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in accordance with the Darwinian principle of 

 natural selection. This matter — the modifications 

 for good or bad wrought in our nature by the 

 influence of external conditions — embraces a wide 

 field of study and comprehends nothing less than 

 the possession of a knowledge of the varied 

 operations, with the laws determining them, going 

 on around us in order that we may understand the 

 manner in which they are brought about. It is a 

 vast subject, but the mind of man has already done 

 much, and there is reason to think will do much 

 more, towards penetrating it ; and as with the 

 amount of knowledge acquired power is possessed 

 — that is, the power of arranging conditions or 

 operations so as to render them subservient to the 

 production of a desired effect, man stands in the 

 position of an increasingly powerful agent in the 

 realm of nature. Must not the mind itself, then, 

 through which this is accomplished be reckoned as 

 a power — a great power amongst the powers of the 

 universe? In our special department as medical 

 practitioners it falls to us to apply the power which 

 knowledge gives us towards preventing unnatural 



