182 THE MICRO SCO PI ST. 



pressure under a strip of thin glass. If there is no coagula, 

 the liquid may rest for a short time, and a drop from the bot- 

 tom examined. The urine may also be tested for albumen after 

 separating the solid matter by filtering. When the coloring 

 matter of the blood is present, it will coagulate with the albu- 

 men, giving it a red or brown color. When the fibrin, in its 

 soluble form, is present, it usually coagulates spontaneously on 

 cooling, causing the urine to become gelatinous. The coagulum 

 of fibrin, when pressed between glasses, is generally composed 

 of minute amorphous particles, with a few red blood corpuscles, 

 quite different from the granular mucus corpuscles, for which it 

 might be mistaken without microscopic examination. 



Bile or purpurine in urine has nearly the same color as when 

 blood is present; hence, unless the blood corpuscles are present, 

 we should apply the tests for the detection of those substances 

 before finally deciding. Purpurine will be dissolved by treat- 

 ing with warm alcohol, or may be precipitated by adding a 

 little warm aqueous solution of urate of ammonia, which on cool- 

 ing will fall down, carrying with it the coloring matter. Bile 

 may be tested by pouring a few drops of urine on a white 

 plate, and adding carefully a drop or two of nitric acid. When 

 bile is present in any considerable quantity, the liquid becomes 

 successively pale-green, violet, pink, and yellow, the color 

 rapidly changing as the acid mixes with the urine. When 

 only slight traces of bile are. present, the urine should be con- 

 centrated by evaporation. 



When semen is present in urine, it may easily be detected 

 under the microscope, by the appearance of minute animalcu- 

 les, always found in the spermatic fluid, and hence called sper- 

 matozoa. They are oval in shape, with long and delicate tails. 

 Traces of albumen may generally be detected in urine contain- 

 ing semen. 



