33 8 Elementary Biology. 



known as peptones. The involuntary churning movements 

 which take place in the stomach act in the same manner 

 as the voluntary movements of the buccal cavity in pro- 

 moting a perfect mixture of the gastric juice and the 

 food. 



The action of these two fluids, therefore, is to render 

 two important constituents of the food, starch and albumin, 

 soluble and capable of being absorbed through the walls of 

 the intestine. 



The food, or chyme, as it is termed, after being 

 acted on by gastric juice, now passes into the intestine, 

 where it meets with intestinal juice. This fluid is secreted 

 from the Lieberkiihnian follicles in the wall of the intestine, 

 and appears to have much the same action upon the 

 intestinal contents as the pancreatic juice has ; we may 

 simplify matters, therefore, by considering these together. 

 The pancreatic juice contains three ferments, all important 

 in their nature. The first and characteristic ferment of the 

 pancreas is trypsin, which has the power of transforming 

 proteids which have escaped the action of the peptic ferment 

 into peptones but here in an alkaline medium, while pepsin 

 only acts in an acid medium. Further, the pancreatic juice 

 contains a ferment which acts on fats or oils so as to 

 transform them into an emulsion, in which the oil occurs 

 in extremely fine particles ; it then decomposes them into 

 glycerin and their corresponding fatty acids (p, 28). 

 Lastly, the fatty acid forms soaps with the alkali present in 

 the juices of the pancreas and intestine. Pancreatic juice 

 is also able to change starch into sugar should any be left 

 over unacted upon by the saliva. Where salivary glands are 

 absent, as in the frog, the pancreas is the only agent in this 

 process. 



Bile. The character and functions of this fluid have 

 been sufficiently referred to in connection with the liver 

 (p. 280). We may briefly summarise its uses by saying that, 

 while acting as a stimulant on the intestinal mucous mem- 



