420 FURTHER EVOLUTION 



period of lack of oxygen. In Pfliiger's opinion the ability to 

 degiade carbohydrates anaerobically formed the basis of the 

 whole of the normal respiratory process. Somewhat later a 

 similar state of affairs was shown by W. Pfeffer" to exist in 

 higher plants. He showed that, in the absence of atmospheric 

 oxygen, plants can carry out so-called intramolecular respira- 

 tion which is, chemically, completely analogous with alcoholic 

 fermentation. The much more recent studies of V. Palladin** 

 and, especially, S. Kostychev^^ showed that, in the great 

 majority of cases, the process of normal respiration also 

 begins with the anaerobic degradation of carbohydrates. If 

 air is available, however, the intermediate products of alco- 

 holic fermentation are oxidised to CO2 and water by means 

 of specific oxidative mechanisms. If free oxygen is artificially 

 excluded the process will usually lead to the formation of 

 small quantities of ethyl alcohol and carbon dioxide. 



S. Kostychev*® gives the following diagram of the relation- 

 ship of the processes just referred to : 



Sugar CgHioOe 



intermediate products of fermentation 



fermentation respiration 



(2CO2 + 2C2H5OH) (6CO2 -t- 6hoO) 



A very similar mechanism was described by Pfliiger in 

 animals and was later confirmed by the profound researches 

 of O. Meyerhof," G. Embden^* and J. K. Parnas*^ who showed 

 that the tissue respiration of animals was based on an anaero- 

 bic glycolytic process completely comparable with lactic 

 fermentation. 



The primary nature of anaerobiosis is specially clearly 

 illuminated by a comparative study of the chemical nature 

 of the energy metabolism of the most diverse groups of con- 

 temporary living things. The essence of the biological concept 

 of energy metabolism is the mobilisation of the energy locked 

 up in organic compounds (of which carbohydrates are a 

 particular example) and its direction into the synthesis of the 

 components of protoplasm and into other processes necessary 

 for life. However, many obstacles lie in the way of this 



