8o PLANT RESPIRATION 



the complete oxidation to COo and water, by atmospheric oxy- 

 gen, of the labile substances formed intramolecularly. 



This conception is the basis of all modern theories of the 

 connection of anaerobic with normal respiration. Yet it is 

 worthy of note that the facts experimentally estabHshed by 

 Pfliiger could serve just as little to confirm his theory as could 

 the balance of the alcohohc fermentation of yeast confirm 

 Lavoisier's law of the conservation of matter (as is known, 

 Lavoisier and others used the fermentation of sugar by yeast 

 as a particularly good illustration of his law). The "anaerobic 

 respiration" of animals is to all appearances analogous not to 

 alcohohc but to lactic acid fermentation. The first phase of 

 oxygen respiration in animal bodies proceeds in the absence of 

 oxygen without forming CO2. The production of CO2 observed 

 by Pfliiger is actually not a general, widespread phenomenon 

 and has nothing to do with the first phase of respiration. On 

 the other hand, Pfliiger did not know of Pasteur's investigations 

 when he published his communication, else he would have per- 

 haps withdrawn his assumption of the formation of hypothetical 

 "labile" substances, because ethyl alcohol is less labile and less 

 capable of oxidation than is the sugar from which it is produced. 

 Contrary to the assumption of Pfliiger, the oxidation of sugar 

 is not expedited through the formation of alcohol. Still 

 Pfluger's idea was most prolific, and the strange part is that he 

 was apparently correct in the main. This is a novel illustration 

 of the role of chance in scientific discoveries. 



It is evident that neither Pasteur nor Pfliiger conceived of 

 anaerobic respiration as an abnormal, pathological phenome- 

 non. Nageli,^ Brefeld,^ and Sachs^ took a different attitude. 

 In his book "Theorie der Garung" (Theory of fermentation) 

 which was so quickly discredited, Nageli expressed his opinion 

 of Pasteur's discovery of anaerobic respiration in the following 

 manner: "Here, however, it is actually an abnormal phenome- 

 non, since it is wanting in cells which are in a healthy and 

 vigorous condition and first appears whenever they are deprived 



' Nageli C. Theorie der Garung. 1879. P. 117. 



- Brefeld, O. Landwirtschaftl. Jahrb. 5: 281. 1876. 



' Sachs, J. Vorlesungen uber Pfianzenphysiologie. 1882. Pp. 486-487. 



