SEC. 4. THE PROPERTIES AND CHARACTERS OF BILE, 

 PANCREATIC JUICE AND SUCCUS ENTERICUS. 



244. In the living body the food, subjected to the action 

 first of the saliva and then of the gastric juice, undergoes in the 

 stomach changes which we shall presently consider in detail, and 

 the food so changed is passed on into the small intestine, where it 

 is further subjected to the action of the bile secreted by the liver, 

 of pancreatic juice secreted by the pancreas, and possibly to some 

 extent, though this is by no means certain, of a juice secreted by the 

 intestine itself, and called succus entericus. It will be convenient 

 to study the minute structure of the liver in connection with other 

 functions of the liver more important perhaps than that of the 

 secretion of bile, namely the formation of glycogen, and other 

 metabolic events occurring in the hepatic cells ; we have already 

 studied the structure of the pancreas ; and the structure of the 

 intestine will best be considered by itself. We therefore turn at 

 once to the properties and characters of the above-named juices. 



Bile. 



Though bile, after secretion in the lobules of the liver, is passed 

 on along the hepatic duct, it is in the case of most animals not 

 poured at once into the duodenum but taken by the cystic duct to 

 the reservoir of the gall-bladder. Here it remains, until such time 

 as it is needed, when a quantity is poured along the common bile 

 duct into the intestine. 



The quality of bile varies much, not only in different animals, 

 but in the same animal at different times. It is moreover affected 

 by the length of the sojourn in the gall-bladder ; bile taken direct 

 from the hepatic duct, especially when secreted rapidly, contains 

 little or no mucus; that taken from the gall-bladder, as of 

 slaughtered oxen or sheep, is loaded with mucus. The colour of 

 the bile of carnivorous and omnivorous animals, and of man, is 

 generally a bright golden red, but in man may be a greenish 

 yellow; that of herbivorous animals is a yellowish green, or a 



