ELIMINATION OF NITROGEN. 379 



all observations with regard to the influence of muscular exercise upon the 

 elimination of nitrogen, account should be taken of the influence of diet ; and 

 those observations are most valuable which have given the proportion of nitro- 

 gen eliminated to the nitrogen of food. The observations of Fick and Wisli- 

 cenus (1866) showed a diminution in the elimination of nitrogen during work ; 

 but during the time of the muscular work, no nitrogenized food was taken. 

 The same conditions obtained in certain of the observations of Parkes. In 

 a series of observations made in 1870 (Flint), on a person who walked 317 

 miles (about 510 kilometres) in five consecutive days, the diet was normal, 

 and the proportionate quantity of nitrogen was calculated for three periods of 

 five days each, with the following results : 



For the five days before the walk, with an average exercise of about eight 

 miles (13 kilometres) daily, the nitrogen eliminated was 92*82 parts for 100 

 parts of nitrogen ingested. For the five days of the walk, for every hundred 

 parts of nitrogen ingested, there were discharged 153-99 parts. For the five 

 days after the walk, when there was hardly any exercise, for every hundred 

 parts of nitrogen ingested, there were discharged 84*63 parts. During the 

 walk, the nitrogen excreted was in direct ratio to the amount of work ; 

 and the excess of nitrogen eliminated, over the nitrogen of food, almost ex- 

 actly corresponded with a calculation of the nitrogen of the muscular tissue 

 consumed, as estimated from the loss of weight of the body. In 1876, a similar 

 series of observations was made upon the same person by Pavy. In these ob- 

 servations, the subject of the experiment walked 450 miles (724'21 kilometres) 

 in six consecutive days. During this period, the proportionate elimination of 

 nitrogen was increased, but not to the extent observed in 1870. Similar re- 

 sults, although the experiments were made on a less extended scale, were ob- 

 tained by North, in 1878. These results are opposed to the views of many 

 physiologists, since the experiments of Fick and Wislicenus, who regard the 

 elimination of nitrogen under ordinary conditions as dependent mainly upon 

 the diet and not upon the muscular work performed. The observations of 

 Voit, indeed, are favorable to this view. 



Notwithstanding the results obtained by Fick and Wislicenus, Frankland, 

 Haughton, Voit and others, the fact remains that excessively severe and 

 prolonged muscular work increases the elimination of nitrogen over and 

 above the quantity to be accounted for by the nitrogenized food taken. Ac- 

 tual observations (Flint, Pavy and others) are conclusive as regards this 

 simple fact ; but it is well known that muscular exercise largely increases 

 the elimination of carbon dioxide and the consumption of oxygen. In exer- 

 cise so violent as to produce dyspnoea, the distress in breathing is probably 

 due to the impossibility of supplying by the lungs sufficient oxygen to meet 

 the increased demand on the part of the muscular system, and the possible 

 amount of muscular work is thereby limited. 



The observations and conclusions of Oppenheim (1880) go far to harmon- 

 ize the results obtained by different experimenters. Oppenheim concludes 

 that muscular work, when not carried to the extent of producing shortness of 

 breath or when moderate and extending over a considerable length of time, 



