IN ANIMAL TISSUES. — HAREIS. 271 



quite white; twenty four hours later the tube in (b) was 

 white. The behaviour of tissue-juice is compatible with its 

 active constituent being an enzyme. 



3. As judged by the Pozzi-Escot test, a reducing ferment 

 is present in certain tissues; for pieces of tissue, but better 

 their juices, decompose pure H202without affecting a mixture 

 of guaiacum and H2O2. 



That the press juice, for instance of liver, is more active 

 than pieces of liver is in accordance with the findings of other 

 workers on ferments. J. J. R. MacLeod(2'^)noticed this in the 

 case of glycogenase, an undoubted endo-enzyme. 



4. The reducing action is accelerated or augumented by 

 the presence of alkaline salts of the tissues, which behave as 

 adjuvants. Professor Irvine and I(")concluded that reduc- 

 tase acted after the manner of pyrogallol, an organic reducer, 

 in an alkaline medium. 



5. In my recent work(2i)on the action of protoplasmic 

 poisons on reductase, I found that the acidity (concentration 

 of H ions) was a more profound inhibitant of the reducing 

 power than was toxicity. Concentration of H ions is well 

 known as an inhibitant of the activity of certain enzymes; to 

 this reductase would not form any exception. 



The fact that reductase is not totally inactivated .by 

 certain virulent protoplasmic poisons — chloroform, sodium 

 fluoride, nitrobenzene, formalin — makes reductase comparable 

 with the ferment in the laurel leaf studied by Dr. Waller(^^). 

 Chloroform was found to kill the leaf, but to set free an enzyme 

 which liberated HCN. 



6. As a ferment, reductase is pretty easily inactivated by 

 drying the juice in vacuo at 15°C and by precipitation from 

 juice by alsolute alcohol. As might be expected, drying and 

 alcohol injure it less in tissues than in press-juice. 



It clings with considerable tenacity to the cell-proteins, 

 which evidently guard it from inactivation by heat, by drying 

 and by alcohol. 



