90 CHEMICAL COMPONENTS OF THE HUMAN BODY. 



tine by any known chemical process ; and there is no evidence that such con- 

 version ever takes place in the living body. Looking, then, to the nature of 

 creatine itself, to its relations to creatinine and to urea, and to the fact that it is 

 a constituent of urine, there can be no doubt whatever that, so far from being 

 an alimentary substance, whose presence in the muscular tissue serves an 

 important purpose in nutrition, 1 it is from the first destined to excretion, and is 

 received back into the circulation by absorption from the muscular tissue, to 

 be eliminated chiefly under different forms, through the kidneys. As it is 

 found so constantly in the juice of flesh, more abundantly in that of wild and 

 hunted animals than in that of tame and domesticated races, and most abund- 

 antly of all in the substance of that never-resting muscle, the heart, it may be 

 fairly presumed to be a product of the disintegration of the muscular tissue; and, 

 so far as we at present know, it is the first product of that metamorphosis. Of 

 the mode in which that change is effected, however, or of the nature of the com- 

 plementary substances into which the protein-compound resolves itself, we are 

 at present entirely ignorant. 



62. Some light upon this last point, however, may possibly be derived from 

 the study of the other constituents of the "juice of flesh." In this Liebig 

 occasionally detected an acid, to which he has given the name of Inosic ; this 

 is not crystallizable, but forms a syrupy fluid readily dissolving in water, and 

 possesses an agreeable taste of the juice of meat. It reddens litmus strongly, 

 and forms crystallizable salt with bases. Its formula is considered to be IOC, 

 6H, 2N, 100+ HO; and it is thus remarkable for the large proportion of 

 oxygen which- it contains. It has not been detected either in the urine or in 

 any other excretion; and if its absence in the excretory fluids should be sub- 

 stantiated, it must evidently undergo some metamorphosis in its passage from 

 the muscles to the final outlets of the products of their disintegration. Dr. Gr. 

 Bird has pointed out (op. cit. p. 37) that the constituents of Inosinic acid are 

 exactly those of Acetic acid, Oxalic acid, and Urea ; 



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



43 3=1 equiv. Acetic acid. 



4 6=2 equivs. Oxalic acid. 



1 equiv. hydrated Inosinic acid= 10 7 2 11 =-1 2 4 2 2=1 equiv. Urea. 



10 7 2 11 



and suggests this as a possible resolution of the first-named substance, the acetic 

 and oxalic acids being carried off by oxidation through the lungs, and the urea 

 being removed by the kidneys. It is some confirmation of this view, that acetic 

 acid has been found by Scherer in the juice of flesh. Inosinic acid, however, 

 would not appear to be one of the necessary products of the disintegration of 

 muscle ; for it is frequently absent altogether, and, when it is present, its quan- 

 tity is very variable. Two other organic acids have been observed by Liebig 

 in the juice of flesh, besides the lactic ( 48); but little is known of their com- 

 position. From his latest inquiries, however, it appears that the juice of flesh 

 immediately on being expressed has no acid reaction, but that this very speedily 

 presents itself on exposure of the fluid to the atmosphere ; from which it may 



1 This doctrine, advanced by Prof. Liebig in his important treatise on " The Chemistry 

 of Food," is a specimen of the absurdities into which even so eminent a Chemist may be 

 betrayed, when he abandons that path of purely chemical research in which he is approached 

 by few, to speculate upon a subject of which he is comparatively ignorant, and on which 

 the opinions of scientific Physiologists have a much higher claim to consideration. Both 

 Chemists and Physiologists, however, are now so generally in accordance with regard to 

 the excrementitious character of Creatine, that the original doctrine of Prof. Liebig will 

 probably be soon forgotten. 



