252 SCIENCE PROGRESS 



there are still good reasons for accepting the doctrine in a 

 modified and reduced form. 



The fundamental character and universal distribution of 

 anaerobic respiration is supported by a large body of evidence, 

 much of which is described in an article published three years 

 ago in this journal by C. D. Snyder 1 on " Life without Oxygen." 

 Snyder points out that what appear to be the simplest forms of 

 life are anaerobic still, and that the majority of lower organisms, 

 both plant and animal, can live under anaerobic conditions more 

 or less continuously. He states that the fundamental chemical 

 processes of the cell in all organisms, even the highest, are 

 anaerobic, and that phenomena of oxidation are secondary, and 

 have been gradually built up in the course of evolution. Need 

 of oxygen appears to increase pari passu with increasing com- 

 plexity of chemical and morphological organisation. 



But little direct evidence is adduced by Snyder in favour of 

 the fundamentally anaerobic character of the vital process, so 

 it is desirable to discuss the hypothesis in some detail. It is 

 supported chiefly by two lines of experimental evidence. One, 

 the production of C0 2 by animals kept anaerobically, will be 

 referred to later, whilst the other concerns the existence, in 

 many organisms, of hydrolytic enzymes which in the complete 

 absence of oxygen break down food material with the liberation 

 of heat and other forms of energy. This evidence begins with 

 Buchner's 2 discovery of zymase in 1897. After mixing washed 

 yeast with sand and grinding with a heavy mortar, a juice can 

 be expressed containing numerous intracellular enzymes, the 

 most interesting of which is that responsible for the alcoholic 

 fermentation typical of living yeast cells. When mixed with 

 a solution of glucose, laevulose, or galactose, the yeast juice 

 decomposes the sugar according to the equation : 



C 6 H 12 6 = 2C 2 H 6 + 2CO* 



Disaccharides as cane-sugar and maltose, and polysaccharides 

 such as glycogen, are likewise acted on, but they are hydrolysed 

 to monosaccharides by the intracellular invertase, maltase, 

 and amylase enzymes present before being attacked by the 

 zymase. 



1 C. D. Snyder, Science Progress, 6, N.S. p. 107, 191 1 ; also 4, p. 579, 1009. 

 See also Lesser, " Leben ohne Sauerstoff,'' Ergeb. d. Physiol. 8, p. 742, 1909. 



2 Cf. Die Zymasegahrung, by E. Buchner, H. Buchner, and M. Hahn, 1903. 



