in LIVING MATTER 69 



culture. These modifications consist essentially in processes of 

 oxidation, and the anaerobes appear to he incapable of utilising 

 highly oxidised proteins in their assimilation. Accordingly, they 

 can only develop when these substances are once more reduced, 

 which is effected either by artificially removing the oxygen, or 

 (after Tarozzi) by adding to the broth a scrap of fresh organ 

 aseptically prepared, which acts as a reducer, in virtue of the 

 chemical processes of which it is the seat, and favours the develop- 

 ment of the anaerobes. In this case it is not necessary to remove 

 the oxygen before the bacteria can develop. This explains how 

 such development takes place naturally when these bacteria are in 

 the presence of tissues of animals that have just died, or, generally 

 speaking, whenever they find protein matters at their disposal 

 which have not suffered profound oxidative changes. And this 

 is why all anaerobes belong exclusively to the class of putrefaction 

 microbes (saprophytes). 



According to the work of Duclaux, Gautier, and Ehrlich, 

 anaerobic metabolism may be recognised not only in a great 

 number of microbes, but in a still greater number of plant and 

 animal cells. 



Many decompositions of organic molecules due to enzyme action 

 within the cell, or in external secretions, are produced without 

 intervention of atmospheric oxygen, and are accompanied by a 

 development of energy which is partly utilised by the cells for 

 their constructions or organic syntheses. Thus, e.g., the katabolic 

 action of beer yeast, in the absence of oxygen, breaks up glucose 

 into alcohol and carbonic acid, with evolution of heat which is 

 partly employed in the multiplication of the cells of the ferment. 

 In a well-aerated medium the same beer yeast, on the contrary, 

 effects complete oxidation of the molecule of glucose, converting it 

 into water and carbonic acid, and in this case there is a greater 

 development of heat and a far larger multiplication of Saccharo- 

 ini/ces. Pasteur's interpretation of these phenomena is very 

 illuminating : Saccharomyces, in order to nourish and reproduce 

 itself, makes great use of the energy developed in the oxidation of 

 sugar, when it is in an oxygenated medium. When oxygen is 

 scarce, it utilises the inferior amount of energy which it is able 

 to develop by abstracting oxygen from the fermentable material, 

 i.e. from the same sugar, by a kind of internal oxidation. 



Accordingly, it is not oxygen as such that is essential to life, 

 but the energy that is developed by any kind of oxidation. Green 

 plants have less need of oxygen than animals, because they obtain 

 from the sun's rays a great part of the energy which they require 

 in fixing the carbon. If the majority of living beings positively 

 demand free oxygen, it is because much heat is developed in its 

 combinations, which can be utilised in a variety of ways. 



In proof of the extent to which oxygen is essential to the life 



