212 PHYSIOLOGY CHAP. 



Klihne gave it the name of amphopeptone. In pancreatic 

 digestion, on the contrary, the two groups of amphopeptone are 

 split up, and give rise to hemi- and anti-peptone. 



There can be no doubt that hemipeptone breaks up under the 

 proteolytic action of trypsin, independent of any process of 

 putrefaction, for when pancreatic extract treated with salicylic 

 acid is digested in vitro for a long time, amino-acids and other 

 products of protein decomposition are constantly met with. 



Before inquiring whether this advanced proteolytic process 

 takes place under physiological conditions in the intestine, as it 

 does in artificial digestions, we will examine the chemical action 

 of bile and succus entericus upon the food-stuffs. 



The digestive action of bile in vitro is very insignificant. It 

 has no stronger solvent action on proteins than water. Some 

 authors (Klihne, v. Wittich, Giannuzzi, and G. Bufalini) have 

 recognised a slight diastatic action on starch from the bile of man 

 and some other mammals, which is probably due to small quantities 

 of ptyalin or amylopsin from the salivary glands or from the 

 pancreas, absorbed by the roots of the portal system, and recon- 

 ducted from the liver to the intestine with the bile. 



The emulsifying (not lipolytic) action of the bile upon the 

 alimentary fats, which invariably contain a small amount 

 of free fatty acid (supra), is more important. As early as 1858 

 Marcet noted that if bile be added to fats mixed with oleic, 

 palmitic, or stearic acid, a part of the latter at once decomposes 

 the bile salts, and combines with the liberated alkalies to form 

 soaps, which produce a fine emulsion of neutral fats. When the 

 ordinary alimentary fats are employed, however, the emulsion 

 produced by the bile is rather coarse and unstable, owing to the 

 small amount of free acids which they contain. 



In studying the digestive action of succus entericus in 

 vitro, either the glycerol extract of intestinal mucous membrane 

 or the juice that flows from a Thiry-Vella fistula after injection of 

 pilocarpine, may be employed, or the juice can be collected on small 

 sponges introduced into the loop of intestine. In these artificial 

 digestions, all trace of putrefaction must be avoided by adding a 

 few drops of alcoholic solution of thymol or salicylic acid (Masloff), 

 or still better iodoform (Vandevelde). 



Provided the digestion of succus entericus in vitro proceeds 

 under aseptic conditions, it has been proved to exert no action on 

 protein, e.g. meat, egg-white, etc. On the other hand, 0. Cohnheirn 

 finds that it does act on proteoses and peptones, which are split 

 into amino-acids, owing to the specific proteolytic action of erepsin. 

 It further has the property of curdling milk by a process of casei- 

 fication, which, unlike that in the stomach, occurs in an alkaline 

 medium (Vella). This effect is due to chymosin, which is present 

 in small amounts in the succus entericus of certain animals. 



