144 PLANT RESPIRATION 



Chudiakow^ claim the contrary while A. Mayer,- D. Iwanow- 

 ski,^ and H. Buchner and Rapp^ have shown that in either the 

 presence or absence of oxygen, equal amounts of sugar are 

 destroyed by the fermentation process and almost equal 

 quantities of COo escape. On the strength of these results 

 Iwanowski and H. Buchner claim that yeast obtains the 

 energy necessary for its life only from the process of alcoholic 

 fermentation, in the presence of oxygen just as in its absence. 

 However, Iwanowski has already shown that living yeast 

 cells absorb small amounts of oxygen. This shows that they 

 are able to bring about oxidation processes. Kostychev and 

 Eliasberg^ have recently pointed out that in the presence of 

 oxygen, yeast develops a strong, normal respiration which pro- 

 duces for it considerably more energy than the whole process of 

 fermentation, the impetuous course of which is so striking. 

 That is to say, it is to be taken into consideration that the use 

 of one molecule of sugar in respiration furnishes just as much 

 energy as the fermentation of twenty-five molecules. The 

 amount of sugar consumed by respiration may be ascertained 

 in the following manner. First Giltay and Aberson^ and then 

 H. Buchner and Rapp^ showed by direct analyses that in the 

 presence of oxygen the ratio CO2 : C.2H5OH of yeast fermentation 

 is larger than in the absence of oxygen. Only in the latter case 

 do the quantities of CO2 and alcohol correspond to the theoreti- 

 cal equation for alcoholic fermentation. Hence we are justi- 

 fied in assuming that, with an unrestricted entry of oxygen, the 

 amount of CO-, equivalent to the alcohol is to be regarded as 

 the carbon dioxide of fermentation, while the surplus CO2 is to 

 be considered as the CO2 of respiration. On this basis it is 

 possible to calculate the amounts of sugar fermented and respired. 

 The calculations of Kostychev and EHasberg showed that about 



' Hoppe-Seyler. Uber Einwirkung des Sauerstoffs auf Garungen. 1881 ; Pedersen. 

 Medd. fri Carlsberg lab. i : 78. 1878; Hansen. Ibid. 2: 133. 1879; Chudiakow, N. 

 Landwirtschaftl. Jahrb. 23: 39i- 1894. 



•■! Mayer, A. Ber. d. chem. Ges. 13 : 1 163. 1880; Landwirtschaftl. Versuchs-Stationen 



25: 301. 1880. 



3 Iwanowski, D. Untersuch. iiber alkoholische Garung. 1894- Russian. 



* Buchner, H. und R. Rapp. Z. f. Biol. 37: 82. 1899; "Zymasegarung." 1903. 



i Kostytschew, S. und P. EUasberg. Z. f. physiol. Chem. m: 141- 1920. 



6 Giltay und Aberson. Jahrb. f. wiss. Bot. 26: 543- 1894- 



' Buchner, H. und Rapp. loc. cit. 



