PHYSIOLOGICAL CHEMISTRY. 

 THE SULPHUR EXCRETION. 



The sulphur in the urine is found in several compounds and 

 comes from different sources. A small part has its origin in 

 traces of sulphates taken directly in food and natural waters; 

 some comes from the sulphur existing- in peculiar combina- 

 tions in certain vegetables, while the largest part has its origin 

 in the sulphur of proteins, which undergoes more or less com- 

 plete oxidation before elimination through the kidneys. Most 

 of this sulphuric acid of oxidation combines with alkalies for 

 elimination; if fixed alkalies are deficient ammonium sulphate 

 is formed and this ammonia therefore escapes the natural oxi- 

 dation to urea. 



It has been explained in an earlier chapter that in the pu- 

 trefactive changes taking place in the intestines certain phenol 

 bodies are split off from proteins there remaining, or perhaps 

 in most cases from the unabsorbed protein derivatives. A 

 very considerable part of these phenol bodies escapes with the 

 feces, but another portion, often much increased in disease, is 

 absorbed by the blood vessels from the lower intestine and car- 

 ried to the liver where combination with sulphuric acid is 

 effected, probably through some kind of enzymic action. 

 The ethereal sulphate so formed is discharged finally with the 

 urine. The fraction of the sulphuric acid so voided is ex- 

 tremely variable, reaching sometimes 20 per cent of the whole. 

 The most abundant of these combinations are salts of phenyl-, 

 cresyl-, indoxyl-, and skatoxyl-sulphuric acid, the structural 

 relations of which are shown by the following formulas : 



CH 



HC C C.O.S0 2 OH 



H 5 01 SO CH 3 .C 6 H 4 CM I II II 



H0/ S0 * ' HO/ 80 * ' HC C CH 



C N 

 H H 



Phenyl-sulphuric acid Cresyl-sulphuric acid Indoxyl-sulphuric acid 



Skatoxyl-sulphuric acid is the methyl derivative of indoxyl- 

 sulphuric acid. Phenyl- and cresyl-sulphuric acids are fre- 



