VELOCITY OF REACTION 185 



the observations of Henri, Horace Brown and Glendinning, E. F. 

 Armstrong, and Bayliss that we began to understand the results, 

 and so bring the different observations into accord with one another. 

 O'Sullivan and Tompson were the first observers who studied 

 the velocity of action of an enzyme quantitatively throughout the 

 course of the reaction. 1 They employed the action of invertase on 

 cane sugar, and found that the reaction was mono-molecular, 

 obeying the mass action law, and giving a logarithmic curve. 

 Henri, however, who later worked at the same subject, found 

 that the value of the constant K, derived from their figures, by 



1 a 



using the formula deduced above, K=- log , did not remain 



* a 3/ 



quite constant throughout the reaction, but slowly increased in 

 value in the ratio, for example, of 298 near the beginning to 332 

 near the close of the reaction, thus showing that the velocity of 

 reaction only approximated to the logarithmic law. 



Tammann, in a series of researches, investigated not only the 

 action of invertase on cane sugar, but of emulsin on different gluco- 

 sides (salicin, amygdalin, arbutin, a3sculin), and found that the 

 reaction never proceeded to completion. He observed that the 

 velocity of reaction was retarded in increasing amount by the 

 presence of the products of reaction as these accumulated in 

 solution. The percentage which remained unconverted varied 

 with the temperature, the concentration of ferment, and the con- 

 centration of substratum. Increasing the temperature caused the 

 reaction after it had come to rest at the lower temperature to 

 recommence and proceed farther towards completion. With a 

 constant quantity of enzyme (emulsin) increased concentration of 

 substratum (amygdalin) increased the total quantity converted, 

 although not proportionately, the percentage conversion being 

 diminished; also, addition of substratum after the reaction had 

 ceased caused a fresh quantity to be converted. 



Removal of the products of conversion also had the effect of 

 causing conversion of further quantities. This last result is con- 

 firmed by other observers. 



1 That is to say, the progress of the reaction when a definite amount of 

 enzyme had been added initially; the effects of variation in amount of enzyme 

 acting for equal times had previously been studied by Briicke, Schiitz, and 

 others. 



