116 The Feeding of Animals 



relation to digestion. If any ferment is present at all, 

 it is only as a trace, and therefore the bile is incapable 

 of effecting decompositions of the proteids and carbo- 

 hydrates, such as occur in the mouth and stomach. 

 This is shown by experiments. 



Nevertheless, this liquid must be regarded as having 

 a real digestive function, which it exerts in two ways, 

 (1) by preparing the chyme (partially digested food 

 from the stomach) for the action of the pancreatic juice 

 and (2) in acting upon the fats in such a way as to 

 render their absorption possible. 



We have learned that pepsin, the stomach ferment, 

 acts upon proteids only in an acid medium. The oppo- 

 site is true of the ferments which the food meets in the 

 intestines, for these require an alkaline condition. The 

 bile tends to neutralize the acidity of the chyme, and in 

 this, as well as by other chemical changes too complex 

 for discussion here, prepares the way for the pancreatic 

 juice to do its work. 



The most important discovery so far made in con- 

 nection with the bile is the fact that when its entrance 

 into the intestines is prevented the fat of the food 

 largely passes off in the feces. This proves that in 

 some way the liver secretion is essential to the digestion 

 of fats. The ordinary and probably correct explanation 

 of what takes place is that, while bile does not decom- 

 pose the fats in any way, it is able, in connection with 

 certain influences of the pancreatic juice, to reduce them 

 to an emulsion, i. e., to a condition of suspension in a 

 liquid in very finely divided particles, a form in which 

 are able to pass into the blood. It is believed 



