562 Dr. Armstrong and Prof. Armstrong. Studies on [June 13, 



those relating to the interactions of water, interactions which it is now 

 generally admitted are often of great complexity. 



Definition of an Enzyme. — At the outset we are met by the difficulty of 

 denning an enzyme. The state of opinion is well brought out in the 

 opening lines of the recently published English edition of Euler's ' General 

 Chemistry of the Enzymes ' : — 



" The name enzyme is given to animal or vegetable substances . . . . 

 which are able to accelerate chemical reactions. The term enzyme is thus 

 included in the much more general term catalyst. By catalyst we under- 

 stand a substance which, without being required by the accelerated reaction 

 or appearing among the final products, alters the velocity with which a 

 chemical system strives to attain its final condition." 



As one of us is responsible for the introduction of the word catalyst* we 

 may be permitted to consider the significance of the term. 



Catalysis. — It is noteworthy that the conception of catalysis, first 

 enunciated by him in 1835, is discussed by Berzelius in his celebrated 

 ' Jahresbericht ' (vol. 15, p. 237), under the heading " Pflanzenchemie," in a 

 section to which is attached the significant explanatory marginal note — 

 " Some ideas on a hitherto unnoticed force active in living Nature in the 

 formation of organic compounds." 



At the outset, Berzelius refers to the difficulty of explaining the complex 

 phenomena of organic life with the aid of the conceptions up to that 

 time derived from the study of inorganic phenomena. He then draws 

 attention to the discovery of a series of changes in which the agent 

 appeared to take no permanent part in the change but was ultimately 

 recovered unaltered in amount. 



Thus he refers in succession to the formation of grape sugar from starch 

 by means of dilute acids (Kirchof — 1814) : to Thenard's discovery of 

 hydrogen peroxide, a substance which is readily resolved into oxygen and 

 water : to Humphry Davy's observations on the effect heated platinum has 

 in inducing the oxidation of the vapour of alcohol or ether : to Edmund 

 Davy's discovery of platinum black, a substance which induces oxidation at 

 ordinary temperatures : to the use that Doebereiner made of this discovery 

 in constructing his well-known lamp : to Dulong and Thenard's observa- 

 tions on induced oxidation, showing that not only the platinum metals but 

 also gold, silver and even glass could produce similar effects if sufficiently 



* ' Report of the British Association,' 1885, p. 953. We venture to deprecate the use 

 of the expression " to catalyse " — hoth because it appears to us to lack euphony and to be 

 unnecessary if not undesirable ; for similar reasons, we regard catalyst as preferable to 

 catalyser. 



