EXAMINATION OF THE URINE. 113 



2. Fifty cubic centimeters of urine are gently shaken with 

 the same quantity of perfectly pure ether, which must 

 contain no alcohol or acid; the ethereal extract is then 

 evaporated and the residue dissolved in 2 to 3 cc. of 

 absolute alcohol. The solution shows the green fluorescence 

 and the absorption-band. Its color, curiously enough, is 

 often pure yellow. 



XII. DETECTION OF UNOXIDIZED SULPHUR. 



Pour some hydrochloric acid on a small piece of zinc in a 

 dish, let the acid act for a short time, then pour off the hydro- 

 chloric acid and rinse the zinc with water. Put the zinc in 

 a flask with about 50 cc. of urine, add enough hydrochloric 

 acid to cause an evolution of hydrogen, and fasten a strip of 

 filter-paper, which has been previously moistened with lead 

 acetate solution, in the neck of the flask by means of a loosely 

 fitting cork. The paper turns brown or black after some 

 time from the formation of lead sulphide. Only the neutral 

 sulphur of the urine forms hydrogen sulphide with nascent 

 hydrogen. Neither the sulphuric acid nor the ethereal sul- 

 phates are acted on. 



XIII. DETECTION OF PEPSIN. 



Divide the urine to be examined, about 50 cc., into two 

 equal parts, heat one-half to boiling, and let cool; the second 

 half is not heated To each of the two portions add 4 or 5 

 drops of hydrochloric acid. Ten cubic centimeters of the 

 urine thus prepared are placed in a test-tube with a shred of 

 fibrin and digested at 40. It is advisable to make two tests 

 with each portion of the urine. The shred of fibrin dissolves 

 in the unboiled portion of the urine in a longer or shorter 

 time according to the amount of pepsin present, but not in 

 the boiled portion. The unboiled portion of the urine in 



