PHYSICAL URINALYSIS. 173 



slightly aromatic. A putrid odor indicates tissue degeneration or 

 the decomposition of the urine within the body. 



3. Color. The color of normal urine ranges from that of water, 

 through the yellows, to reddish brown, the average being straw,, or 

 amber, color. The color is due to certain pigments. Concentrated 

 urine is more highly colored than that of low specific gravity. Ab- 

 normal urine exhibits greater fluctuations in color than that of 

 health. Red may indicate the presence of blood; a black color in- 

 dicates a certain form of cancer; green indicates jaundice, and 

 occurs sometimes in diabetes ; blue occurs in cholera and typhus. 



4. Transparency. Normal urine is transparent when voided, 

 becoming cloudy after standing, owing to the action of bacteria. 

 Pathological urine is often cloudy when first obtained, due to the 

 action of bacteria, the presence of blood, pus, etc., and the precipi- 

 tation of salts. Heat removes cloudiness due to precipitated urates, 

 but not when caused by bacteria., pus, or precipitated phosphates. 

 Acids will clear up any cloudiness due to precipitated phosphates, 

 but will increase turbidity arising from bacteria, albuminous casts, 

 and pus. 



5. Chemical reaction, This test consists in finding the action of 

 urine on litmus, an acid urine turning blue litmus red, and that 

 which is alkaline changing red to blue. Normal urine is acid, the 

 acidity being due to the acid sodium phosphate. Excessive acidity 

 is calculated to irritate the urinary passages and favors the forma- 

 tion of uric acid concretions. Alkalinity of the urine may be due 

 to the presence of ammonium carbonate (resulting from the de- 

 composition of urea by the agency of bacteria) or to an alkali of 

 sodium or potassium. In the former case the litmus paper turns 

 red again upon drying ; in the latter case it remains blue upon dry- 

 ing. 



6. Specific gravity. Normal urine (1,500 c.c.) has a specific 

 gravity ranging from 1.015 to 1.025, the average being 1.020, water 

 being taken as the standard. Low specific gravity may indicate 

 nephritis and organic albuminuria, though in functional albuminu- 

 ria the specific gravity is above normal. High specific gravity is 

 suggestive of melituria, and when it reaches 1.030 there is indicated 



