236 PEACTICAL PHYSIOLOGY 



the absorption of oil globules and that it acts as a laxative, but these 

 are not of much importance. It may be mentioned that in some animals 

 bile contains an amylolytic ferment. 



To sum up, we may state that although bile contains no ferment 

 by which a chemical change can be produced on any of the food-stuffs, 

 it is nevertheless of great value as a digestive fluid, in that it assists 

 the pancreatic juice (1) by neutralising the chyme ; (2) by dissolving 

 the fatty acid produced by the action of steapsin, and which has not 

 united with alkali to form soap ; (3) by assisting in the emulsification 

 of neutral fat ; (4) by assisting the absorption of fat, and consequently 

 (5) of allowing proteid to be attacked by trypsin, thereby diminishing 

 bacterial growth and consequent putrefaction ; (6) and lastly, by pre- 

 cipitating the half-digested products of chyme, so that the trypsin may 

 the better act on them. 



Intestinal Juice. This is secreted by Lieberkuhn's follicles. It may 

 be obtained pure by isolating a piece of intestine and collecting the 

 juice secreted by it. This may be accomplished by cutting out a piece 

 of intestine and stitching both ends to abdominal fistulae (Vella's 

 method), the severed ends of the intestine being sutured together. Or 

 one end of the isolated piece may be sutured, the other being attached 

 to a fistula (Thiry's method). In both these cases the mesentery of the 

 isolated portion is left intact, and the juice can be removed from the 

 loop and its action studied in vitro, or food may be placed in the loop 

 and afterwards removed and examined. 



Succus entericus seems to contain three ferments or ferment-like 

 bodies. One of these has been known for long and is called inverting 

 ferment because it 'inverts' (see p. 216) disaccharides. There are 

 several varieties of inverting ferment depending on the exact nature of 

 the disaccharide on which they act: e.g. one acting on maltose (makase), 

 one on lactose (lactase), and one on cane sugar (invertine). Lactase is 

 present only when the food contains lactose. 



The other two ferments act on proteids. One of them, erepsin by 

 name, hydrolyses casein, proteoses and peptones into simple nitrogenous 

 crystalline products, similar to those obtained when trypsin or strong 

 acids act on native proteids. It, itself, cannot however act on native 

 proteids. It is more plentiful in extracts of intestinal mucous membrane 

 than 'in succus entericus. It is probably, therefore, an intracellular 

 ferment, some of it leaking out of the cells into the succus entericus. 

 Since the proteids (i.e. peptones) have to pass through these cells 

 during absorption they will come under the influence of erepsin. 



Another ferment-like body in succus entericus is entero-Jcinase. Alone, 

 it has no action on any food stuff, but when mixed with trypsinogen it 



