252 DIGESTION. 



fatty matters, by transforming them into a kind of emulsion, 

 and thus rendering them capable of absorption by the lacteals. 

 Several cases have been recorded in which the pancreatic duct 

 being obstructed, so that the secretion could not be discharged, 

 fatty or oily matter was abundantly discharged from the in- 

 testines. In nearly all these cases, indeed, the liver was eoin- 

 cidently diseased, and the change or absence of the bile might 

 appear to contribute to the result ; yet the frequency of exten- 

 sive disease of the liver, unaccompanied by fatty discharges 

 from the intestines, favors the view that, in these cases, it is to 

 the absence of the pancreatic fluid from the intestines that the 

 excretion or non-absorption of fatty matter should be ascribed. 

 In Bernard's experiments too, fat always appeared in the 

 evacuations when the pancreas was destroyed or its duct tied. 

 Bernard, indeed, is of opinion that to emulsify fat is the ex- 

 press office of the pancreas, and the evidence that he and 

 others have brought forward in support of this view is very 

 weighty. The power of emulsifying 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 secretion on proteids 

 not differing essentially from that formed by the action of the 

 gastric juice (see p. 229). 



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 secretion, 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 peri- 

 toneum, 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 continuous on the 

 general surface of the liver with the fine, and, in the human 

 subject, almost imperceptible, areolar tissue investing the 



