252 STATE BOARD OF AGRICULTURE. 



would be left were all the water dried out of them. In the comparison 

 of stock foods, then, the only fair basis is the dry matter which they con- 

 tain. i$| 



The meaning of the word protein is a little harder to illustrate. A ref- 

 erence to the diet of human beings may aid in making its significance 

 clear. No dinner seems complete without some kind of meat. Lean meat 

 contains in the first place a large amount of water. If this were driven 

 off, the drv matter would be found to consist of the red muscle, fat and a 

 small amount of connective tissue. It is the red muscular tissue that 

 is the characteristic constituent of lean meat. If meat is w T anting, the 

 house wife finds it possible to supply its place with eggs. One hundred 

 pounds of eggs contain not far from sixty-six pounds of water, 9.5 pounds 

 of fat and 13 pounds of albumen, a material having a chemical com- 

 position very similar if not identical with that of the dry, red muscle of 

 lean meat. If eggs were not obtainable as a substitute for meat, 

 its place might be acceptably filled by a sufficient quantity of 

 cheese. One hundred pounds of Cheddar cheese contain 35.6 pounds 

 of water, 32 pounds of fat and 28.2 pounds of casein, a substance 

 having also a chemical composition very similar to that of the dry lean 

 muscle of lean meat. Now this class of substances to which belong dry 

 lean meat, the albumen of the white of eggs, and the casein of cheese, 

 is called protein. 



All of our cattle foods contain compounds having a composition similar 

 to the protein of lean meat, eggs and cheese and serving for our domestic 

 animals the same purpose that the protein of meat, cheese and eggs does 

 for human beings. 



It must not be understood that meat and eggs and cheese are the only 

 articles of human diet that furnish protein. The truth is far otherwise. 

 While meat and some animal products have a larger proportion of protein 

 than do most vegetables, the latter are by no means wanting in it. Even 

 potatoes, a very starchy food, contain, when boiled, on the average, 2.7 

 pounds of protein for every hundred pounds of gross weight. Beans 

 have a much larger per cent of protein, on the average 21.81 pounds to 

 the hundred weight. White bread contains 9.5 per cent of this valuable 

 nutrient. The limited number of experiments that have been tried on 

 this point lead us to believe that a pound of protein derived from potatoes 

 is equally as valuable as the same amount derived from lean meat, 

 though this point has not been well established. 



Turning now to cattle foods, there are some of them that may be sup- 

 posed to be related to the appetite of the cow in the same way that eggs, 

 cheese and meat are to the appetite of men. To this class of cattle foods 

 would belong such materials as cotton seed meal, linseed meal, buck- 

 wheat middlings, and possibly wheat bran and middlings. One hundred 

 pounds of cotton seed meal contain 42.4 pounds of protein while the same 

 weight of cheese would have but 28.2 pounds. Linseed meal, old process, 

 has in each hundred pounds :;2.9 pounds of protein while eggs, the typical 

 proteid substance of the human dietary, contains but 13.1 pounds of 

 protein per hundred weight. Men eat eggs and meat because the protein 

 they contain satisfies hunger for that ingredient. So the appetite of the 

 cow calls for materials containing protein and is satisfied when fed on re- 

 latively small quantities of feeding stuffs of this class rich in protein. 



