224: EXCRETION. 



"Water and liquids generally always increase the propor- 

 tion of water in the urine and diminish the specific gravity. 

 This is so marked after the ingestion of large quantities 

 of liquids, that the urine passed under these conditions is 

 sometimes spoken of by physiologists as the urina potus. 

 This must be borne in mind in clinical examinations of the 

 urine. It is a curious fact, however, that when an excess of 

 water has been taken for purposes of experiment, the diet 

 being carefully regulated, the absolute amount of solid mat- 

 ters excreted is considerably increased. This is particularly 

 marked in the urea, but it is noticeable in the sulphates and 

 phosphates, 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 disassimi- 

 lation. 1 



The ordinary meals invariably increase the solid constit- 

 uents 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 at- 

 tains 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 disas- 

 similation of the body, 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 nitrogen- 

 ized and a non-nitrogenized diet. Lehmann has made some 

 very striking observations upon this point, and his results have 

 been fully confirmed by many other physiologists of author- 

 ity. Without discussing elaborately all of these observations, 

 it is sufficient to state that the ingestion of an excess of ni- 

 trogenized principles always produced a great increase in 



1 PARKES, op. cit., p. 67, et seq. 



