CHAPTER V. 



The External-Body-Environment — An Analysis of it — Its Divisions into 

 Organic, Inorganic, Mental, and Physical — The Distinction between a 

 Diverse and Complex External-Environment — Summary of this and the 

 preceding Chapters. 



The External-Body-Environment. — The distinction which I have 

 drawn between the internal-cell-E and the external-body-E is 

 obvious : the one refers to the ex-corporeal material conditions 

 which operate upon the body ; the other signifies the imme- 

 diate E of each individual cell. 



It may be thought that the external-body-E is very 

 simple, but this is not so, and it is highly important to 

 understand how very varied and complex it is. The ex- 

 ternal-body-E is divided by Darwin into the inorganic and 

 the organic. The former includes, among other things, the 

 state of the atmosphere as to purity, temperature, dampness, 

 and a host of telluric conditions whereof we have little or no 

 knowledge ; also the amount of sunlight and the nature and 

 degree of muscular exercise (for when we exercise we are 

 working against the force of gravity). 



But over and above these various inorganic environments we 

 have to take into account a highly complex organic E. Every 

 organism is one of a community, and is brought into intimate 

 relation with several other organisms, which therefore stand to 

 it in the relation of external-body-E. 



Thus we may divide the external E into the organic and the 

 inorganic ; but it is necessary to make still another division 

 of this external E — viz., into the physical and the mental. This 

 division is convenient and indeed necessary, yet each in reality 

 falls under the same head, for the mental E operates through 

 the physical world. All those agencies which act upon the 

 brain and go to build up the mental world of an individual are- 



