THE NEUTRAL SULPHUR OF THE URINE. 271 



true, both are then met with in large amount, but we may readily 

 suppose that the substances may have originated here directly, and 

 possibly as a result of some fermentative action. This, indeed, 

 appears the most likely explanation. 



Isolation. If leucin and tyrosin are present in the urine in small 

 amounts, they are held in solution. In the presence of larger 

 amounts the tyrosin may separate out, and can then be isolated from 

 the sediment and identified as described. Leucin, however, is rarely 

 found in this manner, and remains in solution even though very 

 large quantities are eliminated. 



To demonstrate both when they are held in solution, it is some- 

 times only necessary to concentrate a small amount of urine on a 

 water-bath and to examine the residual syrup with the microscope. 

 Otherwise it is advisable to precipitate the collected urine of 

 twenty-four hours, after removing any albumin that may be present, 

 with basic lead acetate. The filtrate is then freed from lead with 

 hydrogen sulphide, evaporated to a thick syrup, and set aside for 

 crystallization. Tyrosin and leucin can then be demonstrated by a 

 microscopical examination and identified in the usual manner (see 

 page 188). 



THE NEUTRAL SULPHUR BODIES OF THE URINE. 



In the section on the mineral constituents of the urine I pointed 

 out that the greater portion of the sulphur which is set free during 

 the metabolism of the nitrogenous constituents of the body is elimi- 

 nated in the urine in a completely oxidized form. A much smaller 

 fraction, however, escapes oxidation, and appears in the urine as 

 so-called neutral sulphur. Normally this constitutes about 12-15 

 per cent, of the total amount. Of the individual components which 

 go to make up this neutral sulphur comparatively little is known, 

 and it appears, moreover, that their character may be different in 

 different animals. In the urine of cats, and less constantly in that 

 of dogs, traces of thiosulphates are thus found, while in man this is 

 normally absent, and in disease even thiosulphuric acid has been found 

 in only one instance in typhoid fever. Ethyl sulphide, or a body 

 which gives rise to its formation when the urine is treated with 

 lime-water, is thus similarly not found in the urine of man, while it 

 is apparently a constant constituent of that of dogs. 



Of the normal constituents of the neutral sulphur which is found 

 in human urine, only two are actually known. These are the sulplw- 

 cyanides, which are found in small quantities in the saliva and the 

 gastric juice, and cystein, or a body which is closely related to it. 

 Whether or not taurocarbaminic acid is also constantly present has 

 not as yet been determined. I have shown, however, that to a 

 certain extent at least taurin is eliminated in this form when given 

 by the mouth. In cases of obstructive jaundice, moreover, or after 

 ligation of the common duct in dogs, the neutral sulphur may increase 



