422 MANUAL OF PHYSIOLOGY. 



accompanied by a decrease in the weight of the animal, and an 

 increase causes it to put on flesh. For each new body weight 

 there is a new nitrogenous equilibrium, which is only obtained 

 after the disturbed relation between the nitrogenous ingesta and 

 excreta has been readjusted. 



The increase of weight which follows a liberal meat diet depends 

 in a great measure on fat being stored up in the body. Much 

 more of this material is made than could come from the fat taken 

 with the meat ; hence, we must conclude that it is made from 

 the albuminous parts of the meat. 



The effect of a diet without any albuminous food is that the 

 animal dies of starvation nearly as soon as if deprived of all 

 forms of food, with the exception that the weight of the body is 

 much less reduced at the time of death. 



The addition of fats and sugars to meat diet allows a consider- 

 able reduction to be made in the supply of meat, and both the 

 body weight and nitrogenous tissue change can be kept in equi- 

 librium on a smaller amount of food. It has been estimated that 

 the nitrogenous tissue change is reduced 7 per cent, by the addi- 

 tion of fat, and 10 per cent, by the addition of carbohydrate food 

 to the meat diet ; therefore less meat is wanted to make up nitro- 

 genous tissues. Further, fats and sugars, which obviously cannot 

 of themselves form an adequate diet, since they contain no nitro- 

 gen, seem to have the power of accomplishing some end in the 

 economy which, in their absence, requires a considerable expen- 

 diture of nitrogenous materials to bring about. Fats and sugars, 

 then, supply to the body readily oxidizable materials, and thus 

 shield the albuminous tissues from oxidation, as well as reduce 

 absolutely the nitrogenous metabolism. 



It would further appear from the experience gained from the 

 stall feeding of animals that a good supply of carbohydrates, 

 together with a limited quantity of nitrogenous food, is admirably 

 adapted to produce fat. Since much more fat has been found to 

 be produced in pigs than could be accounted for by the albu- 

 minous and fatty constituents of their diet, we must suppose that 

 from their carbohydrated food fat can be manufactured in their 

 body. 



