386 



FOUNDATIONS OF BIOLOGY 



heart again, and thus to supply the background for a 

 proper understanding of the dynamics of the organism as a 

 whole. With the work of Vesalius and Harvey, biologists had 

 again laid hold of the great scientific tools observation, 



FIG. 198. William Harvey. 



experiment, and induction which since then have not 

 slipped from their grasp. 



C. THE MICROSCOPISTS 



Even while the marshalling of accurate descriptions of 

 plants and animals was getting under way, and the study of 

 macroscopic anatomy and physiology was making rapid 

 strides forward, an event occurred which was destined to 

 make possible modern biology. This was an adaptation of 

 the principle of the spectacles the invention, probably by 

 Roger Bacon, of the simple microscope. Then came the 



