84 AMERICAN MANURES. 



food containing a large amount of carbon, and a 

 small amount of nitrogen, and allowing them 

 but little exercise, the increase of fat can be 

 controlled at pleasure. 



Woody Fibre is rich in carbon, but it is*not in 

 a form to be readily assimilated on account of its 

 insolubility. For this reason, the carbon con- 

 tained in wheat, in corn, and in potatoes, in the 

 form of starch and gum, is the principal source 

 of supply for man. Woody fibre can be changed 

 to starch and sugar in the laboratory of the 

 chemist, but the digestive organs of men and 

 animals are inadequate to the production of this 

 result ; otherwise, animals might be fattened on 

 saw-dust or pine shavings. 



The process of fattening depends upon the 

 fact, that too small an amount of oxygen is 

 taken into the system by respiration to consume 

 the carbon in the food, the unconsumed part 

 being in such case changed into fat. Hence it 

 is, that animals at rest, or taking but little 

 exercise, if fed upon food containing much starch 

 or gum, fatten rapidly ; because then respiration 

 being less frequent and full, too small an amount 

 of oxygen is taken into the lungs to consume the 

 carbon. The foregoing Table also furnishes in- 

 formation as to the relative value of the several 

 grasses and grains named for fattening. 



