1867.] Dr. Parkes on the Elimination of Nitrogen. 



53 



quite unprepared for a result so close as that the difference in the ex- 

 cretion of nitrogen of the two men should be only 0*076 gramme, or 

 scarcely more than 1 grain daily. In the last four days S. passed a little 

 more nitrogen b}^ the urine than B., thereby reversing what had gone 

 before. The stools were not analyzed during this period, but I believe 

 that the nitrogen must have been furnished by the body during these 

 four days. As respects the effect of exercise on the intestinal nitrogen, 

 there was a slight increase in rest over the previous period and in ex- 

 ercise over the rest-period. 



If the following Table (p. 54) be analyzed, it will be found that the 

 loss of weight in the rest-period was attributable in S. almost entirely 

 to excess in the pulmonary and cutaneous excreta, while in B. it was 

 owing to increase in the urinary and intestinal excreta. It might be 

 presumed to have been chiefly water ; but the simultaneous changes in 

 the excretion of nitrogen give it interest. The channel of elimination, 

 in B. proves in another way that it was not owing to effect of external 

 temperature in the air. 



During the period of exertion the loss of weight was from increase in 

 the skin and lung excretion, and it is interesting to observe how parallel 

 it was in the two men ; the loss of weight was subsequently made up by 

 lessening of the skin and lung excreta. The intestinal excreta were not 

 influenced either way by the exercise ; and in spite of the great passage 

 of water by the skin, the urinary water was not affected. The antago- 

 nism commonly stated to exist between the excretion of water by the 

 skin and kidneys was not perceptible. 



Eocjplanation of tlie preceding fads. 

 Taking into account the experiments formerly recorded as well as 

 those in this paper, we have to explain the following phenomena. 



1. AVith an unchanged ingress of nitrogen there was a slight excess 

 of nitrogenous excretion during rest as compared with a period of ordi- 

 nary exercise. 



2. There was a decrease of urinary nitrogenous excretion during active 

 exercise as compared with a period of rest, and this was perceptible both 

 when the ingress of nitrogen was stopped, as well as Avhen nitrogen was 

 supplied in regular amount. 



3. There was an excess, not great, but long continued in nitrogenous 

 excretion after exercise. 



4. There was a retention of nitrogen in the system when it was again 

 supplied after having been cut off, after both rest and exercise, and 

 greatest in the latter case, showing that it is needed in the system, and 

 that an insufficient supply at one time must be subsequently compensated. 



In addition we cannot leave out of account the well-known dietetic 

 fact, based on experience, that much muscular work always demands 

 the supply of a larger amount of nitrogen. 



