192 PHYSIOLOGICAL CHEMISTRY 



total amount of sulphur excreted per day is variable, but usually 

 is somewhat less than a gram. The chief source of urinary sul- 

 phate is the sulphur of the protein molecule. Most of this is 

 oxidized in the body, so that 75-80% of the total sulphur is pres- 

 ent as inorganic sulphate. The remainder is made up of organi- 

 cally bound sulphate, and of a mixture of traces of several com- 

 pounds containing sulphur in unoxidized form, such as sul- 

 phocyanate (which we already have met as a constituent of 

 saliva), cystin, sulphides, etc. 



Since the proteins are the chief source of urine sulphur, there 

 is a general parallelism between the nitrogen and sulphur excre- 

 tion, which often runs about as follows : N :H 2 S0 4 = 5 :1. But 

 this is by no means a constant ratio. 



The ethereal sulphates are compounds in which sulphuric acid 

 is conjugated with various phenols produced from the proteins 

 by putrefaction in the intestine. From tryptophane, indol and 

 skatol are produced and oxidized in the body to indoxyl and 

 skatoxyl which are then combined with sulphuric acid to make 

 ethereal sulphates. The synthesis of these compounds, as in the 

 case of the conjugated glucuromates, is a protective measure, 

 the toxic phenols being converted into relatively non-toxic 

 ethereal sulphates. 



Variations in the amount of protein in the diet cause rela- 

 tive as well as absolute variations in the different sulphur constit- 

 uents. If the amount of protein in the food is decreased, the in- 

 organic sulphates fall both in amount and in per cent of the total 

 sulphur which they represent. The amount of neutral sulphur 

 remains fairly constant, so that the per cent rises. Thus neutral 

 sulphur, like creatinine, probably is largely a product of endog- 

 enous tissue metabolism, since it is independent of the pro- 

 tein intake in the food. Neutral sulphur is increased in cystin- 

 uria, by chloroform and after taking cyanides, which are con- 

 verted into sulphocyanate. Putrefaction in the intestine de- 

 creases in amount on a low protein diet, so that ethereal sulphates 

 decrease, but usually not so rapidly as the total sulphur, so the 

 percentage increases somewhat. 



