342 EXCRETION 



diet being regular, seem to retard the process of katabolism ; or at least 

 they diminish, in a marked manner, the quantity of matters excreted, 

 particularly urea. Alcohol has a decided influence of this kind. Its 

 action may be modified by the presence of salts and, other matters in dif- 

 ferent alcoholic beverages, but in nearly all direct experiments, alcohol 

 either taken under normal conditions of diet, when the diet is deficient 

 or when it is in excess, diminishes the excretion of urea. The same may 

 be stated in general terms of tea and coffee. 



Influence of Muscular Exercise on the Elimination of Nitrogen. In 

 all observations on the influence of muscular exercise on the elimi- 

 nation of nitrogen, account should be taken of the influence of diet ; 

 and those observations are most valuable which have given the propor- 

 tion of nitrogen eliminated to the nitrogen of food. The observations 

 of Fick and Wislicenus (1866) showed a diminution in the elimination of 

 nitrogen during work ; but during the time of the muscular work, no 

 nitrogenous food was taken. The same conditions obtained in certain 

 of the observations of Parkes. In a series of observations made in 1880 

 (Flint), on a man who walked 317^ miles (about 510 kilometers) 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 fol- 

 lowing results : 



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

 about eight miles (13 kilometers) 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 

 1 5 3. 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 exactly corresponded to 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 on the same man by Pavy. In these observations he walked 450 

 miles (724.2 1 kilometers) in six consecutive days. During this period 

 the proportionate elimination of nitrogen was increased, but not to the 

 extent observed in 1870. Similar results although the experiments 

 were made on a less extended scale were obtained by North in 1878. 

 These observations are opposed to the views of many physiologists, 

 since the experiments of Fick and Wislicenus, who regard the elimina- 

 tion of nitrogen under ordinary conditions as dependent mainly on the 

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

 Voit, indeed, are favorable to this view. 



