ON NERVOUS ENERGY 67 



Climate also has a very powerful effect upon the nervous 

 system. A cold, dry climate is very favourable to the 

 production of nervous energy, but it tends to be expended 

 through the medium of physical exertion in the main- 

 tenance of heat. A cold, wet climate has a depressing 

 effect unfavourable to nervous energy, and much of the 

 bodily energy appears to be expended in maintaining 

 heat. A hot, moist climate is very unfavourable to 

 nervous energy. The climate of the West Coast of Africa 

 leaves the average European as limp as a wet rag. 

 Curiously enough, the climate of this region seems to leave 

 the native black races comparatively unaffected. Perhaps 

 this is due to the fact that their energy is mainly muscular. 

 The climate of the United States is an example of one 

 that is very favourable to the development of nervous 

 energy. The children of stolid European peasants born 

 and reared in the United States develop all the nervous 

 activity of the children of native Americans. This is 

 largely due, no doubt, to the bright dry air, as well as 

 to a diet rich in proteids. A mild, dry, bracing climate 

 is the one above all others which favours nervous energy. 

 The effect is both direct, in its stimulating effect upon 

 the nervous system, and indirect, through its influence 

 upon the social habits of the people. 



There is an optimum point for moisture and tem- 

 perature as for all other environmental factors. Ellsworth 

 Huntingdon, in his Civilisation and Climate, mentions 

 that the data for New England show that extreme dryness 

 does more harm than extreme humidity. Another point 

 which he brings out is that the optimum point is not 

 constant, but shifts continually. The optimum point of 

 to-day is not the optimum point of to-morrow. A change 

 of temperature is as beneficial as a change of air. 



As nervous energy is a product of the nervous system, it 



