URINE. 171 



tity of fluid that has been taken into the system, that it is im- 

 possible (without taking other facts into consideration) to de- 

 termine from the urine alone, whether a mere increase or de- 

 crease of the solid constituents is due to diseased action. Pale 

 urine, more or less like water, may be fairly considered deficient 

 in solid matters, while a deep brown colour is indicative of an 

 abundance of these constituents. 



The specific gravity, 1 and still more the determination of the 

 solid constituents in the manner which has been already de- 

 scribed, will give the required information. The colour of the 

 urine is sometimes deceptive, especially the fiery red that occurs 

 during fevers. Urine of this sort is frequently found to be 

 poorer in solid constituents, and its specific gravity lower than 

 we should have anticipated from its colour : it is usually, how- 

 ever, more abundant in uric acid than normal urine. 



2. Increase or decrease of free lactic acid. 



With a little practice we may form a rough estimate of the 

 increase of free acid, by observing the colour which the urine 

 imparts to blue litmus paper. If neither the blue nor the red 

 litmus paper is affected the urine is neutral. 



3. Increase, decrease, or absence of urea. 



In the course of my analyses, I have found that the quantity 

 of urea may vary from 0*3g to 2'4 in fresh urine ; I have ob- 

 served, however, at the same time, that these statements are 

 very deceptive, if the amount of solid residue is not at the same 

 time given. It is only by comparing it with the solid residue 

 that we can judge whether the urea has increased or decreased 

 in an extraordinary manner. In healthy urine the urea may 

 probably fluctuate from i to J of the weight of the solid con- 

 stituents. Further experience is wanted to show whether an in- 

 crease or decrease of this constituent (apart from other changes) 

 implies a diseased state of the urine. 



Urine has been known to yield crystals of nitrate of urea, 



1 The common urinometer is sufficiently accurate for ordinary cases. 



