Digestion. 135 



digestion of the stomach in some animals is far from rare. 

 No perfectly satisfactory solution of the problem has yet 

 been afforded ; the alkalinity of the circulatory blood is not 

 considered to meet the difficulty. In an extensive post- 

 mortem experience amongst horses, I have never yet met 

 with post-mortem digestion of the stomach. Whether this 

 is due to the horse's acid being mainly or wholly lactic, I 

 cannot say. 



The Gases of the Stomach. — The nature of these largely 

 depends upon the food; traces of oxygen, a quantity of 

 carbonic acid, and variable amounts of marsh-gas, sul- 

 phuretted hydrogen, hydrogen, and nitrogen are found. 

 The oxygen and nitrogen are derived from the swallowed 

 air ; the carbonic acid is derived from the fermentation of 

 the food, and the action of acids on the saliva ; and the 

 marsh-gas is obtained by the decomposition of cellulose. 



Tappeiner found the following gases in the stomach of 

 the horse : 



Carbonic acid - - - 75*20 07"73 



Oxygen - - - -23 "00 



Hydrogen - - - 14-56 12-66 



Nitrogen - - - 9'99 19\54 



I have found in the stomach of a horse in perfect health, 

 which had been fed on oats, the following gases in every 

 100 volumes : 



Carbonic acid - - - - - 2 1 "2 



Oxygen - - - 11*8 



Hydrogen ... - o - 6 



Nitrogen - - - 61 "4 



but I take it that the proportion of these gases must vary 

 considerably, and depend largely on the diet. 



In cattle, by feeding on hay, the following gases were 

 found by Tappeiner in the rumen : 



