6oo 



THE CHEMISTR Y OF THE URINE. 



progressive muscular atrophy, and in pseudo-hypertrophic paralysis. 

 According to Senator, no increase is produced by the paroxysms of 

 tetanus a fact which is of interest as bearing on the relation of 

 muscular activity to the urinary creatinin. 



(g) Hippuric acid. Hippuric acid is benzamido-acetic acid, or 

 benzoylglycin, C 6 H 5 .CO.NH.CH 2 .COOH ; in other words, it is a con- 

 densation product of benzoic and amido-acetic acids, in the formation 

 of which the hydroxyl group of the former is eliminated as water, 

 with an atom of hydrogen from the amido group of the latter. But 



FIG. 53. A. Creatinin ; B. Hippuric acid. 



the simplest artificial synthesis is obtained when monochlor-acetic acid 

 is heated with benzamide. 



C C H 5 CO.NH 2 +CH 2 C1.COOH = (C 6 H 6 .CO)NH.CH 2 .COOH+HC1 



In most mammals the synthesis by dehydrolysis occurs in the kidney ; 

 hippuric acid appearing in the urine, whenever benzoic acid, or pre- 

 cursors of benzoic acid, are taken by the mouth. The excretion of 

 hippuric acid is, indeed, mainly dependent upon the relative richness of 

 the diet in such precursors of benzoic acid. 



It is not necessary that benzoic acid should itself be ingested. A 

 benzene derivative containing a single "side-chain" is nearly always 

 oxidised in the body to benzoic acid. Such substances, therefore, as 



toluene, C 6 H 5 .CH 3 ; cinnamic acid, CJL.CH.OH.COOH 



or 



phenyl- 



propionic acid, C C H 5 .CH 2 .CH 2 .COOH, all give rise to an excretion of 

 hippuric acid when they are taken by the mouth. Aromatic compounds 

 of this type are abundantly present in some forms of vegetable food, as 



