44 



The precipitated phosphates are colored reddish brown 

 and fall in a thick cloud to the bottom of the tube. 



Almen's Test. Add a few drops of freshly made 

 5% alcoholic tincture of guaiacum to the suspected urine. 

 Shake well and add a few drops of hydrogen dioxide or of 

 old oil of turpentine, and the mixture will turn greenish 

 blue. The hemoglobin will change the color of the pre- 

 cipitate to blue. The test will not respond to a small quan- 

 tity of blood. 



Hemin Test. If some blood or sediment supposed to 

 contain blood be heated carefully with some glacial acetic 

 acid and a trace of sodium chloride, and then slowly evap- 

 orated in the air, brownish yellow rhombic crystals of 

 hemin are found. 



The spectroscope and microscope are also used in 

 blood tests. 



Melanine. In certain cases of melanosis this pigment 

 appears in the urine, which, when emitted is clear, but gradually 

 becomes of a deep brown, or even black color. 



Ordinarily melanine exists in solution in the urine, but 

 sometimes in the form of brownish or black sediment, recog- 

 nizable by microscopic examination. Melanine may possess a 

 diagnostic significance when the melanosis is beyond the reach 

 of examination by eye or touch. 



It may disappear from the urine when the disease is arrested, 

 or it may remain stationary. Oxidizing agents, such as chromic 

 acid and fuming nitric acid, transform the principle melanine, 

 causing gradually with the first and immediately with the second 

 a black coloration. According to Zeller, the most delicate test for 

 melanine is bromine water. With melanine it gives at first a yel- 

 low precipitate, which gradually blackens. Urobilin gives a yel- 

 low precipitate with the same reagent, but it does not blacken. 



The practical significance of this condition (melanuria) is 

 greatly limited by the fact that the urine may contain a large 

 quantity of melanine in wasting diseases, whilst that derived 

 from individuals suffering from melanotic cancer or sarcoma may 

 be entirely free from it. Senator has recently confirmed this view 

 by a series of clinical observations. Nevertheless, as an adjunct 

 in diagnosis, the tests given are of undoubted utility. 



