4i8 



VETERINARY PHYSIOLOGY 



on a flesh-free diet is very constant in each individual, and 

 does not vary with the amount of protein food taken. 

 4. Hippurie Acid. This is benz-amino-acetic acid 



O 



-C 



H 



H O 



_N C C H 



H 



It is formed from benzoic acid taken in the food by linking 

 it to glycocoll ammo-acetic acid. This synthesis appears to 

 take place in the kidneys, for it has been found that hippuric 

 acid is not formed when these organs are excised, and that, 

 when blood containing benzoates is circulated through them, 

 hippuric acid is produced. Its chief interest is in the fact 

 that it is one of the first organic compounds which were 

 demonstrated to be formed synthetically in the animal 

 body. Normally it is absent from the urine of carnivora, 

 but in the urine of herbivora its amount is considerable. 

 It is formed from the benzoic acid in the food, and it is 

 therefore abundant upon a diet of grass or hay and smaller 

 in amount when oats or beans are given. 



II. Sulphur-containing Bodies 



The sulphur excreted in the urine is derived from the sulphur 

 of the protein molecule, and the amount of sulphur excreted 

 may be taken as a measure of the amount of protein decomposed. 

 This is sometimes used as a check upon an estimation from 

 the excretion of nitrogen. 



A. Acid Sulphur. The greater part of the sulphur is fully 

 oxidised to S0 3 . (a) Preformed Sulphates. The greater quantity 

 of this is linked with bases to form ordinary sulphates. 



(6) A small quantity is in organic combination, linked to 

 benzene compounds, Ethereal Sulphates. The indol, skatol, 

 and phenol (see p. 372), formed by the putrefaction of 

 proteins in the bowel or from the benzene compounds in the 

 food of herbivora, being excreted in the urine in an oxidised 

 form linked with sulphuric acid. Indol, as already shown, 

 is related to amido-ethyl-benzene. 



