426 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



of Lieberkiilm ; but just as the caecum is the recipient of the contents of 

 the ileum, and this often has an acid reaction, so may the contents of the 

 caecum be acid, especially in carnivorous animals, a fact which may serve 

 to illustrate the error of applying results found in carnivora to similar 

 functions in herbivora, where the processes are evidently different. 



Colin claims that the reaction of the contents of the caecum in the 

 horse is almost invariably alkaline, and that to a greater degree than in 

 the small intestine, whether the animal be digesting or fasting. When 

 an acid reaction has been found in this cavity it is almost invariably to be 

 explained as due to acid fermentations occurring in the- food-constituents. 



Ellenberger shows that the caecum has a special value in the horse. 

 In this animal, as we know, the small intestine is comparatively small, 

 with a relatively small extent of digestive mucous membrane. The 

 stomach is so small that it cannot contain the amount taken at one 

 meal, so the stomach forces its contents into the intestine even while the 

 animal is eating ; gastric digestion is, therefore, imperfect in these 

 animals. But, as the horse is nourished on substances which are diffi- 

 cult of digestion, it should possess a special digestive organ, which, by 

 its activity, should compensate for the loss of functional activity in the 

 stomach. Nothing can be more natural than to suppose that this sup- 

 plementary organ is found in the vast caecum of these animals, and w r e 

 may admit that this is to a certain extent true, without being compelled 

 to acknowledge that this organ liberates an acid digestive secretion. 

 The caecum is, hence, of special importance in the monogastric herbivora, 

 where the small size of the stomach prevents accumulation of food and 

 drink. It is, therefore, a reservoir for intestinal digestion. 



Its anatomical arrangement leads to the retaining of its contents. 

 Its bottom corresponds to the region of the xyphoid appendage, while 

 its narrow opening into the colon is in the most superior part, so that 

 everything to enter the colon must be forced up against gravity, and 

 should desiccation of its contents occur obstruction is sure to result, 

 and the result is apt to be fatal. In length it is about one meter, while 

 its capacity is from thirty-two to thirty-eight liters, or nearly twice as 

 large as the stomach. It has an extensive mucous membrane, well sup- 

 plied with glands, like the duodenal follicles (Fig. 164). 



Ellenberger reports a number of experiments which he made on the 

 horse to determine the length of time the food remains in the caecum 

 and the alterations to which it is subjected there. To determine this, he 

 fed a series of horses during a certain number of da}<s with a certain 

 amount of food of known composition ; the animals were then killed at 

 given periods, and the contents of the intestine examined. 



The results of these experiments showed that they might be divided 

 into four groups, according to the nature of the food given. 



