THE NUTRIENTS AND DIGESTION 309 



called "protein," a term adapted from the Greek word 

 meaning "to be first." Besides nitrogen, protein compounds 

 always contain carbon, hydrogen, and oxygen, and some- 

 times contain sulphur, phosphorus, and iron. 



As will be seen by referring to Table XXVII, over 21 per 

 cent, of the entire body of a Leghorn hen is protein, while it 

 constitutes 48.9 per cent, or nearly half of the total dry 

 matter. While it forms but 12.83 per cent, of the new-laid 

 egg because of the large amount of water and ash, it will 

 be noticed that it constitutes 49.8 per cent, of the dry matter 

 of the contents of the egg. 



In the fowl's body the muscles, skin, feathers, tendons, 

 brain, blood, and internal organs are composed mainly of 

 protein. The dry matter of the white of the egg is nearly 

 94 per cent, protein, while that of the yolk is over 34 per cent, 

 protein. 



Egg albumen shows very nicely some of the characteristics 

 of protein compounds. In analysis it approaches very closely 

 the average analysis of proteins as given by Sherman:' 



Carbon, Hydrogen, Oxygen, Nitrogen, Sulphur, 

 per cent per cent. per cent. per cent, per cent. 



1.000 

 1.616 



Average analysis of proteins 53.00 7.00 23.000 16.00 

 Analysis of egg albumen 52 . 75 7.10 23 . 024 15 . 51 



When dry it forms a horny substance which melts in the 

 flame, forming a black mass. At the same time fumes are 

 given off, which smell like burning hair or feathers. When in 

 solution proteins display a mucilaginous character which is 

 made use of in the commercial glues and mucilages. 



The most familiar example of a vegetable protein is the 

 gluten of wheat. The protein content of wheat averages a 

 little less than 12 per cent, and of corn a little over 10 per 

 cent. Most of the common whole grains depart very little 

 from these figures. While some of the grain by-products such 

 as wheat middlings (17.8 per cent.) and gluten feed (25.4 per 



' Chemistry of Food and Nutrition. 



