GASTRIC DIGESTION. 371 



it was found that the percentage might be considerably increased above 

 this point and yet digestion go on. Thus, the gastric extract appeared 

 to possess about the same degree of activity when lactic acid was present 

 in 2 per cent, as with hydrochloric acid present in 0.2 per cent. The 

 ferment is only diffusible with great difficulty, and resists, to a high 

 degree, putrefactive and alcoholic fermentations. Lactic acid fermenta- 

 tion does not interfere with its activity. 



The ferment is soluble in water, glycerin, dilute acids, alkaline and 

 saline solutions, and loses its activity at 60° C. Such an artificial gastric 

 juice extracted from the mucous membrane of a horse's stomach will 

 digest animal tissues in the same way as extracts prepared from the 

 mucous membrane of the stomachs of carnivora. Extracts prepared 

 from inflamed mucous membrane are totally inactive. In addition to the 

 pepsin, the gastric juice of the horse also contains the milk-curdling fer- 

 ment and salts, lactic acid ferment, and traces of a diastatic ferment, all 

 of which may be precipitated by alcohol. The distribution of these 

 ferments and of the acidity of the gastric juice is the same as in the dog, 

 with the exception that no secretion takes place in the membranous car- 

 diac portion of this organ. 



Gastric digestion in solipedes is more important than one might be 

 led to suppose, and continues, to a certain extent, from one meal to the 

 next, as the residue remains in the stomach until the next one is taken, 

 and therefore the stomach does not completely empty itself after twenty- 

 four hours. The characters of this residue will, of course, vary with the 

 nature of the food. Thus, the contents of the stomach after feeding with 

 oats is a dried, crumbling mass, containing 60 to 70 per cent, of water. 

 After feeding with hay the percentage of water may be as much as 80 

 per cent. The reaction is always acid. 



Gastric juice obtained as above, by the method of Ellenberger and 

 Hofmeister, rapidly converts starch into sugar, although the ferment is 

 not derived from the stomach, but from the swallowed saliva. 



The change of starch into sugar goes on in the stomach, as is proved 

 by the fact that gastric juice outside of the body will turn starch into 

 sugar, and by the fact that after feeding starch large quantities of sugar 

 may be found in the contents of the stomach. The digestion of starch 

 is most active in the first two hours of digestion and stops after five or 

 six hours, when the percentage of hydrochloric acid is most marked. 



When dry food has been given, the conversion of starch into sugar 

 may continue much longer, from the large quantity of alkaline saliva 

 swallowed, and may go on in the left half of the stomach even while the 

 fundus is digesting proteids, the acidity being due to lactic acid. After 

 feeding with oats, as much as thirty-five grammes of sugar have been found, 

 while five to eight and one-half grammes of sugar have been found after 



