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 ina 
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 sh. 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. ‘‘ Allor 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 many 
letters.” ‘‘ The French Acad- 
Fic. 20a. — Leeuwenhoek's 
Mechanism for Examining the 
Circulation of the Blood. 
