1866.] and Extractive Matters of Urine, 3 



niiuation of the composition of the brown pulverulent substance resulting 

 from the action of strong acids on urine, the author infers that it may be 

 expressed by the formula C,^ NO^, which is also that of anthraniiic 

 acid, a product of decomposition of indigo-blue. All these products (the 

 resin, the brown pulverulent substance which has received the name of 

 uromelanine, and the glucose) are, in the author's opinion, derived from the 

 extractive matter of urine, which by decomposition with acids yields these 

 and perhaps other products. The conclusion formerly arrived at by the 

 author, viz. " 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," is one which fur- 

 ther research, as the author thinks, has only tended to confirm. 



The urinary colouring-matters belonging to the third class, consisting of 

 those to which the ordinary colour of the secretion is due, have been less fre- 

 quently submitted to investigation than those which make their appearance 

 only exceptionally or in consequence of some artificial process of decompo- 

 sition. This circumstance may easily be accounted for. These so-called co- 

 louring-matters are all amorphous, and possess few characteristic properties ; 

 hence their separation from the other constituents of urine is attended with 

 great difficulties, and has even been pronounced impossible. They are also 

 compounds of very little stability — so much so that mere evaporation of 

 the urine seems to produce a complete change in their composition, as is seen 

 by the marked change of colour which takes place during the process. 

 The opinions entertained on the subject by the earlier chemists, such as 

 Fourcroy and Vauquelin and Proust, having been referred to, the author 

 gives a short account of the experiments of Berzelius, Duvernoy, Lehmann, 

 Scherer, Harley, Tichborne, and Thudichum. Berzelius and Lehmann 

 both found the substance to which healthy urine owes its colour to be 

 completely soluble in water. Subsequently, however, most of the attempts 

 which were m.ade to isolate the colouring-matter of urine ended in the 

 separation of substances quite insoluble in water. These must in all cases 

 have been products of decomposition ; for the author considers it quite cer- 

 tain that the colouring-matters derived from urine which are insoluble in 

 water are not contained as such in the secretion, provided the latter is in 

 its normally acid state. 



Having concluded his summary of the results obtained in previous re- 

 searches, the author proceeds to give an account of his own experiments. 

 Before doing so, he states that he shall apply the term " colouring-matter" 

 to those bodies only which, occurring naturally in urine or else formed by 

 processes of decomposition, are insoluble or not easily soluble in water, 

 while the substances easily soluble in water to which the colour of normal 

 urine is due, he shall continue for the present to call " extractive matters." 

 The extractive matters being, in the author's opinion, the source whence 

 most of the colouring-matters of urine are derived, he resolved to com- 

 mence the investigation by a careful examination of their properties and 



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