[Vol. 6 



72 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



itself, not its sodium salt nor its hydrochloride. Work with 

 the acid would enable one to work with the substrate much 

 nearer the neutral point than would have been possible other- 

 wise, thus avoiding interfering conditions due to hydrogen 

 ion concentrations other than that of water. 



The literature on the oxidases in general, including most of 

 the papers on the tyrosinase reaction, has been so excellently 

 reviewed by Behrens ('07), Kastle ('10), Clark ('10, '11), 

 Bach ('13), Rose ('17), and probably Schweizer (16), that 

 there is little need to add to the reviews already published, 

 although certain works will be discussed in some detail in 

 connection with the methods employed and the results ob- 

 tained. 



I wish at this point to acknowledge indebtedness to those 



who have so kindly offered suggestions as the problem has 

 developed. Thus, I wish to thank the Missouri Botanical 

 Garden and the Medical School of Washington University 

 for the use of library and laboratory facilities; Dr. B. M. 

 Duggar, under whose supervision the work has been done and 

 without whose advice it would have been difficult indeed ; Dr. 

 P. A. Shaffer, Dr. Lucien J. Morris, and Dr. E. R. Allen, all 

 of the Medical School, for valuable suggestions regarding 

 chemical procedures. 



Methods 



Extraction and precipitation of the enzyme— Of the many 

 methods used for the extraction of the enzyme and its sep- 

 aration from laccase, fractional precipitation has been most 

 widely used (Chodat, '10, Wohlgemuth, 13). The methods 

 previously reported by Bertrand ('96), Bach ('08, 10), 

 Chodat and Staub ('07), Bertrand and Muttermilch ('07), 

 von Fiirth and Schneider ('01), and von Fiirth and Jeru- 

 salem ('07), were tried out, but for the conditions under 

 which I worked none proved especially satisfactory. I was 

 unable to filter rapidly enough to prevent the inactivation of 

 the enzyme by its long contact with the precipitant. The use 

 of the sap before precipitation was tried, but this was not 

 very satisfactory, since it necessitated diluting the tyrosin 



