230 EXCKETION. 



the elimination of solid matters, as contrasted with the 

 amount of excretion during complete repose, the condi- 

 tions of alimentation in the two instances being identical. 



The most extended series of observations upon this sub- 

 ject, in which all the necessary experimental conditions were 

 fulfilled, are those of Prof. Hammond. These experiments 

 commenced with a standard series of observations, under fixed 

 conditions of diet, exercise, etc., extending over a period of 

 ten days. With a view, then, of determining the influence 

 of increased mental exertion, the number of hours in the day 

 appropriated to study was doubled, the conditions of food 

 and exercise remaining the same as in the standard series. 

 The average of a series of observations, extending over ten 

 days, showed an increase in the quantity of the urine, and 

 an increase, also, in the quantity of all of its solid constituents, 

 with the exception of uric acid, the proportion of which was 

 notably diminished. The amount of variation was as follows : 



Average of ten days in the standard series : Quantity of 

 urine, 37*95 oz. ; urea, 671*32 grains; uric acid, 14*44 

 grains ; chlorine, 154'29 grains ; phosphoric acid, 43*66 

 grains ; and sulphuric acid, 38*47 grains. 



Average of ten days with increased mental exertion : 

 Quantity of urine, 43*56 oz. ; urea, 749*33 grains ; uric acid, 

 10*75 grains ; chlorine, 172*62 grains ; phosphoric acid, 66*15 

 grains ; sulphuric acid, 49*05 grains. 



In another series of experiments, also extending over ten 

 days, in which there was absence, as far as practicable, of 

 mental exertion, the quantity of urine was diminished, and 

 there was a decrease in the proportion of all of its solid con- 

 stituents. 1 



These interesting observations have since been confirmed 

 by a number of different series of experiments ; 3 and in a 



1 HAMMOND, Urological Contributions. American Journal of the Medical Sci- 

 ences, Philadelphia, 1856, New Series, vol. xxxi., p. 330, etseq., and Physiological 

 Memoirs, Philadelphia, 1863, p. 17, etseq. 



2 THUDICHUM, A Treatise on the Pathology of the Urine, London, 1858, pp. 

 163, 164. 



