606 THE CHEMISTRY OF THE URINE 



excreted as conjugated sulphates (see p. 631), but the carboxyacids are 

 only in part so excreted. Inosit, which belongs to this group chemically, 

 has somewhat different physiological relationships to the other aro- 

 rnatics of urine. 



Phenol (CeHs.OH) and kresol (CH 3 .C 6 H 4 . OH). Traces of carbolic 

 acid are present in urine physiologically, but the " phenol " of the normal 

 fluid consists, as a matter of fact, mainly of the homologous kresol ; and, 

 of the isoineric forms of the latter, parakresol is the commonest. The 

 properties of this substance, however, closely resemble those of phenol 

 itself. The amount of phenol and kresol taken together may be upon a 

 mixed diet no more than some 30 mgrms. per diem. If the urine 

 be acidified and distilled, the distillate made alkaline, concentrated, and, 

 after concentration, neutralised, on the addition of bromine a whitish pre- 

 cipitate will appear, due mainly to the formation of the tribromphenols. 



Pyrocatechin (orthodihydroxybenzene) and hydrochinon (para- 

 dihydroxybenzene) C 6 H 4 (OH) 2 . Of these two isomeric substances 

 the former is a constant constituent of human urine in small 

 quantity; the latter is found probably only under exceptional cir- 

 cumstances. The former is easily removed from the acidified urine 

 by shaking with ether ; but its subsequent purification involves a 

 lengthy procedure. 1 It is a white crystalline volatile solid, easily 

 soluble in water. It gives a dark green coloration with ferric chloride, 

 which, on the addition of ammonia, becomes violet and afterwards 

 cherry-red. 



Inosit. This substance, from its sweet taste, was originally classed 

 with the sugars, and was known as " muscle sugar." It strictly belongs, 

 however, to the group of substances we are considering, as it is by com- 

 position hexahydroxybenzene (CH.OH) 6 . It appears in normal urine 

 with considerable frequency when polyuria is induced by diuretics or by 

 copious drinking. On the other hand, its appearance is not entirely 

 dependent upon the flushing of the tissues which such polyuria might 

 denote, as extreme polyuria is at other times not associated with 

 inosituria. It may occur in diabetes. Galloise found it in five out of 

 thirty cases. 



It may be separated from the urine by precipitation with acetate of 

 lead. The precipitate is decomposed with hydrogen sulphide, the fluid 

 concentrated, and finally precipitated by admixture with a large bulk of 

 alcohol. The alcohol precipitate is dissolved in water, the solution 

 mixed with an equal bulk of spirit and poured into ether, which pre- 

 cipitates the inosit almost pure. 



The substance forms crystals not unlike those of cholesterin. It is 

 optically inactive and does not ferment. It is said to yield sarcolactic 

 acid by the action of bacteria. 



Of the aromatic carboxyacids the following have been identified 

 in human urine: ParaJiydroxyplienyl-acetic acid OH.C 6 H 4 CH 2 .COOH; 

 parahydroxyplienyl-propionic acid OH.C 6 H 4 C 2 H 4 .COOH ; dihydroxy- 

 phenyl-acetic acid (OH) 2 CH 2 .COOH (the homogentisic acid of 

 Wolkow and Baumami) ; 2 and trihydroxyphenyl-propionic acid 

 (OH) 3 C 6 H 2 .C 2 H 4 .COOH (the uroleucic acid of Kirk). 



In the urine of herbivora other analogous compounds have been 



1 Of. Halliburton, "Chemical Physiology and Pathology," 1891, p. 745. 



2 Loc. cit., 1891, Bd. xv. S. 241. This is that isomeric acid which is related to hydro- 

 chinon. 



