102 RESPIRATION 



with the protoplasm and which may or may not be found in 

 the expressed sap ; that produced directly from the protoplasm 

 under stimulation such as wounding, which aspect of the sub- 

 ject has already been considered ; and that produced as a 

 result of oxidase activity.* With respect to the production of 

 carbon dioxide by oxidase enzymes, Palladin accepts Bach and 

 Chodat's hypothesis regarding the constitution of these en- 

 zymes and considers that this phase in respiration depends on 

 the presence of an oxidizable substance which under the action 

 of the oxygenase yields an organic peroxide which transfers 

 oxygen, when stimulated by the peroxidase. 



Palladin further accepts Bach and Chodat's opinion that 

 oxygenases, if they exist, are very unstable and are quickly 

 used up ; it is for this reason that the presence of oxygenases 

 is difficult to demonstrate. This idea of the action of oxidases 

 in respiration is bound up with the tenability of Bach and 

 Chodat's opinion regarding these bodies. There is, however, 

 much to be said for the thesis that respiration is not neces- 

 sarily one single operation but consists of at least two, of 

 which one is the oxidation of substances by enzymes only 

 indirectly related to the protoplasm and is not therefore a 

 concomitant of life. Palladin and Kostytschev, for instance, 

 showed that germinated peas which had been killed without 

 injury to the enzymes may give off more carbon dioxide than 

 during life, and so also may the bulb of an onion, killed by 

 exposure to a temperature of - 20 C. on thawing, although 

 in this instance the amount of oxygen absorbed is less than in 

 the living condition. Haasf found that plants of Laminaria 

 poisoned by various substances such as ethyl bromide, acetone, 

 and alcohol first showed a rise in respiration followed by a 

 smooth decline to zero ; at the death point the evolution of 

 carbon dioxide was not markedly smaller, and it may be con- 

 siderably greater, than the normal rate in living tissue. But 

 this post mortem respiration is not shown in all instances : 

 Palladin observed that the evolution of carbon dioxide from 

 finely ground wheat is less than from the living intact grains. 



He also made a comparative study of the effects of various 

 poisons on the evolution of carbon dioxide from living and 



* Palladin : " Ber. deut. hot. Gesells.," 1905, 23, 340 ; 1906, 24, 97. 

 f Haas : " Bot. Gas.," 1919, 67, 347. 



