THE PLANT OXIDASES 249 



OXIDATION BY CATALYSTS OF INORGANIC ORIGIN. 



Since the foregoing chapter was written, a lengthy 

 paper by Ewart (1914) has appeared, in which the action 

 of oxidases is compared with that of inorganic catalysts. 

 Ewart emphasizes the importance of the action of other 

 salts upon the activity of such oxidizing systems. These 

 may act as inhibitors or sensitizers. He also believes that 

 " there is no justification for the use of such terms as 

 ' peroxidase,' ' katalase,' ' cenoxydase,' or ' tyrosinase,' to 

 indicate specific substances, ferments, or groups of fer- 

 ments. The ' tyrosinase ' of the potato is also a ' kata- 

 lase,' a c peroxidase,' a ' pyrogallase,' a ' hydroquinonase,' 

 and a ' paraphenylendiaminase.' It is, however, per- 

 missible to use such terms as ' katalase action ' or ' per- 

 oxidase action,' and such names as ' laccase,' ' russulase,' 

 1 potatase,' ' carrotase,' etc., as temporary names to 

 indicate the origin of the substances whose chemical 

 nature is yet unknown. Comparison with metallic oxidases 

 shows that we are not even on safe ground in assuming 

 the existence of specifically distinct classes of plant oxi- 

 dases, such as phenolases, aminoxidases, and iodoxidases." 



With much of the above sweeping criticism of previous 

 work the present writer is in disagreement. Moreover, it 

 appears to him that a number of Ewart's observations are 

 open to other interpretations. 



The action of oxidizing salts upon guaiacum resin and 

 other oxidase reagents has formed the subject of a large 

 number of papers, and, in addition to a few mentioned by 

 Ewart, the following may be noticed: Bourquelot and 

 Bougault (1897), Breteau (1898), Wolff (1908), Cushny 

 (1908), and Alsberg (1908), as well as Kastle's (1910) 

 monograph. The extraordinary sensitiveness of guaiacum 

 to the presence of copper is such that the water distilled 



