DISEASES OF THE URINARY SYSTEM. 261 



creased, owing to the excess of water eliminated through 

 the kidneys. 



The amount of urine may be much increased without any 

 augmentation in the amount of solid constituents. 



The specific gravity of the urine, however, is, as a rule, in 

 inverse proportion to the amount passed ; but under some 

 conditions, as in diabetes mellitus, the density is high, 

 although the urine is abundant. Again, we cannot con- 

 clude that there is an excess of solids present when the 

 specific gravity is high, for this may be due to deficiency 

 of water. 



The re-action of the urine is normally alkaline, though in 

 certain diseases it sometimes becomes acid. The reaction 

 may be tested by litmus paper. If alkaline, urine turns red 

 litmus blue ; if acid, it turns blue litmus red. 



We have already said that the amount of urea excreted 

 may be increased or diminished under various abnormal 

 conditions. 



ABNORMAL CONSTITUENTS PRESENT IN THE 

 URINE IN DISEASE.— Blood.— Blood is sometimes present 

 in the urinary secretion, and may be derived from the 

 kidneys, ureter, bladder, or from the urethra. 



The passing of blood in the urine is termed hsematuria. 



When the blood has its source in the kidneys, it gives a 

 general red or brownish smoky hue to the urine ; which, on 

 standing, deposits a brownish red sediment, in which blood- 

 casts are often present. 



In hemorrhage from the bladder, the blood is far less 

 intimately mixed with the urine, and often appears only 

 toward the end of micturition, while the urine is of a 

 pinkish or blood-red colour, and is associated with the 

 symptoms of vesical disease. 



Where blood is derived from the urethra, it is voided 

 independently of micturition. 



