EXCREMENTITIOUS SUBSTANCES. '87 



This, as will hereafter appear, is a point of considerable importance in the treat- 

 ment of diseases attended with excessive production of uric acid. Scarcely a 

 trace of uric acid has yet been detected in the muscles ; but it has been recently 

 found by Scherer in considerable quantity in the spleen, where it is accompanied 

 by another substance nearly related to it in composition, which he has also ob- 

 tained from the heart, both of man and of the ox. This substance, which has been 

 termed Ifypoxanthine, presents itself in the form of a white crystalline powder, 

 which is soluble in 180 parts of boiling water, but requires 1090 parts of cold 

 water for its solution, so that it is deposited on the cooling of a decoction of the 

 substance of the spleen. 1 Its formula is 50, 2H, 2N, 10; and it thus con- 

 tains 2 equivs. less of oxygen than hydrated Uric acid, into which it may very 

 probably be metamorphosed. 



58. Uric acid is almost uniformly replaced in the urine of herbivorous animals 

 by an acid of very different composition ; which, having been first distinguished 

 by Liebig in the urine of the horse, was named by him Hippuric acid. His 

 subsequent inquiries satisfied him that it also exists normally, though in com- 

 paratively small quantities, in the urine of Man, especially after the use of 

 vegetable food ; and if it is ever entirely absent, it is probably so only when the 

 diet is exclusively animal just as it is absent from the urine of calves while 

 suckling, being replaced in them by uric acid. Hippuric acid crystallizes from 

 hot solutions in the form of minute spangles, or of larger, obliquely-striated, 

 four-sided prisms, terminating at the two ends in two flat surfaces ; the element- 

 ary form, however, which is best seen in crystals obtained by slow evaporation, 

 is a vertical rhombic prism. This acid is devoid of smell, has a slightly bitter 

 but not an acid taste, dissolves in 400 parts of cold water, and very freely in 

 hot water, and reddens litmus-paper powerfully. Its formula is 18C, 8H, IN, 

 50, + HO ; and it is thus remarkable for the almost complete absence of nitro- 

 gen and for the large proportion of carbon, a constitution which approximates it 

 closely to the biliary compounds. When boiled with concentrated hydrochloric 

 acid, this substance undergoes a very remarkable change ; being resolved into 

 Grlycine or gelatin-sugar ( 33), and Benzoic acid, probably in the manner fol- 

 lowing, one additional equivalent of water being alone required. 



C. H. N. 0. C. H. N. 0. 



1 equiv. hydrated Hipp, acid = 189 1 6^1 f 4 5 1 4 = 1 equiv. Glycine. 

 1 equiv. Water . . = 1 111 14 5 3 = 1 equiv. Benzoic acid. 



1810 1 7J [18 10 1 7 



Various other reagents will cause the production of benzoic acid at the expense 

 of hippuric ; and this change takes place during the putrescent fermentation of 

 urine of which hippuric acid is a constituent. According to the view originally 

 suggested by Strecker, hippuric acid is really to be considered as a " conjugated 

 acid," formed by the union of benzoic acid, which he supposed to pre-exist in it, 

 with an adjunct composed of 4C, H3, IN, 20, which in separating takes to itself 

 an equiv. of water and forms glycine ; and this view (although since abandoned 

 by Strecker himself) is considered by Lehmann as the most probable, especially 

 since one of the biliary acids ( 68) appears to have an analogous constitution, 

 glycine being there also generated by the action of acids upon it. 2 The close 



1 "Ann. der Chem. und Pharm.," band Ixxiii. p. 328. 



2 See his "Physiological Chemistry," vol. i. pp. 189-192. The term " conjugated acid" 

 is applied to a class of compounds recently discovered, in which certain organic acids unite 

 with other and more basic bodies without losing anything of their acidity, still saturating 

 the same quantity of base as if the organic "adjunct" did not exist. This adjunct, which 

 follows the acid as an integral constituent through all its combinations, exerts an essential 

 influence on its physical, and even on many of its chemical properties. (Op. cit. p. 184.) 



