564 VETERINARY PHYSIOLOGY 



Phenol— 



CeHg 



-0— H 





.0— S0„0K 



CgH^ 



is also linked with potassium sulphate, and excreted in the 

 urine. 



The amount of these ethereal sulphates depends upon the 

 activity of putrefaction in the intestine, and is a good index of 

 its extent. 



Dioxybenzene or Pyrocatechin — 



— 0-H 

 — 0— H 



is also linked to potassium sulphate and excreted. This com- 

 pound is always present in the urine of the horse. When 

 oxidised it yields a greenish-brown pigment when urine 

 containing it is allowed to stand. 



B. Neutral Sulphur. — A small quantity of sulphur is excreted 

 in a less oxidised state, in the form of neutral sulphur. The 

 most important compound of this kind is cystin, the disulphide 

 of amino-propionic acid — two molecules of amino-propionic acid 



linked by sulphur — 



Amino-propionic acid. 



I 

 Sulphur. 



i 

 Sulphur. 



I. 

 Amino-propionic acid. 



H H 



I I 



H— C— S — S— C— H 



I I 

 H— C— NH., HoNC— H 



C_OH HO— C 



II li 



o o 



