110 



THE CHEMISTRY OF THE FARM 



sheep, and pigs, when passing from the " store " to the 

 " fat " condition has been calculated by Lawes and 

 Gilbert with the following results : — 



PERCENTAGE COMPOSITION OF THE INCREASE WHILST 

 FATTENING. 



The increase during the fattening stage of growth is 

 seen to contain eight to nine parts of fat for one of 

 nitrogenous matter. The proportion of fat would be 

 somewhat greater still in the increase of highly fattened 

 animals, as, for instance, of pigs fed for bacon. 



The Processes of Nutrition.— We have already seen 

 that the food of plants is of the simplest character. 

 From such simple substances as carbonic acid, nitric 

 acid, water, and a few salts, a plant is able to construct 

 a great variety of elaborate compounds. It accom- 

 plishes these surprising transformations by a consump- 

 tion of energy (sunlight) external to itself. An animal 

 has no such constructive power. The animal frame 

 is built up of substances existing ready formed in the 

 ;ood, or produced by the splitting up or partial com- 

 ' ustion of some of the food constituents in the body. 

 The animal derives no aid from external energy. The 



