WHAT IS A HOG? 119 



ately more water than a hog that is very fat or in prime 

 condition for market. Generally speaking, hogs with this 

 degree of variation will contain from 42 to 58 per cent 

 of water. In order to have a hog develop to the best pos- 

 sible advantage, he must have sufficient water to supply 

 this amount, and besides he must also have water for the 

 general working of his internal mechanism. The latter is 

 of the greater importance. Water is very essential in the 

 excretion of waste products, such as the waste nitrogen 

 resulting from the protein metabolism which is excreted 

 as a part of the urine. As to the distribution of water in 

 the body, it is found everywhere, but more extensively 

 in the softer tissues; the hard tissues such as the bone 

 containing a relatively smaller quantity. 



PROTEIN. 



The vital or working parts of an animal body are com- 

 posed principally of protein. Thus it is seen that as long 

 as an animal lives and works it needs protein not only to 

 build up new tissue during the growing period, but also 

 to maintain the protein metabolism* during idleness and 

 during periods of work. Peculiarly as long as the animal 

 lives this part of his mechanism is working all the time, 

 and as far as experimental data show, he needs as much 

 protein when he is at rest as when he is at work, show- 

 ing that the mechanical work an animal does is done at 

 the expense of nutrients other than protein, consequently 

 carbohydrate and fat. Since the latter nutrient is found 

 in feed stuffs only in limited quantities, and since also 

 his internal mechanism can handle only a limited quan- 



*Metabolism means the process involved in the changes that 

 food substances undergo in the animal body after they are digested 

 and taken into the system. This is similar in part to what is 

 meant by assimilation. 



