88 NUTRITION OF FARM ANIMALS 



two ways, namely by neutralization and precipitation, the pep- 

 sin is prevented from digesting the enzyms of the pancreatic 

 juice and bile, an action which would otherwise take place, since 

 these enzyms appear to be substantially protein in their nature. 1 

 In the small intestine, the neutralized contents of the stomach 

 are subjected to the combined action of the pancreatic juice, 

 the bile and the intestinal juice, while they are moved along 

 through the successive divisions of the small and large intestines 

 by means of the peristaltic movements of the latter. These 

 movements serve also to mix the contents of the intestines 

 and to bring them into intimate contact with the intestinal 

 walls. 



The fats of the feed, under the action of the steapsin of the 

 pancreatic juice, undergo a cleavage into glycerol and fatty 

 acids and this change is considerably accelerated by the bile, 

 which also aids in emulsifying the fats and so exposing vastly 

 more surface to the action of the enzyms. The fatty acids 

 thus set free unite to a greater or less extent with the alkali of 

 the pancreatic juice and bile, forming soaps, while both soaps 

 and free fatty acids are soluble in bile in the presence of sodium 

 carbonate. The presence of soaps in solution also aids, as was 

 pointed out in Chapter I, in producing a permanent emulsion 

 of the fats. 



Starch, if any escapes digestion in the stomach, is acted upon 

 by the pancreatic amylopsin substantially in the same manner 

 as by the ptyalin of the saliva but much more energetically, 

 yielding maltose, while both maltose and any other disaccharid 

 present in the feed are acted upon by the invertases of the in- 

 testinal juice, yielding monosaccharids. 



Any proteins which escape digestion in the stomach, and 

 likewise the proteoses and peptones resulting from peptic di- 

 gestion, are hydrolyzed by trypsin and erepsin much more 

 energetically than by pepsin and yield not only proteoses and 

 peptones, but a whole series of progressively simpler poly- 

 peptids and finally are largely or wholly split up into their 

 constituent amino acids. 



1 The foregoing statements describe what takes place when the materials are 

 mixed in the laboratory. The actual importance of the precipitation of the pepsin 

 in the intestine is somewhat in doubt. 



