THE NUTRIENTS AND DIGESTION 311 



an animal starch, is stored in the liver, which converts 

 it into a sugar called glucose, and gives it out to the 

 circulation, from whence it helps to supply energy to 

 the muscles. 



According to Atwater,i carbohydrates form 2.4 per cent, 

 of the total weight of the liver of the young chicken. Lang- 

 worthy* reports that 0.67 per cent, of the egg is carbohydrate, 

 one-third of which occurs in the yolk and two-thirds in the 

 albumen. , 



Fats. — Fat contains the same elements as do the carbohy- 

 drates, but in very different proportions. Perhaps the most 

 characteristic difference is in the proportion of carbon, 

 which is very much greater in the case of fat. The comparison 

 between the percentage composition of starch and stearin, 

 a fat found in both the fowl's body and the egg, is as follows: 



starch 

 Stearin 



Fat is present in nearly all grains, but in very small 

 proportions as compared with the body of the fowl or even 

 the egg. While it forms 5 per cent, of the air-dry weight 

 of corn and oats and 2.1 per cent, of wheat, it constitutes 

 17 per cent, of the live weight of a nervous, active Leghorn 

 hen and 38 per cent, of the dry-matter weight. It comprises 

 8.9 per cent, of the weight of the new-laid egg, all but a trace 

 being located in the yolk, of which it forms 33.3 per cent. 

 The fats in both the egg and the carcass are chiefly palmitin, 

 stearin, and olein. 



Fat stores energy and acts as a non-conductor of heat, 

 the subcutaneous deposits being a very efficient protection 

 against cold. 



Nature's Provision of the Nutrients.' — ^The source of the 

 various nutrients in the rations of wild and domestic birds 

 is as follows: 



» U. S. Farmers' Bulletin No. 182. 



2 Ibid., No. 128. 



'Adapted from a statement of Jaffa, California Bulletin No. 164. 



