390 INFLUENCE OF MUSCULAR EXERCISE ON THE URINE. [BOOK I. 



It will be observed that, in both cases, the nitrogen actually excreted 

 during and immediately after exercise appears to diminish from the 

 standard of A. This fact will be afterwards discussed. It is not so 

 much the relative as the absolute elimination of nitrogen which we are now 

 considering. 



Conciu- Having determined the excretion of nitrogen for 



sions. some hours before, during, and after a period of muscular 



exertion, Fick and Wislicenus had a key to the amount of albuminous 

 matter which had in the same interval of time been decomposed with- 

 in the body ; but one which required certain assumptions for its use. 



In the first place it was assumed that all the nitrogen escapes by 

 the urine. This is not strictly true, since some is removed in the 

 faeces and some in the sweat; both these sources of loss were 

 neglected. 



In the second place it was assumed that the nitrogen excreted 

 during labour (B), together with that excreted during the six hours 

 succeeding labour (C), fully represented all the albuminous matter 

 decomposed during the period of labour. This is the most vulnerable 

 point of the argument, and deserves some consideration. 



It is clearly improbable that the nitrogen eliminated in the urine 

 (B) emitted during the occurrence of labour exactly represents the 

 albuminous decomposition during the same period. The act of 

 decomposition may not and probably does not occur at one step. 

 Intermediate stages between proteid and the ultimate form in which 

 the nitrogen escapes, are first formed and may possibly remain at 

 the seat of manufacture, or in some other organ, until long after 

 the period of exercise. Such intermediate stages would there- 

 fore have no representative in the urine excreted during labour. 

 But this lagging of elimination behind the time of formation, as the 

 observers themselves pointed out, is true also of the nitrogenous pro- 

 ducts of the period before labour. If the excretions of the period B 

 lack some of the decomposition-products proper to that period, it is 

 also true that they possess some which are proper to A. In order 

 amply to cover the effects of this retardation of excretion, Fick and 

 Wislicenus added to the nitrogen excreted during the eight hours 

 of the ascent the whole of that which was excreted during the six 

 hours following. 



In the third place an assumption was necessary in order to con- 

 vert the nitrogen excreted into terms of albuminous substance. The 

 albuminous substances differ in constitution among themselves ; and 

 it is impossible to say which kind is chiefly taxed to supply the 

 nitrogen excreted during exercise. But all albuminous bodies except 

 permanent cartilage, contain more than 15p.c. of nitrogen. If, 

 therefore, we assume that every 15 parts of nitrogen excreted repre- 

 sent 100 parts of albuminous substance decomposed, we shall obtain 

 a quantity of albuminous matter greater than could possibly have 

 been destroyed in the body within the given time 



