448 Mr. J. B. Lawes and Dr. Gilbert on the Sources 



of the probable error of calculation here indicated is, however, 

 not such as in any degree to throw doubt upon the validity of 

 any conclusions which will be drawn from the indications of 

 the figures as they stand. 



It is seen that, of the determined or estimated total fat stored 

 up in the increase, the proportion which could possibly have 

 been derived from the ready-formed fat of the food, even sup- 

 posing the whole of that supplied had been assimilated, was so 

 small as to leave no doubt whatever that a very large propor- 

 tion of the stored-up fat must have been produced from other 

 constituents than the ready-formed fatty matter of the food. 

 According to the figures given in the Table, the proportion of 

 fat which must have been so produced, ranged from about two- 

 thirds to about eight-ninths of the total amount stored up. 



Assuming it, then, to be established beyond doubt that there 

 was a very large formation of fat within the body from other 

 constituents than the fatty matter of the food, the questions 

 arise, whether this large amount of produced fat could possi- 

 bly have been derived from the nitrogenous constituents of the 

 food ? or whether it must of necessity have had its source, in 

 greater or less proportion, in the carbo-hydrates at the same 

 time supplied ? The results adduced afford conclusive evidence 

 on this point also. 



The figures show that, after deducting from the total amount 

 of nitrogenous substance consumed for the production of 100 lbs. 

 of increase in live-weight the small amount estimated to be 

 stored up in the increase, there remains a very large propor- 

 tion available, it may be, for the production of fat with other 

 products. 



If we next compare the amount of carbon in the estimated 

 produced fat with the amount contained in the nitrogenous sub- 

 stance of the food not stored up as increase, minus that con- 

 tained in the urea which would be one of the final products of 

 the breaking up of this nitrogenous substance (or its equiva- 

 lent given off), the result shows in some cases an excess, and in 

 others a deficiency, of carbon possibly available from the nitro- 

 genous constituents of the food, compared with that required for 

 the formation of the fat estimated to be derived from other 

 constituents than the ready-formed fat in the food. 



Reckoned to the standard of 100 carbon in the estimated 

 produced fat, it is seen, as shown in the two bottom lines of 

 the Table, that in Exps. 1, 2 & 3, in which the proportion 

 of non-nitrogenous to nitrogenous substance in the food was 

 (especially in Exp. 3) considerably less than in such food as 

 experience has shown to be the most appropriate in the fatten- 

 ing of the pig — that is to say, in which the nitrogenous sub- 





