202 A Manual of Veterinary Physiology. 



acid in starvation (when the animal becomes carnivorous) 

 or, as mentioned before, in the young animal still sucking 

 its mother. 



Hippuric Acid.— Our knowledge of the seat of formation 

 of this acid in the animal body is due to the experiments of 

 Bunge and Schmiedeberg, and I shall attempt here to 

 embody the authors' views on the subject.* 



The carbon of the food which is not rejected by means of 

 the lungs, unites with nitrogen and forms a series of bodies 

 which escape by the kidneys ; these bodies are urea, uric 

 acid, hippuric acid, creatin, and creatinin. Hippuric acid 

 is formed in the animal body by the combination of benzoic 

 acid and glycocoll, the latter arising possibly from the de- 

 composition of albuminous tissues, the former being derived 

 from the food through various aromatic combinations con- 

 tained in plants. 



Great doubts having arisen as to where the synthesis of 

 glycocoll and benzoic acid occurred, the authors, by means 

 of experimental inquiry, ascertained that the combination 

 occurred in the kidneys, that it was brought about by the 

 living cells of the kidney, and that the red blood corpuscles 

 took an active part in the process through the oxygen they 

 contain. 



They cautiously observe that in dogs only has the exclu- 

 sive formation in the kidney of hippuric acid been observed, 

 for rabbits can form this acid even when the kidneys arc 

 extirpated. 



Hippuric acid exists in the urine either as hippurate of 

 lime or potash, probably the former. There are no free 

 acids in the urine, even in carnivora : and in omnivora the 

 same holds good, the acidity of the fluid with them being- 

 due to acid salts. 



The amount of hippuric acid excreted varies with the 

 diet; it is increased by using meadow -hay and oat -straw, 

 and decreased by using clover, peas, wheat, oats, etc.; as 

 the urea rises the hippuric acid falls. 



According to Munk, a horse fed on meadow-hay excreted 

 * 'Physiological ami Pathological Chemistry, 1 Bunge. 



