3 02 SCIENCE PROGRESS 



enzymes, since there is a proportionality between the amount 

 of enzyme and the total amount of change produced. This fact 

 is probably to be explained by the disappearance of the enzyme 

 during the reaction. A similar state of affairs is, indeed, to be 

 seen in the case of trypsin, though in a less marked degree. It 

 is found that small quantities of this enzyme will not effect the 

 same amount of hydrolysis as larger quantities, even when 

 allowed a very long time for the action. Experiment shows that 

 trypsin does disappear slowly even in the presence of substrate 

 or products. 



Ostwald has insisted that, in order that the formation of an 

 intermediate compound should be regarded as an adequate 

 explanation, it is necessary to show that the two reactions, forma- 

 tion of intermediate compound and splitting-up of this compound, 

 taken together progress at a velocity greater than that of the 

 reaction without the presence of the catalyst. This proof has 

 actually been afforded by Brode. When hydrogen peroxide acts 

 upon hydriodic acid, this latter is decomposed at a certain rate, 

 which rate is greatly accelerated by the presence of a trace of 

 molybdic acid. Now Brode has been able to show that per- 

 molybdic acids are formed by action of the peroxide on molybdic 

 acid and that these permolybdic acids, themselves produced 

 at a considerable velocity, react on the hydriodic acid with very 

 great velocity, molybdic acid being formed again, ready for a 

 further activity. These two reactions, then, together progress 

 at a greater rate than the action of the peroxide by itself upon 

 the hydriodic acid. 



When we consider the extraordinarily minute concentration 

 in which enzymes exert their activity, there seems some justi- 

 fication for such a view as that of Arthus and de Jager — viz. 

 that the properties known as those of enzymes are not associated 

 with definite chemical individuals, but may be conferred, to 

 a greater or less degree, on various kinds of bodies. In the 

 process of purification of certain enzymes solutions have been 

 obtained which, while very active, contain only an infinitesimal 

 amount of solid matter. On the other hand Brode has shown 

 that, in the reaction above described, the presence of i gram 

 molecule of molybdic acid dissolved in 31,000,000 litres of water 

 is capable of obvious catalytic action. In this case the catalyst 

 is a definite chemical compound. 



Space will not allow of the discussion of other theories of 



