MECHANISM OF RESPIRATION ioT 



washing with mercuric chloride, in sterile conditions in a 

 sugar solution in the absence of oxygen. In other experi- 

 ments the seeds or seedlings were coarsely grown and suspended 

 in the nutrient solution, with all precautions against bacterial 

 activity, in anaerobic conditions. It was found that alcohol 

 was produced together with some acetaldehyde ; the addition 

 of calcium sulphite led to a considerable increase in the amount 

 of acetaldehyde. Klein and Pirschle * established acetic alde- 

 hyde as an intermediate product in the respiration of cereals 

 and pulses, and Pirschle f states that larger quantities are 

 present in germinating fatty seeds, but here some of the alde- 

 hyde may represent a stage in the conversion of fat into 

 sugar previous to the respiration of the sugar. 



Thomas % found that in the respiration of apples informal 

 aerobic conditions, neither alcohol nor acetaldehyde accumu- 

 lated, but in the absence of oxygen the respiration is of the 

 zymasic type, and both ethyl alcohol and acetaldehyde are 

 formed and accumulate ; even if much oxygen be present in 

 artificial mixtures of oxygen and carbon dioxide, the zymasic 

 form of respiration may occur owing to the increased amount 

 of the latter gas. In a mixture containing 10 to 20 per cent, of 

 carbon dioxide, the results are irregular, but when the amount 

 of carbon dioxide exceeds 50 per cent., the zymasic type of 

 respiration begins, and in such a mixture the ratio ethyl al- 

 cohol/acetaldehyde = 2. This is called, by Thomas, carbon 

 dioxide zymasis. In anaerobic zymasis, i.e. complete absence 

 of oxygen, the ratio is 50. 



Karlsen § studied the problem by ascertaining the effect 

 of ether, benzene and alcohol on the aerobic respiration of 

 wheat seedlings. He found they yielded results similar to 

 those obtaining in anaerobic conditions, and concluded that 

 the fundamental processes in aerobic and anaerobic respiration 

 are essentially the same. 



The amount of alcohol and carbon dioxide produced is a 



variable quantity depending on the amount of carbohydrate 



* Klein and Pirschle : " Biochem. Zeit.," 1926, 168, 340. 



f Pirschle : id., 1926, 169, 482. 



I Thomas : " Biochem. Journ.," 1925, >9» 927- 



§ Karlsen : " Amer. Journ. Bot.," 1925. 12, 619. 



VOL. II. — II 



