350 



Dr. Parkes — Further Experiments on the [Mar. 2, 



1. There was an increased, though slight, outflow of nitrogen after work. 



2. There was apparently a slight lessening of the outflow during work, 

 not dependent on diminution in the amount of urinary water. In the state 

 of rest also, when the diet was equal, there was no lessening, but a slight 

 excess, in the excretion of nitrogen as compared with a period both of 

 forced and ordinary exercise. 



Professor Karl Voit, of Munich, who has a worldwide reputation for his 

 numerous and important contributions to this subject, and who denies that 

 exercise produces any change in the nitrogen, has taken exception to some 

 of these experiments, on the ground more particularly that the daily ingress 

 of nitrogen could not have been kept sufficiently stable. I believe the ex- 

 periments, showing as they do in two men a remarkable agreement in the 

 amount of nitrogen eliminated, and the fact that the two great articles of 

 diet by which nitrogen enters (meat and bread) were selected and weighed 

 with great care* and from the analyses appeared to be of constant compo- 

 sition, prove that the alterations in the daily inflow of nitrogen must have 

 been very small and less than those of the outflow. 



Undoubtedly, however, to insure an absolute uniformity in the entrance 

 of nitrogen in men, is a very difficult matter as long as only ordinary diet 

 is given. The employment of prepared or concentrated food, on the other 

 hand, cannot be considered as good as common diet for such experiments ; 

 for the body is unaccustomed to the particular form in which the food is 

 given. 



It was determined to repeat the experiments in two or three ways. First, 

 not only to use ordinary diet with the usual attention to keep it as uniform 

 as possible from day to day, but to select hours for rest and exercise when 

 the influence of diet is least perceptible, viz. twelve or fourteen hours after 

 food ; then in a second series to use prepared food in which the amount 

 of nitrogen is absolutely constant ; and thirdly to use a diet without 

 nitrogen. 



Unfortunately the experiments on preserved food failed on account of 

 the health breaking down in a few days and before any exercise could be 

 taken. On the ordinary diet also an unexpected difficulty arose, but still 

 the results are worthy of record. The experiments on the non-nitrogenous 

 diet are confirmatory of the former results, as far as the increased elimi- 

 nation after exercise is concerned. 



As the details of the experiments would occupy too much space, I have 

 given only mean numbers when these were sufficient to fairly show the 

 results, and have omitted all details of the chloride of sodium, free acidity 

 of the urine, and other matters. 



The subject of the experiments was T. C, a perfectly healthy soldier 



* The meat was beefsteak, and was selected free from visible fat, and was always 

 cooked in the same way, i. e. fried. The bread was the hospital bread, made daily with 

 the same flour, water, and salt, baked at the same heat and for the same time, and 

 having the same amount of crust and crumb. 



