222 A MANUAL OF VETERINARY PHYSIOLOGY 



in masses, to be forced out of the body at the next evacuation. 

 The reaction of this mass is acid, and the colour depends on the 

 food, being, on an ordinary diet, of rather a reddish-yellow or 

 brownish tint, due to altered chlorophyll. 



Absorption from the single colon and rectum is rapid ; the 

 marked change in the physical character of the faeces is evidence 

 of this. Animals may also be killed by the rectal injection of 

 strychnine ; narcosis can be produced by the rectal administration 

 of ether, and life may be supported, at any rate for a short time, 

 by means of nutrient enemata. 



Intestinal Digestion in Ruminants. 



Though intestinal digestion is so important in the horse, it 

 would appear in ruminants to occupy a subordinate position. It 

 is curious why in one animal the changes should occur at the 

 anterior, and in the other at the posterior part of the digestive 

 tract, but this difference in the arrangement for digesting cellulose 

 depends upon one being capable of rumination and the other not. 

 The rumen of the ox corresponds to the large intestines of the 

 horse. The intestines of the ox are of extreme length, but small 

 in calibre ; they are half as long again as those of the horse, and 

 it would appear that their chief function is that of absorption. 

 Their arrangement, especially that of the large intestine, is most 

 singular. The small intestines are hung in convolutions on a 

 mesentery ; they are narrow in diameter, and about 120 feet in 

 length. The large intestines are about 9 metres (30 feet) in 

 length, also narrow and without muscular bands or puckerings, 

 as in the horse ; the colon is arranged in a remarkable spiral 

 manner between the folds of the mesentery (see Fig. j8). It is 

 in this immense length of absorbent surface that the food sub- 

 stances capable of being utilised are taken up. It is clear, 

 however, that certain digestive changes occur in the small 

 intestines, into which, as in other animals, the pancreatic and 

 biliary fluids are poured. Here the proteins which have escaped 

 the stomach, and the fats and starches, are rapidly changed and 

 rendered -fit for assimilation ; the altered cellulose in all proba- 

 bility only finds its way here when fit for absorption after its 

 digestion in the rumen. 



Intestinal Digestion in other Animals. 



In the pig intestinal digestion is said to be of short duration, 

 and absorption very rapid. In the dog the material passes out 

 of the stomach slowly, and only in small quantities, into the 

 small intestines, which are usually found collapsed. It is in the 



