CHAPTER XXV 

 ANAEROBIC RESPIRATION AND FERMENTATION 



Allay the ferment prevailing in America by removing the ob- 

 noxious cause. 



— Wm. Pitt (the elder). 



In the previous chapter, respiration has been discussed as a 

 phase of oxidation, but heat and energy can be obtained in other 

 ways aside from oxidizing processes. For example, formic acid 

 was shown by Berthelot (1864) to break down into carbon dioxide 

 and hydrogen with the liberation of heat in the presence of plati- 

 num black as a catalyzer: 



HCOOH > C0 2 +H 2 +heat. 



Meyer (1871) showed that yeast could get along without free 

 oxygen, and Pfluger (1875) demonstrated that even frogs could 

 get along for a short time and continue to give off carbon dioxide 

 in an atmosphere devoid of oxygen. In this case, the output of 

 carbon dioxide is only one-third to two-thirds of the normal out- 

 put, but seedlings of Vicia faba will exhale for hours nearly as 

 much carbon dioxide in an atmosphere of pure hydrogen or nitro- 

 gen as in an atmosphere of normal air. 



Aerobes and Anaerobes.— Some of the bacteria, for example 

 the tetanus bacillus, cannot live in an atmosphere where free 

 oxygen is present. Such forms are called anaerobes as opposed to 

 normal aerobes which require free oxygen. The tetanus bacillus, 

 which cannot live in the presence of oxygen, is an obligate anaerobe,, 

 while plants like Vicia faba, which may get along for a short time 

 in the absence of oxygen, are facultative anaerobes. When placed 

 under anaerobic conditions, a normal aerobe stops growing and 

 tends to produce abnormal decomposition products. Seldom, if 

 ever, do anaerobic forms break their food down to carbon dioxide 

 and water; and, for this reason, the respiration is not so efficient 

 as in aerobic respiration, and the total amount of by-products is 

 greater. 



That plants are able to respire anaerobically and derive energy 



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