The Animal Body. 223 



Digestion in the intestine. When the food leaves the stomach 

 it enters the small intestine. At this point it is only partially 

 digested. The fats of the food have not as yet been changed, 

 and undoubtedly a considerable proportion of the proteins and 

 carbohydrates susceptible to solution is still to be acted upon. 

 Immediately after passing from the stomach, the partially di- 

 gested mass comes in contact with the pancreatic juice, the bile 

 and intestinal juice, and the changes which began in the mouth 

 and stomach, together with others which set in for the first time, 

 proceed at a vigorous rate. The bile is secreted by the liver and 

 stored in the small sac attached to that organ and called the 

 "gall bladder" and from which it is brought to the intestine by 

 a duct opening near the orifice leading out of the stomach. Bile 

 is a reddish-yellow (in carnivorous animals) or green (in herb- 

 ivora) liquid, with an alkaline reaction and bitter taste. It con- 

 tains complex salts, which in conjunction with the fat splitting 

 enzyme of the pancreatic juice, reduces the fats to an emulsion, 

 a form in which they can be absorbed into the blood. When bile 

 is prevented from entry into the intestine, the fat of the fowl 

 largely passes out in the feces. Besides this important relation 

 to fat digestion, the bile also acts in some degree as an anti- 

 septic, preventing putrefaction in this part of the intestine. 



The pancreatic juice is of strongly alkaline reaction due to its 

 content of sodium carbonate, and is characterized by the pres- 

 ence of at least three distinct enzymes ; these are trypsin, a pro- 

 tein digesting ferment ; lipase, a fat splitting enzyme ; and amy- 

 lopsin, a starch digesting enzyme. This juice comes from the 

 pancreas and enters the intestine through a small duct, which 

 in some animals is confluent with the bile duct. By the action of 

 this juice, the acid chyme from the stomach is rapidly converted 

 into an alkaline mass and the enzyme pepsin is quickly destroyed 

 in the new environment. Trypsin, effective in alkaline media, 

 now continues the protein digestion, splitting the proteoses and 

 peptones, as well as unattacked proteins, into simpler structures. 

 In this act it is aided by another enzyme, known as erepsin, 



