150 SWINE 



not use the excess over and above this quantity as 

 economically for producing gains in live weight as when 

 fed a quantity below this amount. The portion that is 

 lost on account of this less economical use is what is 

 called the factor of waste. When an animal is once put 

 under such conditions, the habit of wasting apparently is 

 more or less permanently established. 



On account of the tendency of the animal body to estab- 

 lish nitrogen equilibrium there is a constantly increasing 

 quantity of crude protein wasted (excreted without hav- 

 ing served any purpose in the body whatever). This also 

 consumes considerable energy and possibly causes physio- 

 logical disturbances which, together with the cabohy- 

 drate and ether extract that may also be wasted, along 

 with the crude protein, makes up the factor of waste 

 represented in the drawing by G E. It will be no- 

 ticed that at the point when the pigs were 33 weeks old, 

 the feed used for maintenance plus the feed used to sup- 

 ply the factor of waste is equal to the total amount of 

 feed eaten. This left no feed to be used for putting on 

 flesh and fat and the result was that the pigs made no 

 gains in live weight at this time. They remained sta- 

 tionary throughout the period of one week. This is a 

 point where nitrogen equilibrium (an equality between 

 the amounts coming in and going out) probably was 

 either established, or exceeded. 



It is supposed that at birth the factor of waste is ab- 

 sent or at least at the lowest possible point and that in 

 this experiment it was constantly increased up to the 

 point H. But if the facts of the case were known, as al- 

 ready indicated, it is probable, and very likely, that the 

 curve G H would run at a higher level than is here rep- 

 resented, and that it had reached its highest point some- 



