Digestion. 129 



Starch is not converted in the mouth, but it is in the 

 stomach by means of a starch- converting ferment contained 

 in the oats, which is capable of acting in the presence of 

 lactic acid. My observations on this subject are incomplete, 

 and therefore unpublished. 



After this, and with what we have to say on the cellulose 

 ferment, we need seek for no other explanation of the reason 

 why oats are so universally adopted as food for horses. 



According to Ellenberger, starch is the first substance 

 digested in the stomach of the horse, a diastatic ferment 

 existing in the left inert sac, and also in the fundus. 



Starch when attacked by a diastatic ferment is first 

 converted into soluble starch, then into dextrin, and lastly 

 into sugar ; part of the starch may be converted into lactic 

 acid by lactic fermentation. 



Fats are not acted upon in the stomach, though the 

 envelope surrounding the fat globule is digested, and the 

 fat set free. 



Milk is curdled in the stomach by means of the rennin ; 

 the casein thus produced is converted into peptones in the 

 ordinary manner. 



Cellulose fermentation is considered by Tappeiner to 

 occur in the left sac of the stomach, and when marsh-gas 

 has been found in this organ, it results from cellulose 

 decomposition. Ellenberger lays no stress on these results, 

 but recently Brown * has shown that the destruction of the 

 cell-wall of oats and barley occurs in the stomach, where it 

 is dissolved by a cyto-hydrolytic ferment pre-existent in 

 the grain. The changes occur with extraordinary rapidity 

 in the stomach of the horse. The researches of this 

 observer on a cellulose-dissolving ferment are of the 

 greatest interest to the veterinary physiologist, and of con- 

 siderable practical importance. 



The Various Periods of Stomach Digestion. — From what 

 has been previously said, it will be seen that digestion in 

 the stomach of the horse may be divided into certain 



* ' On the Search for a Cellulose-dissolving Enzyme,' H. J. Brown, 

 F.R.S., Journal of the Chemical Society, 1892, p. 352. 



9 



