VARIATIONS IN THE TJEINE. 229 



acid is increased, and sometimes diminished. The sulphates, 

 phosphates, and chlorides are generally increased. 



The general result of experimental observations on the 

 effects of exercise upon the urine may be summed up in the 

 proposition that this condition increases the activity of the 

 nutritive processes, and produces a corresponding activity in 

 the function of disassimilation, as indicated by the amount 

 of excrementitious matters separated by the kidneys. 1 



Influence of Mental Exertion. Although the influence 

 of mental exertion upon the composition of the urine has 

 not been very much studied, the results of the investigations 

 which have been made upon this subject are, in many re- 

 gards, quite satisfactory. It is a matter of common remark 

 that the secretion of urine is very often modified to a very 

 great extent through the nervous system. Fear, anger, and 

 various violent emotions sometimes produce a sudden and co- 

 pious secretion of urine containing a large amount of water, 

 and this phenomenon is very often observed in cases of hys- 

 teria. Yery intense mental exertion will occasionally pro- 

 duce the same result. We have often observed a frequent 

 desire to urinate during a few hours of intense and unre- 

 mitting mental labor; and on one occasion, being struck 

 with the amount of urine voided, it was found, on exami- 

 nation, to present scarcely any acidity and a specific gravity 

 of about 1002. The interesting point in this connection, 

 however, is to observe the influence of mental labor upon 



1 Dr. J. C. Draper made, in 1856, a number of observations upon the effect 

 of exercise on the excretion of urea, from which he concluded that rest does 

 not diminish this excretion, and that exercise does not increase, but actually 

 lessens, the quantity discharged. These conclusions are arrived at by compar- 

 ing the amount of urea excreted by a patient confined to the bed with a frac- 

 tured leg, with the average of eighteen observations upon other persons. The 

 necessary experimental conditions are no better fulfilled in the other observa- 

 tions than in this, and the conclusions arrived at cannot therefore be accepted, 

 in opposition to the accurate experiments of other observers (DRAPER, 7s Mus- 

 cular Motion the Cause of tJie Production of Urea ? New York Journal of Medi- 

 cine, 1856, New Series, vol. xvi., p. 155, et seg.). 



