Influence of Environment lopon the Organism. 447 



3. History. — Our analysis of the environment must, how- 

 ever, be prefaced with a brief historical note. That external 

 surroundings influence the organism is no new nor theoretical 

 notion. Even as far back as Hippocrates there was recogni- 

 tion of the fact that climate and outside forces change the 

 body, while in common speech and everyday action the fact 

 is constantly assumed. Nor among naturalists who have 

 made special study of the factors causing change, has the 

 importance of the environment been overlooked. Those 

 before Darwin may be divided into two schools, according to 

 the degree of directness which they attributed to outside in- 

 fluence. The one school, represented by Buffon, Treviranus, 

 and Geoffrey St Hilaire, regarded the surroundings as directly 

 hammerinoj chanoes on the oroanism. The other school, 

 represented by Erasmus Darwin and Lamarck, regarded the 

 environment as only indirectly prompting to change. In 

 Darwin's works the only action of the environment which 

 can be said to be much emphasised is its indirect destructive 

 action in the struggle for existence. Post-Darwinians vary 

 in the degree to which they allow direct transforming 

 action, in addition to natural selection. Thus it is fair enough 

 to say that Spencer and Semper allow more importance to 

 direct external influence, than do naturalists so widely 

 separated as ISTageli and Weismann. To Claude Bernard we 

 owe a clear concrete treatment of physiological problems 

 from the point of view indicated in his definition of life, — 

 as a harmonious interaction between the oroanism and the 

 physico-chemical ambient conditions. 



4. Analysis of the Environment. — Those external influences, 

 which have been shown to affect living matter, may be 

 arranged in various ways. They may, for example, be dis- 

 tinguished as animate and inanimate, but the former are 

 comparatively few, and are in most cases resolvable into 

 combinations of the latter, and again some further division of 

 the large sphere of inanimate influence is imperative. Or it 

 may be proposed to distinguish the external influences as 

 either (ci) chemical, or (6) molecular. The first division would 

 include such factors as the chemical composition of the 

 medium and the character of the food ; the second set 



