114 A Manual of Veterinary Physiology. 



to whether more than one kind of food is partaken of at the 

 same time; bulky food, such as hay, passes out more rapidly 

 than condensed food, such as oats. Oats contain consider- 

 ably more nitrogenous matter than hay, therefore a longer 

 period must be devoted to their digestion in the stomach : 

 we will, therefore, consider first of all the digestion of hay, 

 then that of oats. 



Digestion of Hay. — Hay, as we have shown, mixes in the 

 mouth with four times its bulk of saliva, and after a very 

 perfect grinding passes into the stomach ; assuming the 

 stomach to be empty, it passes at once to the right side ; 

 the gastric juice begins to act, and, as before described, 

 chyme commences to pass into the intestines probably in a 

 very imperfectly elaborated form. Assuming the animal to 

 have finished the hay, we now find the output into the 

 intestine becomes small and slow ; the gastric juice has an 

 opportunity of acting upon the ingesta, which turns yellow 

 on that surface in contact with the stomach-wall ; the 

 compression of the latter on the contents causes them to 

 become distinctly moulded into a mass, the shape of the 

 stomach, being more fluid towards the pylorus than else- 

 where. The greater curvature in all probability is fuller 

 than the lesser. The material is perfectly comminuted, 

 and resembles firm, dry, green and yellow fajces, and the 

 smell is peculiar, like sour tobacco. 



The yellowness is due to the gastric juice, and is conse- 

 quently more marked towards the pylorus ; the portion 

 coloured green is the part as yet unacted upon by the juice. 

 The total surface of the stomach and its contents are now 

 acid, though Colin says otherwise. The acidity is greater at 

 the fundus than at the cardia. This acidity shows that a 

 diffusion of the gastric juice must have been going on. 

 There is no evidence of any churning motion, the cake- 

 like condition into which the hay is compressed in spite of 

 its four equivalents of saliva is due to the compression of 

 the material by the stomach walls. 



The duration of stomach digestion of hay is variable, but 

 I quote one or two of Colin's experiments. A horse 



