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Mr. F. Kidd. 



oxidations by the oxygen of the atmosphere under ordinary conditions. 

 Intramolecular respiration was thought to be essentially the same as alcoholic 

 fermentation. There appeared, however, objections to Pfeffer's theory, 

 notably that the amount of C0 2 produced in anaerobic respiration was found 

 not to bear a definite relation to the amount of C0 2 produced in normal 

 respiration, that is to say a relation of one to three, as should be expected 

 from Pfeffer's view. Further, plant tissues did not appear to have the power 

 of oxidising alcohol. 



In 1903 this line of speculation received a renewed stimulus. Stoklasa and 

 Czerny reported the extraction of an enzyme from beetroots, potatoes, peas 

 and other plant tissues, and also from animal tissues such as the liver, heart, 

 lungs and kidney, which they termed zymase and which appeared quite 

 similar to Buchner's enzyme, extracted from yeast a few years previously. 

 Following these discoveries, attention was again turned to the study of intra- 

 molecular respiration, but in the result the proportion of carbon dioxide to 

 alcohol formed in anaerobic conditions could not be found to fulfil the 

 requirements of the theory which compared the processes of anaerobic carbon 

 dioxide production strictly to those of fermentation in the presence of zymase. 

 The amount of C0 2 produced generally exceeded the amount theoretically 

 required in relation to the alcohol formed. It was concluded that the CO2 

 evolved in anaerobic respiration arose in varying degrees from other sources 

 as well as from the action of zymase. 



At the present day, with the researches of Blackman, Palladin, Deleano, 

 and others, we have advanced to a more critical view of the various processes 

 underlying plant respiration. It has been recognised that under the general 

 heading of respiration we are dealing with the combined result of various 

 distinct processes. A leading distinction has been pointed out by Blackman 

 between that respiration on the one hand which involves the breakdown of 

 sugar, fat, or organic acid, which he has termed floating respiration, and on the 

 other hand the essential respiration of protoplasm. The present position of 

 research with regard to the mechanism of plant respiration appears to be that 

 we find ourselves faced with a complexity in time, on the one hand, in which 

 a chain of sequent reactions is involved and on the other hand with a 

 complexity in space in which various types of material are being simultane- 

 ously broken down along different paths. The present researches confirm 

 this conception. 



Section II. — Methods of Experiment. 



In these experiments, which have been directed to determine the influence 

 of carbon dioxide upon respiration, the general method adopted was as follows. 



