450 On the Sources of the Fat of the Animal Body. 



nitrogenous constituents supplied was the more nearly that 

 occurring in the admittedly most appropriate fattening food of 

 the animal, the proportion of the fat which must necessarily 

 have been derived from the carbo-hydrates was very large, even 

 allowing all that was possible to have been produced from the 

 nitrogenous substance of the food. 



That, nevertheless, fat may be produced in the animal body 

 at the expense of nitrogenous substance, in greater or less 

 degree according to the character of the animal and of the food, 

 not only chemical and physiological considerations, but direct 

 experimental evidence would lead us to conclude. Indeed we 

 have, in former papers already referred to, called attention to the 

 fact that the results of our experiments with fattening animals, 

 when carefully considered, afford evidence in favour of such a 

 conclusion. To discuss the point satisfactorily on the present 

 occasion, by the aid of figures, would, however, unduly extend 

 the limits of our paper. 



But, as indicating the bearing of the results referred to, it 

 may be stated, in passing, that in numerous cases, otherwise 

 comparable, but in which the amount and proportion of the 

 nitrogenous constituents consumed varied very greatly, the 

 results clearly showed that neither the amount of food con- 

 sumed, nor the amount of increase in live-weight produced, 

 bore any direct relation to the amount of nitrogenous substance 

 supplied. On the other hand, both the amount of food con- 

 sumed and the amount of increase produced bore a very close 

 relation to the supply of digestible non-nitrogenous consti- 

 tuents, and even a closer relation still to the amount of total 

 digestible dry organic substance (that is, nitrogenous and non- 

 nitrogenous taken together) ; whilst, so far as could be judged 

 from careful observation, the proportion of nitrogenous to non- 

 nitrogenous substance (fat) in the increase did not vary in any- 

 thing like a corresponding degree with the variation in the pro- 

 portion of the nitrogenous and non-nitrogenous constituents in 

 the food. The animals consuming excessive amounts of nitro- 

 genous substance did, indeed, show a greater tendency to in- 

 crease in frame and flesh; but they nevertheless became fat. 

 It would appear that the excess of nitrogenous substance had 

 acted vicariously in defect of a greater supply of the non-nitro- 

 genous constituents, contributing material not only to meet the 

 respiratory exigencies of the animal, but also for the production 

 of fat. 



The main conclusions in regard to the sources of the fat of the 

 animal body to which the evidence adduced has led, may be 

 briefly stated as follows : — 



1. That certainly a large proportion of the fat of the Herbi- 



