226 EXCRETION. 



disassimilation ; or, at least, they diminish in a marked man- 

 ner the amount of matters excreted, particularly the urea. 

 Alcohol has a very decided influence of this kind. Its ac- 

 tion may be modified by the presence of salts and other 

 matters in the different alcoholic beverages, but in all direct 

 experiments, alcohol, taken either under normal conditions 

 of diet, when the diet is deficient, or when it is in excess, 

 diminishes the excretion of urea. The same is true of tea 

 and coffee. 1 



Influence of Muscular Exercise. There can be no doubt 

 that muscular exercise, under ordinary conditions of diet, in- 

 creases the proportion of many of the solid constituents of 

 the urine, particularly the urea. It is impossible to come to 

 any other conclusion after studying the elaborate researches 

 of Lehmann, a Hammond, 3 and others upon this subject. It 

 must be remembered, in considering the effects of exercise 

 upon the elimination of excrementitious matters, that the 

 modifications in the urine produced by food are very consid- 

 erable. "We have purposely considered the influence of food 

 before taking up other modifying conditions, so as to make 

 apparent an important element of error in some recent ob- 

 servations, which are at variance with the prevailing ideas 

 on this subject. When, for example, it has been shown that 

 restriction to a non-nitrogenous diet will immediately dimin- 

 ish the daily elimination of urea more than one-half, it is 

 evident that the diet must always be fully considered in ex- 

 periments upon the effects of exercise or other modifying 

 circumstances. 



There is another important point, also, which is not al- 

 ways taken into consideration in comparative observations 



1 This subject has already been considered under the head of Alimentation. 

 See vol. ii., Alimentation, p. 102, et seq. 



2 LEHMANN, Physiological Chemistry, Philadelphia, 1855 ; vol. i., p. 151. 



8 HAMMOND, The Relations which exist between Urea and Uric Acid. American 

 Journal of the Medical Sciences., Philadelphia, January, 1865, and Physiological 

 Memoirs, Philadelphia, 1863, p. 13. 



