OXIDATION AND REDUCTION 599 



Certain fine particles have been separated fi'om liver cells, which absorb oxygen 

 and give off carbon dioxide to the extent of one-fifth of that of the intact cells. 



The consumption of energy by cells for the purpose of opposing the mixing of 

 their constituents by diffusion, maintaining intact the properties, electrical or 

 otherwise, of the semipermeable membranes and so on, must be remembered 

 in the interpretation of the oxygen consumption by tissues which perform 

 no external work. 



There is some evidence that, in the cases of yeast and bacteria, energy is used 

 up for the purpose of growth. 



The reducing power of tissues depends to a large extent on their degree of 

 activity, or, in other words, of the relative rate at which oxygen is consumed and 

 supplied. The experiments of Ehrlich on the question are described briefly in 

 the text. 



When organisms emit light, it is by a process of chemi-luminescence, in which 

 the wave length of the light is much shorter than that corresponding to the 

 temperature of the source. It is an oxidative process in which the chemical energy 

 is used directly for conversion to light energy, without passing through the stage 

 of heat. The system concerned, although secreted by cells, is active apart from 

 living protoplasm. 



The nature of certain flower pigments is described in the text and their relation 

 to oxidising and reducing enzymes indicated. 



LITERATURE 



Autoxidation. 



Engler and Weissberg (1904). 



Oxidation in the Cell. 



Ehrlich (1835). Bach (1913, 1). Kastle (1910). 



Reduction Processes. 

 Bach (1911, 2). 



Influence of " Structure." 



Warburg (1913, 1, and 1914). 



Production of Light. 

 Mangold (1910). 



