viii ESSAYS OF A BIOLOGIST 



biological, but they are certainly ideas which must 

 present themselves to any biologist who does not 

 deliberately confine himself to the technicalities 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 Physics 

 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 

 extension 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, 

 remained in essence a quantitative change so far as 

 concerns the real life of man j 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, 



