OXIDASES OR OXIDISING ENZYMES. 255 



the mixture of it with urushic acid undergoes no change. 

 The nature of this nitrogenous constituent has not been 

 clearly established, but it seems to differ from the ordinary 

 proteids by containing a much smaller proportion of nitrogen. 

 Yoshida's analysis of it gives C63'44H7'4i N4/01 022-94 

 Ash 1 '2 in 100 parts. 



From his experiments Yoshida comes to the conclusion 

 that urushi juice consists essentially of four substances, 

 viz., urushic acid, gum, water and a peculiar enzymic matter. 

 The phenomenon of its drying is due to the oxidation of 

 urushic acid C 14 H 18 O s into oxyurushic acid C 14 H ]s 3 , which 

 takes place by the aid of the enzyme in the presence of 

 oxygen and moisture. 



He supports this conclusion by two series of experi- 

 ments which may be quoted here. 



A small quantity of the original juice was put into a 

 covered beaker, and subjected to the regulated heat of a 

 water-bath, the water lost by evaporation being subse- 

 quently restored. The heating was carried to different 

 temperatures and subsequently the heated juice was thinly 

 spread over a glass plate and left to dry in a box, the 

 air in which was kept moist. In each experiment the 

 juice was heated for three and a half to four hours and 

 the drying was allowed to take place at a temperature 

 of 20° C. 



The results were as follows : — 



In the second series of experiments he found that un- 

 less moisture was present the latex did not dry ; that in 

 moist air it dried in four hours, in moist oxygen in two 

 hours ; in moist hydrogen or nitrogen it took thirty-six 

 hours and in moist CG 2 it was dry only after two days' 

 exposure. 



It follows from these experiments that the enzyme. 



