8 Faraday, Biological Aspect of Cancer. 



the growth first appeared. Here then we have healthy 

 cells becoming malignant, in the first place through some 

 condition of the environment. Then one of the converted 

 cells escapes, travels, and sets up a parasitic colony 

 elsewhere. Such a travelling cell is, to all intents and 

 purposes, a pathogenic micrococcus evolved from originally 

 healthy cells. Let us recapitulate. We begin with a 

 healthy epithelial tissue, the cells of which are capable of 

 differentiation to fulfil the various co-operative functions 

 required. Owing to some change in the environment, or 

 say the food supply for the renewal of the tissues, they 

 lose their differentiation power and revert to, or remain at, 

 what 1 may describe as the simplest cryptogamic or 

 thallophyte stage of their life-history. Under the changed 

 condition their vital activity developes itself in purely 

 algaceous or fungoid growth, and for the same reason, and 

 under the influence of increasingly abnormal conditions, 

 they eventually develope a parasitic power. A cell then 

 escapes and, as a pathogenic micrococcus, sets up, under 

 the same favouring conditions, similarly parasitic colonies 

 elsewhere. Is not such an assumed development of 

 morbid virulence analagous to the variation from the 

 " vaccine " to the deadly contagium vivuin ? 



But we have now to ask ourselves why this arrest of 

 development at what may be called the mere cryptogamic 

 stage, and why this development of vigorous parasitism ? 

 In endeavouring to answer these questions we must first 

 recognize the fact as demonstrated, that changes in the 

 chemical and physical environment have an extraordinary 

 influence on the lower forms of life. It has been abun- 

 dantly demonstrated that the cultivation of microbia in 

 the absence of free oxygen and sunlight developes 

 parasitic vigour in an extraordinary way, and that free 

 oxygen and sunlight are inimical to parasitic vigour. 



