EXAMINATION OF NORMAL AND ABNORMAL URINE. 381 



12. Examination of any organic or inorganic sediment, either 

 by chemical means or by the microscope. 



Samples of urine should always be drawn from the well- 

 mixed and exactly measured quantity of the total urine dis- 

 charged in 24 hours. 



Color. Normal urine is generally pale yellow or reddish-yel- 

 low, but it may be as colorless as water, or as dark brownish- 

 black as porter; a smoky tint generally indicates the presence 

 of blood, and a brownish-green suggests the presence of the 

 coloring matter of bile. 



The true nature of the normal coloring matters of urine is as 

 yet doubtful; the existence of at least two has, however, been 

 demonstrated; they have been named urobilin and urine-indican 

 or uroxanthin, and are, most likely, products of the decomposi- 

 tion of biliary matters. 



Abnormal coloring matters are chiefly those of blood, bile, 

 and of certain vegetables; thus, rhubarb and senna leaves cause 

 a reddish-yellow to deep red color, especially in alkaline urine; 

 santonin produces a bright yellow color, changing to red or 

 crimson on the addition of an alkali. Carbolic acid introduced 

 into the system causes a dark, or even black discoloration of 

 urine. 



The coloring matters of blood may be recognized by adding 

 to a few drops of urine a drop of tincture of guaiacum, and 

 agitating with a solution of ozonized ether (ethereal solution of 

 hydrogen dioxide) : the latter is colored blue in case hgemo- 

 globin is present. 



Detection of biliary coloring matter will be considered below. 



Odor. The normal odor of fresh urine is characteristic, and 

 is sometimes spoken of as aromatic; it is not known b} what 

 substance or substances this odor is caused. The ammoniacal 

 and putrescent odor which urine acquires on standing, is due to 

 the products of decomposition formed, chiefly to ammonia. 



A number of substances taken internally and separated by 

 the kidneys from the blood, cause the urine to assume a charac- 

 teristic odor; aromatic substances especially impart such odors; 

 oil of turpentine gives an odor reminding of violets, and the 

 odor of cubebs, copaiba, and other similar substances is promptly 



