12 HARRIS Otf THE PIG. 



of which are supposed to take place chiefly after leaving 

 the stomach, and more or less throughout the intestinal 

 canal." 



These facts explain very clearly why an ox or a sheep 

 can thrive on more bulky food than a pig ; also why a pig 

 can assimilate more food than an ox or a sheep, but they 

 do not show why a given amount of food should produce 

 so much more flesh and fat when fed to the pig than when 

 fed to oxen or sheep unless, indeed, we are to suppose 

 that in the case of the ox and the sheep, a considerable 

 proportion of the food passes through the body undigest- 

 ed and unassimilated. But an analysis of the excre- 

 ments indicates nothing of this kind. Except when an 

 excessive amount of grain is allowed, the food is unques- 

 tionably as thoroughly digested and assimilated in the 

 ox and the sheep, as in the pig. 



We must, therefore, look for some other explanation of 

 the fact that pigs can gain more rapidly on a given 

 amount of nutriment than oxen or sheep. 



An animal requires a certain amount of nutritive matter 

 merely to sustain life. This matter may be derived either 

 from the daily food supplied, or from matter previously 

 stored up in the body. The actual amount required, va- 

 ries greatly according to the conditions in which the ani- 

 mal is placed. If kept comfortably warm and quiet, less 

 is required than if exposed to cold, or compelled to labor. 

 But in all cases, wherever life exists, a certain amount of 

 nutritive matter is necessary for its support. Directly or 

 indirectly, this is always derived from the food. 



How much food is necessary to keep an animal so that 

 it shall neither gain nor lose in flesh, has not been accu- 

 rately ascertained. Thousands of animals are so kept, 

 but the actual amount consumed is seldom determined. 

 It often happens that cows, not giving milk, are so kept 

 during the winter that they do not weigh a pound more 

 in the spring than in the fall. We receive absolutely noth- 



