CHEMISTRY OF THE FEEDINQ OF ANIMALS. 187 



nitrogenous substance, red non-nitrogenous substance, and green 

 total dry organic matter (nitrogenous and non-nitrogenous to- 

 gether), the diagram is constructed as follows : — The smallest 

 quantity of nitrogenous, or non-nitrogenous, or total organic 

 matter consumed in any one experiment is reckoned as 100 ; and 

 the several lines above the base line, which is marked 100, indi- 

 cate larger amounts, corresiDonding to the figures given at the 

 side of the diagram. 



The upper portion shows the relative amounts of each constitu- 

 ent consumed in each experiment per 100 lbs. live weight per 

 week ; that is to say, by a given weight of animal within a given 

 time. A glance shows you that the height to which the colors 

 representing the non-nitrogenous, or the total organic substance 

 reach is very much more uniform than that indicating the con- 

 sumption of nitrogenous substance. In fact, it is perfectly clear 

 that the animals were guided in the amount of food which they 

 consumed by the amount of non-nitrogenous, and not by that of 

 the nitrogenous constituents which it supplied. 



But, according to current theories, the amount of nitrogenous 

 substance ought at least to determine the amount of increase pro- 

 duced. The lower portion of the diagram shows what the animals 

 have to say on this point. The arrangement is the same as before ; 

 but the results show, not how much of each class of constituents 

 was consumed by a given weight of animal within a given time, 

 but how much was consumed to produce a given weight (100 lbs.) 

 of increase. 



Here again we see that the amount of either non-nitrogenous 

 or total organic substance consumed varied comparatively little, 

 whilst that of the nitrogenous su'bstance consumed for the pro- 

 duction of a given amount of increase varied from 100 to over 300 

 parts. 



It is obvious, therefore, that both the amount of food consumed 

 by a given weight of animal within a given time, and that required 

 to produce a given weight of increase, were determined by the 

 amount of available non-nitrogenous substance which the food 

 supplied. The quantities reciuired would, doubtless, have varied 

 within even narrower limits, had all the foods contained equal pro- 

 portions of indigestible woody matter. 



It may be observed that it is doubtful whether pigs are able to 

 digest cellulose, or woody fibre, at all; but there is no doubt, as 

 the investigations of ourselves and others on the point sufiiciently 



