18G7.] On the Colourhig and EoDtractive Matters of Urine, 73 



I. ^' On the Colouring and Extractive Matters of Urine/-' — Part I. 

 By Edward Schunck^ E.U.S. Received June 29^ 1865''^ 



Of all the animal secretions urine is undoubtedly one of the most 

 important. Its varying properties, in health as well as in disease, the 

 frequency with which it is emitted, and the consequent faciUty with which 

 it may be submitted to examination, render it invaluable to the physiolo- 

 gist and pathologist as a means of throwing light on the processes, either 

 healthy or morbid, going on within the body. Its study has therefore 

 engaged the attention of physicians since the earliest times, and of chemists 

 from the period when chemical analysis was first employed in the exami- 

 nation of natural objects. Notwithstanding the labour bestowed on the 

 subject by many eminent men during the past sixty years, it is still, how- 

 ever, far from being exhausted. There are, indeed, portions of the 

 chemistry of urine concerning which our ignorance is almost complete. 

 It is one of these obscurer parts of the subject that I have endeavoured to 

 clear up, and I hope to succeed in showing that I have added at least a 

 few facts to the sum of our previous knowledge. 



Of all the properties of urine none is more obvious, even to the ordinary 

 observer, than its colour. The variations in tint which it exhibits at 

 different times are striking, even to the unpractised eye, and they some- 

 times serve as important indications to the physician. Nevertheless con- 

 cerning the chemical nature of the substances to which its colour is due 

 very little is known. Our ignorance on this subject may be ascribed to 

 various causes. In the first place, some of these substances occur in the 

 urine only occasionally, and in very minute quantities, so that the prepa- 

 ration of a quantity sufficient for chemical examination becomes difficult 

 and even impossible, especially when the urine containing them is not 

 abundant. Secondly, it has been found that some of them are very easily 

 decomposed, so much so that the mere heat required for the evaporation 

 of the urine seems to be sufficient to effect a change in their properties 

 and composition. It therefore becomes doubtful, after a long process has 

 been gone through for the purpose of separating any colouring-matter from 

 the other constituents of the urine (a process in which, perhaps, strong- 

 chemical reagents have been employed), whether the substance procured 

 was originally contained as such in the urine, or is not rather a product 

 resulting from the decomposition of some other substance or substances. 

 Thirdly, several of the bodies colouring the urhie possess very few charac- 

 teristic properties. They are amorphous and syrup-like, and they retain 

 water with so much pertinacity that on attempting to dry them they 

 undergo decomposition. Neither their compounds nor their products of 

 decomposition exhibit any distinguishing characteristics. They belong to 

 a class on which, for want of a better, the name extractive matter has been 



Eead January 11, 18G6 : see Abstract, vol. xv. p. 1. 

 VOL. XVI. G 



