296 Royal Society .— 



about 9 parts of dry increase, In sheep liberally feci on corn or oil- 

 cake and succulent roots, for 100 of dry food consumed, about 8 

 parts were non-nitrogenous substance, that is, fat. There was there- 

 fore only about 1 part stored as nitrogenous and mineral matters 

 taken together. The average of the estimates showed the produce 

 of 100 of the collective dry substance of the consumed food of sheep 

 to be — about, 0'2 part of mineral matter, 0'8 part nitrogenous 

 compounds, and 8 parts fat, stored up ; leaving therefore about 9 1 

 parts to be expired, perspired, or voided. 



Taking the average of all the estimates of this kind relating to 

 piffs — of the 17^ parts of dry increase for 100 of dry matter of food 

 consumed, about 15j parts were estimated as fat, rather more than 

 l|^rd part nitrogenous substance, and an insignificant amount as 

 mineral matter. On this plan of calculation, therefore, there would 

 appear to be, in the case of fattening pigs, only from 82 to 83 parts 

 of food-constituents expired, perspired, or voided, for 100 of the 

 collective dry substance of food consumed. 



It is obvious that the ultimate composition of the dry substance 

 of increase must be very diiferent from that of the 1 00 of dry sub- 

 stance consumed. This is strikingly illustrated in the case of the 

 fat. In most of the experiments with pigs, the fatty matter in the 

 food was determined. On the average of the cases it amounted to 

 less than -^-th as much as was estimated to be stored up in the in- 

 crease of the animals. There was obviously therefore a formation 

 of fat in the body from some other constituent or constituents of the 

 food. Supposing the |^ths or more of the stored-up fat which must 

 have been formed in the body to have been produced from starch, 

 it was estimated that it would require 2^ parts of starch to contri- 

 bute 1 part of produced fat. Accordingly, it would appear that a 

 much larger proportion of the consumed dry matter is, as it were, 

 directly engaged in the production of the dry fatty increase, than is 

 represented by the amount of the dry increase itself. 



Thus, taking the average of the cases in which the fatty matter 

 in the food of the pigs was determined, it was estimated that 17'4 

 parts of dry increase were produced for 100 of dry matter of food 

 consumed. Of the 17'4 parts of dry increase, lG-04 are reckoned 

 as fat. But there were only 3*96 parts of readj^-formed fatty matter 

 supplied in the food. At least 12"08 parts of fat must therefore 

 have been produced from other substances. If from starch, it would 

 require (at the rate of 2^ parts of starch to 1 of fat) 30 '2 parts of 

 that substance for the formation of the 12'08 parts of produced 

 fat. The ready-formed fat and the starch, together, thus supposed 

 to contribute to the 16'04 parts of fat in the increase, would amount 

 to 34" 16 parts out of the 100 of dry matter of food consumed. But 

 there were, further, 1'36 part of nitrogenous and mineral matters 

 stored up in the increase. In all, therefore, 35*52 parts out of the 

 100 of gross dry matter consumed, contributed, in this compara- 

 tively direct manner, to the production of the 17*4 parts of gross 

 dry increase. 



According to the illustration just given, it appears that there was 



