president's address. 23 



decoDipositions and incite combinations under the conditions 

 favourable to the continued life of animals and plants. We sow 

 a wheat-seed, presumed to contain minute amounts of a number 

 of these ferments, and from the fully grown wheat-plant we can 

 obtain a greater degree of ferment-activity. The powers of these 

 ferments do not differ from those possessed by lifeless chemical 

 substances under certain conditions. Most chemical substances 

 appear capable of bringing about decompositions or combinations 

 in other bodies in the same way and under analogous circum- 

 stances as do the ferments from living tissues. When acting in 

 this manner, these substances are called catalysts. Chemists do 

 not, however, suppose that platinum black inciting the union of 

 hydi-ogen with oxygen contains some unknown ferment. The 

 sulphuric acid which brings about the decomposition of cane 

 sugar into glucose and hevulose is presumed to be chemically pure 

 sulphuric acid. Chemists are beginning to recognise that cata- 

 lysts are not a group of substances possessed of these special 

 qualities, but that many, if not all, chemical substances can act 

 as catalysts under particular conditions. Evidence is accumu- 

 lating to show that it is on the arrangement of the particles, 

 molecules, or whatever we may call the minute masses of the 

 substance, that the capacity to act as a catalyst dej^ends. The 

 physical state of a substance rather than the kind of matter of 

 which it is formed, confers catalytic activity. There appears to 

 be no reason to infer that the catalytic action of the extracellular 

 and endocellular ferments found in animal and vegetable tissues 

 has a different basis. I have always been impressed by the fact 

 that the powei- of an extract of an animal or vegetable extract 

 to act as a ferment was abolished by those agencies which pro- 

 foundly alter the colloidal state of proteins and lipoids. The 

 attempts to identify the unorganised ferments as a special class 

 of chemical substances have invariably ended in failure. May 

 we not look for better progress along other lines of investigation? 

 The study of the position of the particles composing inorganic 

 crystals has given us an insight into the arrangement of the 

 atoms or ultimate particles in the molecule. The crystals of 



