296 COMPARATIVE ZOOLOGY 



and is especially distinguished from other such solutions 

 by its diff usibility i.e., the ease with which it passes 

 through a membrane. Some of these peptones, with 

 the sugars of the food, whether original or the product 

 of the action of the saliva, are absorbed from the stomach. 

 The food, while in the stomach, is kept in continual 

 motion, and, after a time, is discharged in gushes into 

 the intestine. The name chyme is given to the pulpy 

 mass of food in the stomach. 103 In the intestine the 

 chyme meets three fluids bile, pancreatic juice, and 

 intestinal juice. All of these are alkaline, and at once 

 give the acid chyme an alkaline reaction. This change 

 permits the action of the saliva to recommence, which 

 is aided by the pancreatic and intestinal juices. The 

 pancreatic juice has much more important functions. 

 It changes albuminoid food into peptones, and probably 

 breaks up the fats into very small particles, which are 

 suspended in the fluid chyle. This forms an emulsion, 

 like milk, and causes the chyle to appear whitish. The 

 bile has important functions, but little understood. It 

 emulsifies and saponifies part of the fats, so that they 

 are dissolved, and perhaps aids in preventing the food 

 from decomposing during the process of digestion and 

 absorption. The chyle is slowly driven through the 

 small intestine by the creeping, peristaltic motion of its 

 walls, 104 the nutritious portion being taken up by the 

 absorbents, as described in the next chapter, while the 

 undigested part remaining is discharged from the large 

 intestine. 105 * 



