DIGESTION. 87 



the proteids into peptones by various stages. The fats are split up 

 by a gastric lipase. Starch is unaffected. 



The general result is the "formation of a souplike mass in the 

 stomach. This undigested food is passed through the pylorus into 

 the duodenum of the small intestine, and is called chyme. The 

 average time that food remains in the stomach is about three hours. 



Giinzburg's Test for Hydrochloric Acid. With a solution of 

 phloroglucin and vanillin in alcohol mix a drop of a solution of 

 hydrochloric acid, 0.2 per cent. ; evaporate slowly in a porcelain cap- 

 sule, when a red color will appear. 



Uff elmann's Test for Lactic Acid. Add a trace of solution of 

 ferric chloride to a 1-per-cent. solution of carbolic acid. This ame- 

 thyst-colored solution will change to canary yellow on the addition 

 of lactic acid. 



VOMITING. 



Vomiting is a spasmodic rejection of food from the stomach, and 

 is usually a sign of some malady. The ease with which animals vomit 

 is dependent upon the conformation of the stomach, particularly with 

 regard to the fundus, as well as the condition of its contents. . Thus, 

 a child vomits easily, since its fundus is not very well developed; 

 with the adult the act is one of great difficulty. 



When the person is conscious, vomiting is usually preceded by a 

 sensation of nausea, during which the saliva flows very freely into 

 the mouth. While the food is being swallowed considerable air enters 

 the stomach, and later assists actual vomiting by helping to dilate the 

 cardiac orifice. Before the real expulsion occurs, and during the 

 efforts to accomplish the same, a very deep inspiration is taken just 

 as in the act of coughing. Immediately the glottis closes, and the 

 muscles of the abdomen commence to contract very actively. In- 

 stead of the glottis opening to permit an expiration,. it remains tightly 

 closed, thereby holding the diaphragm immovably fixed, and so 

 furnishing an unresisting plane against which the stomach is pressed. 

 Immediately preceding the pressure brought to bear upon the 

 stomach by the contraction of the abdominal muscles, there occurs 

 a shortening of the longitudinal fibers of the oesophagus, thereby 

 bringing the cardiac orifice of the stomach nearer the diaphragm, 

 to form a straight passageway for the vomit to the pharynx. The 

 muscles of the sphincter at the cardiac orifice are rather suddenly 

 dilated, forming a funnel-shaped opening at the beginning of escape, 

 since the pylorus usually remains closed. By the abdominal con- 



