Viii PREFACE 



does not deliberately confine himself to the tech- 

 nicalities of his science. 



The biologist cannot fail to be impressed by the 

 fact that his science to-day is, roughly and broadly 

 speaking, in the position which Chemistry and Phys- 

 ics occupied a century ago. It is beginning to reach 

 down from observation to experimental analysis, and 

 from experimental analysis to grasp of principle. 

 Furthermore, as the grasp of principles in physico- 

 chemical science led speedily to an immense new ex- 

 tension both of knowledge and of control, so it is not 

 to be doubted that like effects will spring from like 

 causes in biology. But whereas the extension of 

 control in physics and chemistry led to a multiplica- 

 tion of the number of things which man could do 

 and experience, the extension of control in biology 

 will inter alia mean an alteration of the modes of 

 man's experience itself. The one, that is to say, re- 

 mained in essence a quantitative change so far as 

 concerns the real life of man; the other can be a 

 qualitative change. Applied physics and chemistry 

 bring more grist to the mill; applied biology will 

 also be capable of changing the mill itself. 



The possibilities of physiological improvement, of 

 the better combination of existing psychical faculties, 

 of the education of old faculties to new heights, and 

 of the discovery of new faculties altogether — all this 

 is no Utopian silliness, but is bound to come about 

 if science continues her current progress. 



Take but one example. In the first half of last 



