420 VETEKINAKY PHYSIOLOGY 



In earnivora their amount of these depends upon the activity 

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

 extent. In herbivora they are formed from the aromatic 

 compounds in the food. 



When Dioxybenzene or Pyroeatechin is formed in the body, 

 it too is linked to sulphate of potassium and excreted. It is 

 always present in the urine of the horse, and when urine 

 containing this substance stands, it becomes oxidised and 

 yields a greenish brown or black pigment. 



H 

 H 



B. Neutral Sulphur. A small quantity of sulphur is ex- 

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

 In man 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. 



1 

 Sulphur. 



Sulphur. 



I 

 Amino-propionic acid. 



In some individuals and in certain conditions of the 

 metabolism not yet fully understood, the amount of cystin 

 is increased, and it then tends to crystallise out in peculiar 

 hexagonal plates. 



III. Phosphorus-containing Bodies 



In herbivorous animals phosphates are practically absent 

 from the urine. They are excreted from the mucous membrane 

 of the bowel. Hence, in the horse, crystals of triple phosphates 

 are found in the faeces, not in the urine. 



In carnivores the phosphorus in the urine is derived partly 



