1919] 



DODGE — TYROSINASE REACTION 73 



and thus adding to the already great difficulties of analysis, 

 owing to the extreme insolubility of the product. Therefore 

 in the work with tyrosin, the dried fungous flour was added 

 directly to the substrate, toluol added, and the mixture left 

 to extract the enzyme and the enzyme to react with the tyrosin, 

 a general method used by Zeller ( '17 ) . In work with phenyl- 

 alanin and other amino-acids which have a much greater 

 solubility than tyrosin, the calculated amount of fungous 

 flour was extracted with chloroform water for 24 hours, 

 filtered, and the filtrate mixed with an equal volume of N/250 

 of the amino-acid used, thus making the final concentration 

 N/500, approximately that of a saturated solution of tyrosin, 

 and allowing the same chemical procedures to be followed. 



The fungi were brought in from the collecting trip, cut up 

 by a vegetable slicer into pieces about 1-2 mm. thick, spread 

 out on the table top, and allowed to dry at room temperature, 

 either with or without an electric fan to keep the air in circu- 

 lation. Some, such as Daedalea confragosa, which are cori- 

 aceous, were treated alternately with two or three volumes 

 of 95 per cent alcohol and acetone until most of the water 

 was removed from the tissues, then dehydrated with absolute 

 alcohol and dried as above, in order to facilitate grinding by 

 rendering the tissue more brittle. The fungous "chips," 

 resembling the potato chips of commerce, were ground in a 

 large mill to about the fineness of wheat bran. This was sifted 

 through an 80-mesh sieve and the powder stored in 

 bottles, which were sealed with paraffin until needed. The 

 bran was likewise stored in bottles awaiting a chemical study. 

 The fungi were obtained in the fall of 1916, except the mate- 

 rial of Polyporus sulphureus, of which about 10 kilos fresh 

 weight were obtained in the fall of 1917. 



Methods previously employed in the study of the tyrosinase 

 reaction. — Most of the work done on the tyrosinase reaction 

 has been qualitative, where the enzyme has been allowed to 

 come into contact with the substrate, and the resulting colors 



noted. 

 Five kinds of quantitative methods have been used in the 



study of this reaction. Von Fiirth and Jerusalem ('07) have 



