4 On the Colouring and Extractive Matters of Urine. [Jan. 18, 



composition. Indeed the first step which he thought it necessary to take, 

 before proceeding with the investigation at all, was to ascertain whether 

 these extractive matters are bodies of a definite chemical nature, or 

 whether they are merely accidental , mixtures of various excrementitious 

 substances thrown out by the system, and diifering in their nature accord- 

 ing to circumstances. In order to arrive at a positive conclusion on this 

 point, several series of experiments were undertaken. The method devised 

 for the purpose of separating the extractive matters from the other con- 

 stituents of urine, and obtaining them in a state of purity, presents few 

 features of novelty as compared with those previously employed. The ex- 

 periments necessarily occupied a considerable time, since the author con- 

 sidered it essential, in order to avoid decomposition, to evaporate all the 

 solutions at the ordinary temperature by means of a current of air. The 

 certainty of the conclusions arrived at afforded, however, ample compen- 

 sation for the loss of time and additional labour thus occasioned. The 

 composition of the extractive matters was determined by analyzing their 

 lead compounds, since the substances themselves cannot be obtained in a 

 state fit for analysis. 



From the experiments described in this part of his paper the author 

 thinks he is justified in drawing the following conclusions : — 



1. Human urine contains at least two peculiar and distinct extractive 

 matters, one of which is soluble in alcohol and ether, while the other is 

 soluble in alcohol, but insoluble in ether. The existence of an extractive 

 matter insoluble both in alcohol and in ether is extremely doubtful. 



2. The composition of these extractive matters varies slightly, without 

 any corresponding difference in their appearance and properties being per- 

 ceptible ; but these variations are not due to any difference in the quality 

 of the urine or the source whence it was derived, but rather to the de- 

 composition which takes place during the process employed in their prepa- 

 ration, and which cannot be entirely avoided. 



3. "When quite pure, the extracti\^e matter soluble in alcohol and ether 

 has a composition corresponding with the formula Cgg Hj^ NOg^, while that 

 of the extractive matter soluble in alcohol but insoluble in ether is ex- 

 pressed by the formula Cgg H^^ NOgg. 



January 18, 1865. 



Lieutenant- General SABINE, President, in the Chair. 



The President stated that Dr. William Bird Herapath, who by reason 

 of non-payment of his annual contribution ceased to be a Fellow of the 

 Society at the last Anniversary, had applied for readmission. The Statute 

 relating to the case was read, and, in accordance therewith, notice was 

 given that the question of Dr. Herapath's readmission would be put to 

 thie vote at the next meeting. 



The following communications were read : — 



