72 GRAMINIVORA REQUIRE 



from which their blood is formed, strictly speaking, only 

 a certain excess of carbon, which the animal organism 

 cannot possibly employ to produce fibrine or albumen, 

 because the nitrogenized constituents of the food al- 

 ready contain the carbon necessary for the production 

 of blood, and because the blood in the body of the 

 carnivora is formed without the aid of this excess of 

 carbon. 



The function performed in the vital process of the 

 graminivora by these substances (sugar, gum, &c.) is 

 indicated in a very clear and convincing manner, when 

 we take into consideration the very small relative 

 amount of the carbon which these animals consume in 

 the nitrogenized constituents of their food, which bears 

 no proportion whatever to the oxygen absorbed through 

 the skin and lungs. 



A horse, for example, can be kept in perfectly good 

 condition, if he obtain as food 15 Ibs. of hay and 4J 

 Ibs. of oats, daily. If we now calculate the whole 

 amount of nitrogen in these matters, as ascertained by 

 analysis (1-5 per cent, in the hay, 2'2 per cent, in the 

 oats), (is) in the form of blood, that is, as fibrine and 

 albumen, with the due proportion of water in blood 

 (80 per cent.), the horse receives daily no more than 

 4 1 oz. of nitrogen, corresponding to about 8 Ibs. of 

 blood. But along with this nitrogen, that is, combined 

 with it in the form of fibrine or albumen, the animal 

 receives only about 14 J oz. of carbon. Only about 

 8 oz. of this can be employed to support respiration, 

 for with the nitrogen expelled in the urine there are 



