INTRODUCTION 



13 



The Microscope. — Prior to the time of Harvey zoologists could 

 concern themselves almost exclusively with objects of some size. Minute 

 dissections were attempted, but were attended with difficulty and the 

 results were uncertain, because there were no good microscopes. Of 

 things that every freshman in a college class in biologj^ may see a thou- 

 sand times in a semester, the zoologists of early times were wholly 

 ignorant. Simple lenses existed from no one knows how early a period, 



Fig. 4. 



-An eighteenth century microscope. (Courtesy of American Museum of Natural 



History.) 



and their value was understood. But in those days of the lack of spe- 

 cialization, there were no great designers and manufacturers of optical 

 goods. Microscopes were planned and built by the scholars who needed 

 them. An investigator could easily spend ten times as much energy in 

 making and fitting his lenses, as in making observations with them once 

 they were completed. Under these circumstances, it is no wonder the 

 development of the microscope was slow. One of the products of this 

 amateur manufacture of microscopes is illustrated in Fig. 4. 



