484 BOTANICAL GAZETTE [june 



animal was due to an incapacitation of the red blood corpuscles, 

 which caused suffocation, a conclusion still generally accepted. 

 Geppert (3), and still later Vernon (id), who worked with animals, 

 found this same inhibitory effect of hydrocyanic acid on respiration. 

 They showed that if a lethal dose has not been given the organism 

 recovers completely; that is, if the organism is not killed it is not 

 injured in any way. Schroeder (9), using the fungus Aspergillus 

 niger, made a long series of determinations on the effect of potassium 

 cyanide on respiration. He confirmed the previous work and 

 emphasized the fact that, if cells were not exposed too long, recovery 

 was complete. He also did some work with ether, and decided that 

 the inhibition of respiration caused by treatment with this 

 anesthetic was quite different in character from inhibition caused by 

 treatment with cyanide. He characterized diminution of respira- 

 tory rate through treatment with ether as a secondary effect, 

 brought about by previous death of the tissue; while diminution 

 of respiratory rate through treatment with cyanide is a primary 

 effect, the cyanide directly inhibiting respiration and killing the 

 tissue. 



Mathews (5) has offered strong arguments favoring a contrary 

 view, namely, that hydrocyanic acid and anesthetics both act 

 primarily on the respiratory processes, each affecting these in 

 exactly the same manner. 



Another activity of cyanide, which has come into prominence in 

 recent years, is its role as an "enzyme paralyzer '' and more specifi- 

 cally its abihty to check certain chemical reactions carried on in the 

 laboratory. Bredig and Ikeda (i), also Loevenhart and Kastle 

 (4), have found that in the catalytic decomposition of hydrogen 

 peroxide the addition of a very small amount of potassium cyanide 

 completely stopped the reaction. They concluded that the cya- 

 nide was acting on the catalytic agent. Mathews and Walker 

 (6), who worked on the spontaneous oxidation of a very reactive 

 amino acid, cystein, found that a very small amount of potassium 

 cyanide checked this action. Their statement of the probable 

 explanation of this is interesting, since the same reasoning is equally 

 appKcable to other inhibitions of oxidation processes by cyanide. 

 "The proportion of cystein molecules in a condition to be oxidized 



