1867.] Extractive Matters of Urine, — Part I. 



85 



These experiments render it probable tbat the ordinary brown colouring- 

 matters formed by the action of acids on urine are in fact derivatives of in- 

 digo-blue, however little their properties may resemble those of the latter. 

 In some experiments, an account of which I presented a short time ago to 

 the Manchester Literary and Philosophical Society *, I obtained by the 

 direct action of alcohol, acetate of soda, and caustic soda on indigo- blue a 

 number of products, several of which bear a striking resemblance to 

 uromela7iine, as the brown pulverulent substance obtained by the action of 

 acids on urine has been called, and which differ in their properties from 

 indigo-blue quite as widely as that substance does. But into this part of 

 the subject I cannot enter further at present. 



The licjuid filtered from the insoluble matter formed by the action of 

 acids on urine I found to possess the property, after being made alkaline, of 

 dissolving oxide of copper and converting it into suboxide on being boiled. 

 This reaction, which had never been previously observed, I attributed to 

 the presence of glucose, which, together with the brown colouring-matters, 

 had been formed at the expense of the extractive matters. The correctness 

 of this inference has been doubted, since the same reaction may be pro- 

 duced by other substances as well as glucose ; but whether it be correct or 

 not, the fact remains, that normal urine free from sugar acquires the pro- 

 perty of reducing oxide of copper as soon as it has been boiled with the ad- 

 dition of a strong acid. The general conclusion to wdiich T was led by 

 these few experiments was, that there not only exists a great resemblance 

 between indican and the extractive matters of urine, as proved by the simi- 

 larity of their products of decomposition, but that they are also very pro- 

 bably in some way closely related as regards their composition and general 

 properties. In giving an account of my views on this subject I used these 

 words : — *' I think it is probable that the indigo-producing body will be 

 found, as regards its formation and composition, to occupy a place between 

 the substance of the tissues and the ordinary extractive matter of urine." 

 Though this may have appeared at the time when it was pronounced a 

 hasty conclusion, further research has only tended to confirm it. 



III. The colouring-matters occurring in normal urine, and to which the 

 usual colour of the secretion is due, have been less frequently submitted to 

 investigation than those which make their appearance only exceptionally, 

 or in consequence of some artificial process of decomposition. This cir- 

 cumstance may easily be accounted for. These substances are all amor- 

 phous and possess few characteristic properties ; hence their separation 

 from the other constituents of urine is attended with great difiiculties, and 

 has even been pronounced impossible. They are also compounds of very 

 little stabihty, as every one who has worked with them must have observed, 

 so much so that mere evaporation of the urine seems to produce a complete 

 change in their composition, as seen by the marked alteration of colour 

 which takes place during the process. Then it has been observed that 

 * Memoirs of the Society, 3rd series, vol. iii, p. 66. 



