120 AGRICULTURE OF MAINE. 



The working parts or the machinery of the body, although 

 containing a great variety of substances, differing but shghtly 

 in chemical composition, may for our purpose be grouped under 

 three heads, — water, ash and protein. Water is rarely less than 

 half and sometimes is three-fourths the entire weight. The 

 proportion is greatest in young or lean animals and decreases as 

 they become more mature or fatter. Ash or mineral matter is 

 the portion left after the animal is burned. Tt is principally in 

 the bones, or framework, but is found in all parts of the body 

 and is just as essential as water. Protein is the name given to a 

 highly important group of substances of which white of egg, 

 lean meat, the casein or curd of milk and the gluten of flour 

 are familiar examples. They are composed of the chemical 

 elements nitrogen, carbon, hydrogen and sulphur. This group 

 of substances differs from others principally in containing nitro- 

 gen, which is an important element in both feeds and fertilizers. 

 Protein is the basis of the living tissues of the body, the so- 

 called protoplasm, and i.s the substance through which life mani- 

 fests itself. Besides the working parts, the body contains 

 a store of reserve materials in the form of fat, which is stored 

 up when food is abimdant and drawn on when food is scarce. 

 The per cent of fat in farm animals varies greatly, seldom going 

 below six per cent, or rising above 30 per cent. In addition to 

 fat the animal also contains a small amount of carbohydrates 

 (sugar) called glycogen. Neither of these substances contain 

 nitrogen. 



TIIIv COMPONENTS OE FEEDING STUFFS. 



The vegetable feeding stuffs which nourish the animal, like 

 it, are made up of a wide variety of substances but for our 

 purpose here may be classified in a few groups which are the 

 same as those found in the animal, namely water, ash, protein, 

 fat anrl carbohydrates. The proportions of these ingredients in 

 the plants are widely different from what they are in the animal 

 kingdom. Protein is the predominant ingredient, aside from 

 water, in animals; also a large amount of reserve force is stored 

 up in fat with a very small amount of carbohydrates. Protein 

 is also present in all j^lants. ])ut the predominating ingredient 



