EFFECT OF POISONS 103 



dead tissues : quinine hydrochloride in a "09 per cent solution 

 gave a threefold increase in the output of carbon dioxide from 

 living stem apices of the broad bean but was without effect on 

 killed apices ; a dose of I per cent gave the same increased 

 yield from the live stems and reduced the evolution of carbon 

 dioxide from the dead. Arbutin in a I to 2 per cent solution 

 depressed the respiration of wheat seedlings to a greater degree 

 in dead than in live seedlings. Palladin looks upon the in- 

 creased output of carbon dioxide in living tissues following 

 poisoning as being due to the reaction of the protoplasm 

 against the poison employed. In such living tissues the poison 

 does not result in a change in the amount of peroxide ; in 

 killed tissues, on the other hand, the decreased output of carbon 

 dioxide is accompanied by a reduction in the amount of per- 

 oxidase, which presumably is destroyed by the poison.* 



With regard to that aspect of respiration associated with 

 enzymes more directly connected with the protoplasm, Pal- 

 ladin f adopts the view not uncommonly held J that the pro- 

 cess is anaerobic and is essentially the same phenomenon as 

 alcoholic fermentation. It has been mentioned that a supply 

 of respirable material, of which sugar is a prominent material, is 

 an important conditioning factor governing the respiration rate. 



Of the enzymes able to effect the decomposition of sugar, 

 zymase is the most prominent ; to what extent other enzymes, 

 more especially those associated with respiration in the narrower 

 sense, are operative is a subject for further investigation. 

 Zymase has been described as being of widespread occurrence. 

 The successive stages in the reduction are not known, where- 

 fore agreement regarding the nature of the complete reaction 

 has not been reached. Palladin considers that there is in the 

 first instance a reaction between the sugar and water which 

 leads to the formation of carbon dioxide, which is thus of 

 anaerobic origin, and hydrogen. But hydrogen as such is not 

 one of the gaseous waste products, wherefore it must be fixed 

 as quickly as it is formed. Here, Palladin's respiration pig- 

 ments are operative : they exist in the plant in the form of 



* Palladin : " Jahrb. Wiss. Bot.," 1910, 47, 431. 

 f Palladin " Zeit. Garungs. Physiol.," 1912, I, 91. : 



JBach and Batelli : " Compt. rend.," 1903, 136, 1357; Godlewski and 

 Polzeniusz : " Bull. Int. Acad. Sci. Cracovie," 1897, 267; 1901, 277. 



