VARIATIONS IN THE URINE. 227 



upon the absolute quantities of urea eliminated during exer- 

 cise and repose, and that is the elimination of this principle 

 by the cutaneous surface. We have already seen that urea 

 is a constant constituent of the sweat. Speck, who found 

 that exercise usually increased the elimination of excremen- 

 titious matters, noted the fact that urea was not increased in 

 the urine when the sweat was very abundant. 1 



The very elaborate analysis of the principal observa- 

 tions on this subject by Parkes shows the discrepancies in 

 the experiments of different authors, and points out several 

 of the sources of error. 2 The weight of experimental evi- 

 dence at that time was decidedly in favor of an increase in 

 the elimination of urea by exercise ; and the observations 

 opposed to this view involved inaccuracies which would ex- 

 plain, in part at least, the contradictory results obtained. 

 Lately, new observations have been made, which are assumed 

 by some to show an actual diminution by exercise in the 

 quantity of urea excreted. Fick and Wislicenus, 3 Frank- 

 land, 4 and Haughton 5 have attempted to show that this is 



1 SPECK, Ueber die Wirkung der bis zur Ermudung gesteigerten korperlichen 

 Austrengung unter verschiedenen Verhaltnissen auf den Stoffwechsel. Archiv zur 

 Forderung der wissenschaftlichenHeilkunde, Gottingen, 1860, Bd. iv., S. 591. 



2 PARKES, The Composition of the Urine, London, 1860, p. 85, et scq. Dr. 

 Parkes has made some interesting observations, since the publication of 

 his work on the urine, upon the influence of muscular exercise, under a non- 

 nitrogenous diet, upon the elimination of urea. He found the amount of nitrogen 

 in the excreta slightly increased over the amount eliminated during a period 

 of rest, on the same diet The elimination by the skin and intestines was taken 

 into account in these experiments. PARKES, On tJie Elimination of Nitrogen by 

 the Kidneys and Intestines, during Rest and Exercise, on a Diet without Nitrogen. 

 Proceedings of the Royal Society, London, 1867, vol. xv., Xo. 89, p. 339, et seq. 



3 FICK AND WISLICENUS, On the Origin of Muscular Power. London, Edin- 

 burgh and Dublin Philosophical Magazine, London, Jan.-June, 1866, vol. xxxi., 

 p. 485, et seq. 



4 FRANKLAND, On the Origin of Muscular Power, Ibid, July-Dec., 1866, vol. 

 xxxii., p. 182, et seq. 



5 HAUGHTON*, Address on the Relation of Food to Work done by the Body, and 

 its Bearing upon Medical Practice. The Lancet, London, Aug. 15, Aug. 22, and 

 Aug. 29, 1868. 



