122 SCIENCE PROGRESS 



absolutely dependent upon a supply of uncombined oxygen it 

 is the nerve tissue, yet Winterstein's conclusion is that "a 

 supply of free oxygen to the nervous system of the frog cannot 

 be demonstrated " {I.e.). 



The researches of J. Loeb tended in the same direction. 

 Concerning mammals and birds, Loeb states: "The blood 

 supply to the nerves is either lacking or is so meagre that 

 we must conclude that the functions of the nerves require very 

 little oxygen." : 



On the other hand of the three main modes of animal nutri- 

 tion, it is the deprivation of air or oxygen which brings death 

 most swiftly. Unconsciousness comes more quickly still. 

 Speck has shown that if the partial pressure of oxygen in 

 the air is lowered to below one-third of its normal value, the 

 fundament of mental activity, viz. the memory, is almost 

 instantly interfered with and total loss of consciousness rapidly 

 follows. 2 What then is the explanation ? 



A multitude of experiments have shown that many of the 

 normal products of " metabolic activity," that is of the cellular 

 chemism, are very poisonous, often to an extreme degree. 

 Further that all true proteins, whether of bacterial, vegetable 

 or animal origin, contain a highly toxic group. 3 The character- 

 istic of these highly poisonous bodies is that they are in a 

 reduced state 4 and apparently, in proportion as they are 

 saturated with oxygen their toxicity is lost. This seems 

 generally true of the poisons. To cite a familiar example, 

 carbon monoxide is deadly in almost minimal quantities, whilst 

 carbon dioxide may be supported in relatively large amounts — 

 for example, ten times that normally present in the atmosphere 

 affects the human organism but little. 



It has further been shown that it is especially the products 

 of anaerobic activity, i.e. the unsaturated vital products, which 

 are notably toxic and that this toxicity is diminished or lost 

 in the case of various bacteria when they are cultivated under 

 the influence of light in the presence of oxygen or simply 



1 Dynamics of Living Matter, p. 18, 1906. 



2 Cited after Loeb, I.e. p. 6. 



3 Cf. the interesting researches of S. M. Wheeler, Jour, of Biol. Chem. 514, 

 6, 1909, with further ref. 



4 Cf. the researches of L. Liebermann, jun., Cent. f. Bakt. I, Bd. 51, Heft 4, 

 September 1909, which go to show that all bacteria are strongly reducing 

 substances. 



