ELIMINATION OF NITROGEN 341 



urina potus ; but when an excess of water has been taken for purposes 

 of experiment, the diet being carefully regulated, the absolute quantity 

 of solid matters excreted is considerably increased. This is particularly 

 marked as regards urea, but it is noticeable in the sulphates and phos- 

 phates, though not to any great extent in the chlorides. The results of 

 experiments on this point seem to show that water taken in excess 

 increases the activity of katabolism. 



The ordinary meals 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 on the kind of food taken. 

 The increase usually is noted during the first hour after a meal and 

 attains its maximum at the third or fourth hour. The inorganic matters 

 are increased as well as the excrementitious substances proper. The 

 urine passed after taking food has been called urina cibi, under the idea 

 that it is to be distinguished from the urine supposed to be derived 

 exclusively from katabolism, which is called the urina sanguinis. 



It is an important question, to determine the influence of different 

 kinds of food on the composition of the urine, particularly the compara- 

 tive effects of a nitrogenous and a non-nitrogenous diet. Lehmann 

 made a number of observations on this point, and his results have been 

 confirmed by many other physiologists. Without discussing fully all 

 these observations, it is sufficient to state that the ingestion of an excess 

 of nitrogenous food always produced a great increase in the proportion 

 of the nitrogenous constituents of the urine, particularly urea. On a 

 non-nitrogenous diet, the proportion of urea was found to be diminished 

 more than one-half. The general results of the experiments of Lehmann 

 are embodied in the following quotation: 



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

 is extremely dependent on the nature of the food which has been pre- 

 viously taken. On a purely animal 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." 



The influence of food is not confined to the period when any particu- 

 lar kind of food is taken, but is continued for many hours after a return 

 to the ordinary diet. 



In regard to the influence of food on the inorganic constituents of 

 the urine, it may be stated in general terms that the ingestion of 

 mineral substances increases their proportion in the excretions. 



There are certain articles which, when taken into the system, the 



