author's method of feeding 153 



hundred pounds live weight, to supply its normal prptein 

 metabolism, and is getting .6 pound in its ration, it will 

 be able to use for storing up in its body .5 pound, pro- 

 vided there is no waste. Obviously, however, this does 

 not necessarily make .5 pound of protein tissue in the 

 body. This is comparable to the bank account in the 

 illustration used. However, on account of the tendency 

 of the animal body, under prevailing conditions to estab- 

 lish nitrogen equilibrium, this .5 pound that at first was 

 used to increase the store of protein and thereby add to 

 the live weight of the pig, will gradually be decreased. 

 After feeding this constant quantity of .6 pound for some 

 time there will be a tendency to establish nitrogen equili- 

 brium so that the animal will be excreting as much pro- 

 tein as is eaten without storing any of it in its body. In 

 order to further increase the store of protein in the body, 

 it is necessary to increase the amount of feed exactly 

 similar to the increase in the salary of the man in the 

 illustration given. 



Suppose now that the pig has come to a point of nitro- 

 gen equilibrium by eating .6 pdund of protein per hun- 

 dred pounds live weight daily. As it gets older the pig 

 normally eats a smaller quantity of feed per hundred 

 pounds live weight daily, which naturally also decreases 

 its protein supply. In order to show what will take place 

 under these conditions, the case already used as an argu- 

 ment will again be taken up at the point at which it was 

 left, namely, granting that the young man has come to a 

 monetary equilibrium when he is receiving a salary of 

 $100 per month. If now his salary is cut down to $75 per 

 month, what will take place? The man, having become 

 accustomed to living at the rate of $100 per month, will, 

 on this reduced salary, at least for some time, draw iipon 



