44 THE DATA OP BIOLOGY. 



16. This chapter will have served its purpose if it has 

 given a conception of the extreme modifiability of organic 

 matter by surrounding agencies. Even were it possible, 

 it would be needless to describe in detail the immensely 

 varied and complicated changes which the forces from mo- 

 ment to moment acting on them, work in living bodies. 

 Dealing with biology in its general principles, it concerns us 

 only to notice how specially sensitive are the substances of 

 which organisms are built up to the varied influences that 

 act upon organisms. Their special sensitiveness has been 

 made sufficiently manifest in the several foregoing sections. 





