express office of the pancreas, and the 

 evidence that he and others have brought forward in sup- 

 port of this view is very weighty. The power of emulsify- 

 ing fat, however, although perhaps mainly exercised by 

 the secretion of the pancreas, is evidently possessed to 

 some extent by other secretions poured into the intestines, 

 and especially by the bile. 



3. The pancreatic secretion discharges a third function 

 also, namely, that of dissolving albuminous substances ; 

 the peptone produced by the action of the pancreatic secre- 

 tion on proteids not differing essentially from that formed 

 by the action of the gastric juice (see p. 285). 



Structure of the Liver. 



The liver is an extremely vascular organ, and receives 

 its supply of blood from two distinct vessels, the portal 

 vein and hepatic artery, while the blood is returned from it 

 into the vena cava inferior by the hepatic vein. Its secre- 

 tion, the bile, is conveyed from it by the hepatic duct, either 

 directly into the intestine, or, when digestion is not going 

 on, into the cystic duct, and thence into the gall-bladder, 

 where it accumulates until required. The portal vein, 

 hepatic artery, and hepatic duct branch together throughout 

 the liver, while the hepatic vein and its tributaries run by 

 themselves. 



On the outside the liver has an incomplete covering of 

 peritoneum, and beneath this is a very fine coat of areolar 

 tissue, continuous over the whole surface of the organ. 

 It is thickest where the peritoneum is absent, and is con- 

 tinuous on the general surface of the liver with the fine, 

 and, in the human subject, almost imperceptible, areolar 

 tissue investing the lobules. At the transverse fissure it is 



