428 EXCRETION. 



extent in the chlorides. The results of experiments upon this point seem to show that 

 water taken in excess increases the activity of disassimilation. 



The ordinary meals invariably increase the solid constituents of the urine, the most 

 constant and uniform increase being in the proportion of urea. This, however, depends 

 to a great extent upon the kind of food taken. The increase is usually noted during the 

 first hour after a meal, and it attains its maximum at the third or fourth hour. The inor- 

 ganic matters are increased as well as the excrementitious principles proper. The urine 

 passed after food has been called urina cibi, under the idea that it is to be distinguished 

 from the urine supposed to be derived exclusively from disassimilation of the body, which 

 is called the urina sanguinis. 



It is an interesting and important question to determine the influence of different 

 kinds of food upon the composition of the urine, particularly the comparative effects of a 

 nitrogenized and a non-nitrogenized diet. Lehmann has made some very striking obser- 

 vations upon this point, and his results have been fully confirmed by many other physi- 

 ologists of authority. Without discussing elaborately all of these observations, it is 

 sufficient to state that the ingestion of an excess of nitrogenized principles always pro- 

 duced a great increase in the proportion of the nitrogenized constituents of the urine, 

 particularly the urea. On a non-nitrogenized diet, the proportion of urea was found to 

 be diminished more than one-half. The results of the experiments of Lehmann are so 

 striking that we quote them in full : 



"My experiments show that the amount of urea which is excreted is extremely 

 dependent on the nature of the food which has been previously taken. On a purely ani- 

 mal diet, or on food very rich in nitrogen, there were often two-fifths more urea excreted 

 than on a mixed diet ; while, on a mixed diet, there was almost one-third more than on 

 a purely vegetable diet ; while, finally, on a non-nitrogenous diet, the amount of urea 

 was less than half the quantity excreted during an ordinary mixed diet. 



" In my experiments on the influenc3 of various kinds of food on the animal organism, 

 and especially on the urine, I arrived at the above results, which in mean numbers may 

 be expressed as follows : On a well-regulated mixed diet I discharged, in twenty-four 

 hours, 32-5 grammes of urea (I give the mean of fifteen observations) ; on a purely ani- 

 mal diet, 53-2 grammes (the mean of twelve observations) ; on a vegetable diet, 22-5 

 grammes (the mean of twelve observations) ; and on a non-nitrogenous diet, 15-4 grammes 

 (the mean of three observations)." 



With regard to the influence of food upon the inorganic constituents ot the urine, it 

 may be stated in general terms that the ingestion of mineral substances increases their 

 proportion in the excretions. We have already alluded to this fact in treating of the 

 different inorganic salts. 



There are certain articles which, when taken into the system, the diet being regular, 

 seem to retard the process of disassimilation ; or, at least, they diminish, in a marked 

 manner, the amount of matters excreted, particularly urea. Alcohol has a very decided 

 influence of this kind. Its action may be modified by the presence of salts and other 

 matters in the different alcoholic beverages, but, in nearly all direct experiments, alco- 

 hol, either taken under normal conditions of diet, when the diet is deficient, or when it 

 is in excess, diminishes the excretion of urea. The same may be stated in general terms 

 of tea and coffee. 



Influence of Muscular Exercise. There can be no doubt that muscular exercise, under 

 ordinary conditions of diet, increases the proportion of many of the solid constituents of 

 the urine, particularly the urea ; but 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 considerable. We have purposely considered the influ- 

 ence of food before taking up other modifying conditions, so as to make apparent an 

 important element of error in some recent observations which are at variance with the 



