788 THE UEINE. 



Chemical Tests. For practical purposes the chemical examina- 

 tion of the urine is very simple. Quantitative analysis is of com- 

 paratively small value, as all ingredients of the urine, at least 

 after it has stood for a day or two, become visible with the 

 microscope, and the amount of urea, which, as such, cannot be 

 seen under the microscope, is in a constant proportion to the uric 

 acid and its salts. It forms at least the half of all the organic 

 constituents. 



The urine, as brought for examination, is either transparent 

 or cloudy. After the sediment has been deposited, we pour a small 

 portion from the upper parts of the liquid into a test-tube, im- 

 material what reaction the urine may give, and boil it over a 

 spirit-lamp. ' The results are as follows : 



(a) The urine is transparent, and by being boiled remains 

 unchanged ; if a small sediment is present in the original fluid, 

 this feature indicates normal urine. 



(~b) The urine is transparent, but after boiling becomes 

 cloudy. By adding a few drops of acetic acid, the urine clears up, 

 and this shows an increased amount of phosphates ; if efferves- 

 cence occurs upon the addition of the acid, carbonate of lime or 

 carbonate of ammonia is present. If the cloudiness remains after 

 the addition of the acid, we know that albumen is present, and, if 

 in large quantities, the urine is converted into a consistent, jelly- 

 like mass, easily spattering during the process of boiling. From 

 the sediment of the acidulated urine collected at the bottom of 

 the test-tube, an approximative estimation of the amount of albu- 

 men may be made. 



(c) The urine is cloudy, and by being boiled clears up entirely. 

 This means an excess of the urates, especially of the urate of 

 soda. 



(d) The urine is cloudy and remains so after boiling, or 

 increases in cloudiness. The same process must be resorted to 

 as in case (cj, with the same diagnosis. 



(e) The urine is cloudy and remains unchanged by boiling 

 and by addition of acetic acid. This proves the presence of a large 

 amount of the organisms of decomposition, micrococci, bacteria, 

 and leptothrix in alkaline urine, and oidium or fully developed 

 mildew in acid urine. 



An important chemical test is that for grape-sugar. Suspicion 

 arises of its presence, when for some time a large quantity of a 

 straw-yellow colored urine of a high specific gravity is passed. 

 Small quantities of grape-sugar may be present temporarily and 



