FUNCTIONS OF QUADRUPEDS. 11 



of this is, that the food is not long detained in it, but 

 quickly forward towards the other intestines. 



It is in the intestines that the aliments undergo that change 

 which fits them for nutrition. The nutritive part is absorb- 

 ed, during the act of digestion, by very small vessels which 

 conduct it into the circulation. These vessels are called 

 lacteals, and are furnished internally with valves, all opening 

 in a direction towards the heart, in which direction the fluid 

 they convey has to flow. The chyle, or white liquor 

 produced by digestion, after having come in contact with 

 the air in the organs of respiration, mixes with the blood, 

 and is rendered fit for the nutrition of the different parts of 

 the body. 



In the human subject, the intestines form a canal, usually 

 six times longer than the body; and although this is but one 

 long circumvoluted tube, the upper portion has the name 

 of small intestines, and the lower of large intestines. In 

 quadrupeds this canal varies considerably in its structure, 

 according to the different kinds of food on which the animals 

 subsist. On this likewise depends its length. In those that 

 are carnivorous it is short, but in the herbivorous and 

 granivorous animals it is generally very long. 



The small intestines are divided by anatomists into three 

 parts, called the duodenum, jejunum, and ileum; and the 

 large into two, called the colon and rectum. At the be- 

 ginning of the colon is a gut, closed at one end, and hence 

 called the ccecum. This appendix to the intestinal canal 

 is generally empty. In dogs, and some other animals, it 

 is very large; but in man, though it is usually ranked 

 among the great intestines, its size is diminutive. 



After the digestion is completed, the alimentary matter is 

 moved through the intestines by the successive contraction 

 of the fibres of their muscular coats, which produces a slow 

 motion, somewhat similar to the crawling of a worm, and 



called 



