98 PHYSIOLOGY OF ALIMENTATION. 



days the velocity constant had fallen lower still to 0.011. 

 We are familiar with this same inactivation in the case of 

 the true ferments, and it is not impossible that that which 

 causes the platinumsol to become inactive, namely, a pre- 

 cipitation of the colloidal par icles/lies at the basis of the 

 inactivation of the true ferments also. 



Poisons, the action of which upon organic ferments is more 

 or less characteristic and striking, show this same action 

 when brought in contact with inorganic ferments. The 

 physiological action of hydrocyanic acid finds its explana- 

 tion in its power to interfere with the oxidizing ferments 

 of the cell. When added in even exceedingly minute traces 

 to oxidizing (and other) ferments it reduces their action to a 

 point where it can scarcely be recognized. The addition of 

 hydrocyanic acid to platinumsol reduces its action upon hydro- 

 gen peroxide in the same striking way, for the presence of 

 0.0014 milligram hydrocyanic acid in a liter of the colloidal 

 platinum solution reduces its action one-half. Hydrogen 

 sulphide, which also has a powerful action in inhibiting the 

 activity of organic ferments, shows the same behavior when 

 added to the colloidal solutions of the noble metals. The 6'rcter 

 in which the poisons, ferments, and hydrogen peroxide are 

 put together is not without influence upon the extent of the 

 inhibition produced. The fact is therefore of interest that 

 the order which is most effective in reducing the action of 

 an organic ferment is also the most effective when an in- 

 organic ferment is dealt with. 



