TBANSACTIONS OF SECTION B. 53 



whicli has been assumed to be correct by so many writers, even up to the present 

 time, did not bold good— namely, tliat ' The sum of the mechanical effects pro- 

 duced in two indi\-iduals, in the same temperature, is proportional to the amount of 

 nitrogen in their urine ; whether the mechanical force has been employed in ^olun- 

 tary or involuntary motions, whether it has been consumed by the limbs nr by tlie 

 heart and other viscera ' — unless, indeed, as has been assumed by some experi- 

 menters, there is, with increased nitrogen in the food, an increased amount of 

 mechanical force employed in the ' involuntary motions ' sufficient to account for 

 the increased amount of urea voided. 



The question remained in this condition until 1860, when Bischoff and Voit 

 published the results of a long series of experiments made with a dog. They found 

 that, even when the animal was kept at rest, the amount of urea voided varied 

 closely in proportion to the variation in the amount of nitrogenous substance 

 given'in the food — a fact whicli they explained on the assumption tliat there must 

 have been a corresponding increase in the force exercised in the conduct of the 

 actions proceeding within the body itself in connection with the disposal of the 

 increased amount of nitrogeneous substance consumed. Subsequently, however, 

 they found that the amount of urea passed by the animal was, -\\ath equal condi- 

 tions as to food, &c., no greater when he was subjected to labour than when at 

 rest ; whilst, on the other hand, the carbonic acid evolved was much increased 

 bv such exercise. They accordingly somewhat modified their views. 



In 1866 appeared a paper by Professors Fick and Wislicenus, giving tlie results 

 obtained in a mountain ascent. 'They found that practically the amount of urea 

 voided was scarcely increased by the labour thus undertaken. Professor Frankland 

 gave an account of these experiments in a lecture at the Royal Institution in the 

 same year ; and he subsequently followed up the subject by an investigation of the 

 heat de^•eloped in the combustion of various articles of food, applying the results in 

 illustration of the phenomena of the exercise of force. 



Lastly, KeUner has made some very interesting experiments with a horse at 

 Hohenhe'im, the results of which were published last year. In one series, tlie ex- 

 periment was divided into five periods, the same food being given throughout ; but 

 the animal accomplished different distances, and drew different weights, the draught 

 being measured by a horse-dynamometer. The changes in live-weight, the amount 

 of water drunk-, the temperature, the amount of matters voided, and their contents 

 in nitrogen, were also determined. 



The result was, tliat with oidy moderate labour there was no marked increase 

 in the nitrogen eliminated in the urine, but that with excessive labour the animal 

 lost weight and eliminated more nitrogen. Kellner concluded, accordingly, that, 

 under certain circumstances, muscular action can increase the transformation ^ of 

 albumin in the organism in a direct way ; but that, nevertheless, in the first line 

 is the oxidation of the non-nitrogenous matters — carbo-hydrates and fat, next comes 

 in requisition the circulation-albumin, and finally the organ-albumin is attacked. 



In reference to these conclusions from the most recent experiments relating^ to 

 the subject, we may wind up this brief historical sketch of the changes of view- 

 respecting it, with, the following quotation from our own paper published in 

 1866 : • — ' ... all the evidence at command tended to show that by an increased 

 exercise of muscidar power there was, with increased requirement for respirable 

 material, probably no increased production and voidance of urea, unless, owng to 

 excess of nitrogenous matter in the food, or a deficiency of available non-nitrogenous 

 substance, or diseased action, the nitrogenous constituents of the fluids or solids of 

 the body were drawn upon in an abnormal degree for the supply of respirable 

 material.' 



In conclusion, although I fully agree with Voit, Zuntz, Wolff, and others, that 

 there stiU remains much for both Chemistry and Physiology to settle iu connection 

 with these two questions of * The Sources of the Fat of the Animal Bodij ' and ' The 

 Origin of Muscidar Fower,' yet I think we may congratulate ourselves on the re- 

 establishment of the true faith in regard to them, so far at least as the most im- 

 portant practical points are concerned. 



" 'Food in its relation to various exigencies of the animal body.' — PJiil. j)fafj., July 

 18GC. 



