T14AN6AGXIOISS OJb' SJiOTION B. 531 



cieiit for the formation of the fat they produced. For simplicity of illustration, and 

 to give every possible advantage to the view that nitrogenous substance might have 

 been the source of the produced fat, we assumed the whole of the crude fat of the 

 food to have been stored up in the animal — thus estimating a minimum amount to 

 be produced. Then, again, we supposed the whole of the nitrogenous substance of 

 the food to be perfectly digested, and to become available for the purposes of the 

 system. Lastly, after deducting the amount of nitrogenous substance estimated to 

 be stored up as such, the whole of the remainder was reckoned to be so broken up 

 that no other carbon-compoimds than fat and urea would be produced. 



The result was, that, even adopting these inadmissible assumptions, in all the 

 cases in which, according to common experience, the food was admittedly the most 

 appropriate for the fattening of the animal, the calculation showed that a large 

 amount of fat had been produced which could not have been derived from the 

 nitrogenous substance of the food, and must therefore have had its source in the 

 carbo-hydrates. Such a result is, moreover, entirely accordant with experience in 

 practical feeding. 



Reviewing the whole subject in great detail in 1869, Professor Voit refers to 

 these results and calculations. He confesses that he has not been able to get a 

 general view of the experiments from the mass of figures recorded, and from his 

 comments he shows that he has on some points misunderstood them. He admits, 

 however, that, as the figures stand, it would appear that fat had, in some instances, 

 been derived from the carbo-hydrates. Still, he says, he cannot allow himself to 

 consider that a transformation of carbo-hydrates into fat has thus been proved. 



Professor Emil von Wolff, again, in his ' Landwirthschaftlicbe Fiitterungslehre,' 

 referring to the same experiments, admits that they are almost incomprehensible 

 unless we assume the direct concurrence of the carbo-hydrates in the formation of 

 fat. He, nevertheless, seems to consider that evidence of the kind in question is 

 inconclusive ; and he suggests that experiments with pigs should be made ui a 

 respiration apparatus to determine the point. 



Mr. Lawes and myself entertained, however, the utmost confidence that the 

 question was of easy settlement without any such apparatus, provided only suit- 

 able animals and suitable foods were selected. I, accordingly, gave a paper on the 

 subject in the /Sferfi'ow yV/r Landwirthschaft-und Acp-icuUur-Chemie, at the Natur- 

 forscher Versammlung held at Hamburg in 1876.^ The points which I particu- 

 larly insisted upon were — that the pig should be the subject of experiment ; that he 

 should be allowed to take as much as he woidd eat of his most appropriate fattening 

 food, so that his increase, and the fat he produced, should bear as large a proportion 

 as possible to his weight, to the total food, and to the total nitrogenous substance 

 consimied. Finally, it was maintained that, if these conditions were observed, and 

 the constituents of the food determined, and those of the increase of the animal 

 estimated according to recognised methods, the results covdd not fail to be perfectly 

 conclusive, without the intervention, either of a respiration apparatus, or of the 

 analysis of the solid and liqiud matters voided. 



Results so obtained were adduced in proof of the correctness of the conclusions 

 arrived at. We at the same time admitted that, although, for reasons indicated, 

 we had always assumed that fat was formed from the carbo-hydrates in the case of 

 ruminants as well as of pigs, yet, as in our experiments with those animals we had 

 supplied too large amoiauts of ready formed fat, or of nitrogenous matter, or of 

 both, it coidd not be shown so conclusively by the same mode of calculation in 

 their case as in that of pigs. 



In the discussion which followed. Professor Henneberg agreed that it seemed 

 probable that fat coidd be formed from the carbo-hydrates in the case of pigs. In 

 the case of experiments with other animals, however, the amount of fat produced 

 was too nearly balanced by the amoimt of fat and albuminous matters available, to 

 afford conclusive evidence on the point. 



Quite recently, Professor Emil von Wolff (' Landwirthschaftlicbe Jahrbiicher,' 



' The substance of that communication is given in the Journal of Anatomy an 

 Phyndlogy, vol. xi. part iv. 



M M 2 



