480 Professor TJiorpe [Feb. 15, 



their analogues and prototypes in inorganic chemistry. The con- 

 cluding words of the memoir strike in fact the key-note of the whole 

 investigation. " In once more reviewing and connecting together the 

 relations described in this paper, we find that they may be grouped 

 round a common nucleus which preserves intact its nature and com- 

 position in its associations with other bodies. This stability has 

 induced us to regard this nucleus as a kind of compound element, and 

 to propose for it the special name of benzoyl." 



A significant feature of the memoir was that each of the substances 

 described and correlated was the type of a group of bodies, some of 

 which were known, but of which the analogies and relations were 

 unthought of; others of these bodies had yet to be discovered, a 

 matter of little difGculty when the modes of their origin had been 

 indicated. The effect of this memoir on the chemical world was very 

 great. Berzelius indeed regarded it as the dawn of a new day in 

 vegetal chemistry, and proposed that the new radicle should be named 

 proin (from Trpwl, the beginning of day) or orthrin (from opOpos, day- 

 break. 



Wohler remained in Cassel nearly five years. In the autumn of 

 1835 died Stromeyer, Professor of Chemistry in the University of 

 Gottingen, and the choice as to his successor lay between Liebig and 

 Wohler. Eventually Wohler was selected, and he entered on his work 

 at Gottingen in the early part of 1836. He was succeeded at Cassel by 

 Bunsen, who was at that time " privat decent " at Gottingen. In the 

 October of 1836, Wohler was ready for fresh work, and he proposed to 

 Liebig to workout the singular origin of benzaldehyde (bitter almond 

 oil) from amygdalin under the influence of a nitrogenised ferment, 

 termed by Liebig and Wohler, emulsin. Amygdalin in presence of 

 water is decomposed into benzaldehyde, prussic acid, and sugar 

 (glucose). Both the emulsin and the amygdalin exist together in the 

 almonds, but are contained in separate cells and are only brought into 

 contact by the rupture of the cell-walls and the solvent action of the 

 water. Amygdalin was the prototype of a large and important group 

 of substances classed together as the glucosides. 



At the instigation of Wohler the friends again returned to the ques- 

 tion of the chemical nature of uric acid, and the memoir which they 

 published on this subject is of the profoundest interest not only to the 

 chemist but also to the physiologist. Uric acid, originally discovered 

 by Scheele, was shown in 1815 by William Prout, then a boy of nine- 

 teen, to be the main constituent of the solid excreta of reptiles ; other 

 chemists had succeeded in obtaining various derivatives from it, 

 indeed Prout himself had prepared from it the so-called purpuric 

 acid — a substance which years afterwards, as murexide, obtained a 

 transitory importance in the arts as a colouring matter. But nothing 

 was known concerning the constitution of the body or of its relations 

 to its derivatives until Wohler and Liebig attacked the problem. 

 The extraordinary mutability of uric acid, which had baffled and 



