INTRODUCTION OF THE MICROSCOPE 



83 



arranged to examine the circulation of blood in the trans- 

 parent tail of a small fish. The fish was placed in 

 water in a slender glass tube, and the latter was held in a 

 metallic frame, to which a 

 plate (marked D) was joined, 

 carrying the magnifying 

 glass. The latter is indi- 

 cated in the circle above the 

 letter D, near the tail- fin of 

 the fish. The eye was ap- 

 plied close to this circular 

 magnifying-glass, which was 

 brought into position and 

 adjusted by means of screws. 

 In some instances, he had a 

 concave reflector with a hole 

 in the center, in which his 

 magnifying-glass was insert- 

 ed; in this form of instru- 

 ment the objects were illu- 

 mined by reflected, and not 

 by transmitted light. 



His Scientific Letters. — 

 His microscopic observations 

 were described and sent to 

 learned societies in the form 

 of letters. " All or nearly all 

 that he did in a literary way 

 was after the manner of an 

 epistle," and his written com- 

 munications were so numer- 

 ous as to justify the cogno- ' 



men, "The man of manv ^ * IG " . 20a. — Leeuwenhoek's 

 .,..__ Mechanism for Examining the 



letters." The French Acad- Circulation of the Blood. 



