iqiq] rose— blister CANKER 131 



The difference in the effect of gelatine and of gum arabic on 

 oxidation by healthy bark may depend on differences in the col- 

 loidal solutions they form. An artificial oxidase prepared by 

 Dony-Henault (18) from manganese formate, sodium bicarbonate, 

 and gum arabic could be destroyed by heat; but one prepared by 

 Trillat (33) from albumin and manganese could not be so 

 destroyed. Bayliss (6, p. 585) thinks the difference here "clearly 

 depends on the nature of the emulsion colloid in association with 

 the metal." On the other hand, what little increase in oxidation 

 gum arabic produces may be due to an oxidase naturally present in 

 it (BouRQUELOT 7), although an experiment designed to test this 

 question gave negative results. One per cent gum arabic plus 

 I per cent pyrogallol, and pyrogallol alone, were placed in separate 

 oxidase tubes and shaken twice during each 24 hours. At the end 

 of 3 days the mercury rise was 0.32 cm. in the first case and 

 o . 20 cm. in the second, a difference almost within the limits of 

 error in reading the manometers. 



The data given in table XIX show that when the precipitate 

 is collected in 2 fractions, these fractions have a greater oxidase 

 activity if combined than if used separately. This condition seems 

 to be about the same as that described by Bach and Chodat (4) 

 for Lactarius vellereus. They found that by the fractional pre- 

 cipitation of an aqueous solution of the oxidase of this fungus, by 

 alcohol, 2 fractions could be obtained possessing markedly different 

 properties. The first of these was almost insoluble in 40 per cent 

 alcohol and had the properties of a weak oxidase; the second was 

 soluble in 40 per cent alcohol but insoluble in pure alcohol and had 

 no oxidizing powers. This fraction, however, was found to impart 

 greater activity to hydrogen peroxide as an oxidizing agent; it 

 was also found to increase markedly the oxidizing powers of the 

 first fraction. The chief difference between this situation and 

 that found in the work with apple bark is that in the latter 

 case the first fraction has more than a weak oxidase activity, 

 while the second, possibly because of incomplete separation of 

 the fractions, is not entirely without it. No tests have been 

 made of the behavior of the second fraction toward hydrogen 

 peroxide. 



