506 OF SECKETION AND EXCRETION. 



last twelve, or rest hours of the forty-eight hours, an increase in the amount 

 of urea; and that, on the whole, the effect of the exertion of walking fifty- 

 six miles on a non-uitrogeuous diet was a total increase of only 1.589 

 gramme of nitrogen in one man, and in the other of only 0.223 gramme in 

 the forty-eight hours. In the fifth period the men once more returned to 

 their ordinary diet and occupation for four days, in which a considerable in- 

 crease of nitrogen over the average amount was observed; which however 

 is referred by Dr. Parkes, not to the elimination of the products of destroyed 

 muscle during the work period, but to an excess of nitrogenous food con- 

 sumed in the four days following the exercise. In the second series of ex- 

 periments two men were kept on the same nitrogeuized diet for sixteen days. 

 For four days they were kept at their ordinary employment; during two 

 days rested; returned to ordinary work for four days; took very active ex- 

 ercise for two days, walking twenty-four and thirty-five miles, and were then 

 for four days more on ordinary occupation. The changes that took place in 

 the urea were almost identical with those in the total nitrogen eliminated, and 

 so nearly equal to that in amount, that (allowance being made for what passed 

 by the bowels) it was certain none passed off, either during rest or exercise, 

 by the skin or lungs. The results were, that in the first period the amount 

 of urea was almost precisely the same in the two men. In the rest period it 

 increased nearly two grammes daily in each man, fell during the third period 

 to the former average, decreased greatly during the first thirty-six hours 

 of the exercise period as compared with the rest period, and increased in 

 the last twelve hours; in the last or after work period it also increased, 

 though in a less proportion than the total nitrogen. The first series of these 

 experiments undoubtedly corroborate the statement of Fick and \Yisliceuus, 

 that on a non-nitrogenous diet exercise produces no notable increase in the 

 nitrogen of the urine; although, when the subsequent period is also consid- 

 ered it does produce a slight increase. The second series showed that, with 

 an unchanged amount of nitrogen ingested, so far from there being any in- 

 crease, there was an actual diminution in the amount of urea eliminated 

 both during ordinary and during severe exercise, as compared with rest. 

 There was, on the other hand, an excess not great but long continued in 

 nitrogenous excretion after exercise; and there was a retention of the nitro- 

 gen in the system when it was again supplied 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 made up. In 

 some recent experiments by Weigeliu, 1 it appeared that if, after two hours 

 of strenuous muscular exercise, the amount of urea eliminated during the 

 succeeding two hours were determined, an increase of as much as 50 per 

 cent, on the ordinary average was sometimes observed. Persistent muscular 

 effort (tetanus) was found to produce more urea than the alternate contrac- 

 tion and elongation of muscle. In 1870 and 1871 a very important and com- 

 plete series of observations on the effects of protracted and severe muscular 

 exercise upon the excretion of nitrogen were made by Dr. Austin Flint, 

 aided by several other physiologists. 2 The subject of the experiment was 

 Mr. Weston, who, in the first instance walked 100 miles in twenty-one hours 

 and thirty-nine minutes, and subsequently attempted to walk 400 miles in 

 five consecutive days; which, however, he failed to accomplish. Dr. Flint 

 made a careful examination of the urine for five days preceding the walk, 

 .for the five days of the walk, and for five days after the walk. Mr. Weston 

 was thirty-one years of age, and his weight was about 120 Ibs. He smoked 



1 Roichert's Archiv, 1868, p. 207. 



2 See New York Medical Journal, June, 1871, pp. G09-697. 



