iqiq] rose— blister CANKER 12 1 



reagent was followed by a marked increase in oxidation. For 

 example, in table VIII it is seen that from the ninth to the twenty- 

 sixth day oxidation in apparatus 8, containing pyrogallol and bark 

 extract, showed an increase of only o .47 cm., while tubes 10 and 11, 

 also containing pyrogallol and bark extract to which benzidine 

 solution was added later, showed an increase of i .95 and i .34 cm. 

 respectively. Equally marked excess over the check was obtained 

 when solid pyrogallol or soHd benzidine was added. One might 

 infer that the oxygen admitted, when the tubes were opened to 

 introduce reagents, increased oxidation, but this effect could hardly 

 account for the difference observed. Bunzell states that exhaus- 

 tion of oxygen is not the hmiting factor, and experiments by the 

 writer have shown that, when a fresh oxygen supply is allowed to 

 enter the apparatus, the subsequent increase in oxidation is small. 



The fact that after oxidation ends it can be started afresh 

 by the addition of fresh plant material or of fresh oxidase reagent 

 suggests that the equilibrium reached is a false one, like the third 

 case described by Hober (23, p. 671), in which a reaction product 

 of the catalytic reaction brings about equiUbrium by an inactiva- 

 tion of the catalyzer. A test for this condition according to Hober 

 is that reaction begins again when more catalyzer is added, as in 

 the case of the hydrolysis of amygdalin by emulsin. The similarity 

 between the two reactions, however, does not prove that the oxida- 

 tion catalyst is an enzyme, for it may be non-enzymic in nature 

 and still be inactivated by the products of the catalytic reaction. 



An idea of the nature of the oxidase reaction was obtained by 

 testing some of the data by the formula for unimolecular reaction, 



k= log. . In these calculations the total amount of oxida- 



/ a—x 



tion (mercury rise) at the end of the shaking period was assumed 

 for the value of a, and the amount of oxidation at the end of each 

 15-minute interval for the value of x. The figures which should 

 be used, of course, are the total amount of pyrogallol at the begin- 

 ning of the experiment and the amount oxidized at the end of each 

 15-minute interval, but such figures would be difficult to obtain. 

 The writer sees no reason why the values used for a and x do not 

 truly represent the course of the reduction. 



