74 YALE AGRICULTURAL LECTURES. 



food out of naturally growing grasses, and employ hundreds 

 of otherwise refuse matters for the same object. A diagram 

 exhibited by the lecturer showed the composition of a pig when 

 fat and lean, thus : 



Fat Per Cent. Lean Per Cent. 



Water 45 60 



Albuminoids 15 17 



Fat .' 37 21 



Mineral matter, or ash 3 2 



Total 100 100 



The carbo-hydrates starch, sugar, cellulose, gum, &c. are 

 changed by the animal into grape sugar, and are then ready to 

 be assimilated to build up its body. The grape sugar is chang 

 ed into lactic and butyric acids, and thence into fat. The mine 

 ral matters found in the bones, blood, and other portions of 

 the body, are of course obtained from the plants, which in their 

 turn suck them from the soil. In some districts, such as that 

 about Leipsic, some of these necessary minerals are deficient in 

 the soil ; and it has often been observed, that where phosphate 

 of lime is not in the farm soil in sufficient quantity, cows suffer 

 from bone disease, and will gnaw any old bone that they may 

 find lying on the ground. Animal force and heat, like steam, 

 are generated by the actual combustion of material ; in the 

 former cases this being food, in the latter fuel. The "fire 

 place" in the animal is all over its body, wherever a pin-prick 

 will draw blood. As in the steam engine, the amount of mus 

 cular and nervous force in the animal is proportionate to the 

 amount of fuel or food consumed. First, material is stored up 

 in the tissues for use, and then every exertion of the muscles 

 or brain is accompanied by an oxydation, or burning of the 

 tissues. In this process, carbonic acid, water, and a small 

 quantity of ammonia, are given off the remainder of the am 

 monia being transformed into urea, and voided from the body. 

 An engine is merely a mechanism for using an engendered 

 force, but the animal is itself consumed, and must be renewed 



