76 STRUCTURE AND' ECONOMY OF THE nORSE. 



other by the liver. The pancreatic juice is very similar to that 

 of saliva ; its principal use, therefore, appears to be to dilute the 

 food ; but it also contains much albumen, which forms an import- 

 ant constituent in chyle. Wc can readily understand how essen- 

 tial it is that a watery fluid should here be supplied. In the 

 stomach it would be unnecessary, indeed hurtful, as it would 

 hasten the expulsion of its contents too rapidly ; but in the 

 intestines, in order that the chyle should be extracted, it is essen- 

 tial that the food should be liquefied. 



The formation of chyle is the immediate result of the admix- 

 ture of the bile, which thus has a chemical action on it. 



The properties of bile have before been noticed, and its prin- 

 cipal use is that above stated. 



Chyle is a thick white fluid, resembling cream, when recently 

 extracted, but it soon separates into a coagulum and a watery 

 fluid: it is found to be composed of minute globules, smaller 

 than those of the blood : its taste is both sour and sweet. 



The chyme, when it enters the duodenum, has a considerable 

 quantity of acid in its composition ; but as it advances it is 

 deprived of this acid, and alkali is found to preponderate. This 

 change is effected by the bile, which contains a large quantity of 

 alkali, the alkali combining with the muriatic acid of the chyme. 

 By this combination carbonic acid is set free, which accounts for 

 the presence of this gas in the intestines. There are other gases 

 found in the intestinal canal, which in the stomach principally 

 consist of oxygen and nitrogen, and, in the large intestines, of 

 hydrogen in several combinations. 



The greater part of the chyle is extracted in the small intes- 

 tines by means of the lacteals ; but in the large intestines also 

 this process goes on : for it has been found that life has been 

 supported for some time by nutritious injections. 



The food having entered the large intestines, is prevented from 

 returning by the valve at the place of entrance. The colon and 

 the cajcum commence from the same place, so that a portion of 

 the food enters each intestine. On examinino; the cajcum after 

 death, we find that its contents are more watery than the others; 

 and it has been found that when a horse takes a large quantity 

 of water, it passes in the course of ten minutes into the caecum, 

 whose principal oflace may therefore be considered as a re- 

 ceptacle for water. The importance of such a reservoir in the 

 horse is very evident, when we consider, on the one hand, the 

 small size of the stomach, and, on the other, the large quantity of 

 water, three or four gallons, taken at a time. A great portion of 

 the contents of the caecum is taken up by the absorbent vessels, 

 and the remainder is returned to the place of entrance, and 

 passes into the colon and mixes with its contents. The structure 

 ot the colon we have before noticed : its interior is formed into 



