DiaBSTION OF POOD. 



365 



Deglutition is the result of the co-ordinated action of many 

 muscular mechanisms, and is reflex in nature. The oesophagus 

 secretes mucus, which lubricates its walls, and aids mechan- 

 ically in the transport of the food from the mouth to the stom- 

 ach. In the stomach, by the action of the gastric juice, food 

 is further broken up, the proteid covering of fat-cells is digested, 

 and the structure of muscle, etc., disappears. Proteid matters 

 become peptone, and in some animals fat is split up into free 

 fatty acid and glycerin ; but the digestion of fat in the stom- 

 ach is very limited at best and probably does not go on to 

 emulsification or saponification. The digestion of starch con- 



FiG. 288. — Matters taken from pyloric portion of Blomach of dog during digestion of 

 mixed food (after Bernard), a, disintegrated muscular fibers, strise navmg disap- 

 peared; &, c, muscnlar fibers in wliicli strise have partly disappeared; d, d, a, glob- 

 ules of fat; e, g, starch; g, molecular granules. 



tinues in the stomach until the reaction of the food-mass be- 

 comes acid. This in the hog may not be far from one to two 

 houys, and the amylolytic ferment acts with great rapidity even 

 without the body. The food is moved about to a certain ex- 

 tent, so as to expose every part freely to the mucous mem- 

 brane and its secretions. It is likely that the sugar resulting 

 from the digestion of starch, the peptones, and, to some ex- 

 tent, the fat formed (if any), is received into the blood from 

 the stomach. 



