THE SOURCE OF MUSCULAR POWER. 817 



to be insufficient to raise the weight of their bodies to the height of 

 the mountain, and hence they conclude that the lacking energy at least 

 must have been derived from non-nitrogenous materials. 



Their experiments were well designed for the purpose intended, and 

 the criticisms of Professor Flint (pp. 40-43) that the decrease in the 

 excretion of nitrogen during and immediately after the work was due 

 to the abstinence from albuminoid food, and that no comparison of 

 rest with work was made, while doubtless well founded, do not touch the 

 point at issue, viz., that a certain amount of work was performed and 

 a certain amount of proteine destroyed, and that the latter was not, 

 according to their calculations, sufficient to yield the amount of force 

 actually exerted. The only grounds upon which the validity of their 

 results can be successfully disputed are either that the principle of cal- 

 culation employed by them or their data as to the heat of combustion 

 of proteine were erroneous. We shall return to this point later. It 

 may be added, in regard to the experiments of Voit and the other in- 

 vestigators in this field, that they are free from the failings which Pro- 

 fessor Flint finds in those of Fick and Wislicenus, and also of Parkes. 



The experiments of Dr. Parkes, which Professor Flint apparently 

 regards as at least partially sustaining the view which he advocates, 

 show in the great majority of cases either no increase or a slight de- 

 crease of the excretion of nitrogen as a consequence of work, and Dr. 

 Parkes himself expressly says ("Journal of the Royal Society," vol. 

 xix., p. 349) : " The result of both series was, so far, to confirm the 

 experiments, which show that the changes in the nitrogen of the 

 urine . . . are small in extent, and afford no measure of the work." 



Professor Flint's chief reliance, however, seems to be the experi- 

 ments made in 1876 by Dr. Pavy, and published in a series of papers 

 in "The Lancet," and his own experiments made in 1870 ("New York 

 Medical Journal," June, 1871). 



These two series of experiments differ decidedly, both in method 

 and results, from those heretofore mentioned, both of them showing, ac- 

 cording to their authors, an increased elimination of nitrogen through 

 the kidneys as a result of muscular exertion. They were made upon 

 two pedestrians, Perkins and Weston, during the performance of 

 various feats of pedestrianism, and hence under conditions that ex- 

 cluded an exact measurement of the amount of work performed. Un- 

 fortunately, also, they could not, from the nature of the case, be made 

 with that rigorous control of all the conditions of experiment which is 

 essential in such researches ; and they suffer under various sources of 

 inaccuracy which materially lessen their value. 



In the first place, no attempt was made to regulate the diet of the 

 two men ; they ate what and when they chose. In most experiments 

 on this subject it has been considered necessary to employ a perfectly 

 uniform diet as regards nitrogen, and an instructive example of the 

 pains taken to insure it may be found in a paper by Voit and Petten- 



TOL. XT. 52 



