14 PRINCIPLES OF ANIMAL BIOLOGY 



Among the early designers and users of microscopes are to be men- 

 tioned Hooke and Grew of England, Malpighi of Italy, and Swammcrdam 

 and Leeuwenhock of Holland, all of whom flourished in the latter half 

 of the seventeenth or early eighteenth century. Hooke was too versatile 

 to be remembered much in zoology, except in connection with the develop- 

 ment of the microscope and the incidental discovery of cells in cork. 

 Grew did some good work in the anatomy of plants. The remaining 

 three microseopists just named were much more productive in the strictly 

 biological field. 



Mali:)ighi (Fig. 5) is famous for a treatise on the minute structure 

 of the silkworm; for the discover}^ of the layer of cells at the base of the 



Fig. 5. — Marcello Malpighi, 1G28-1604. (From Garrison's History of Medicine, after the 



painting by Tahor, Royal Society.) 



epidermis, which bears his name; for observations on the anatomy of 

 plants; and for work in embryology. Swammerdam is known for his 

 minute dissections of insects, snails, and clams. Leeuwenhock (Fig. 6) 

 studied blood capillaries, and the structure of muscles, and he saw and 

 figured spermatozoa (the male germ cells) without at first knowing what 

 they were. 



Although the microscopes of the seventeenth century were not power- 

 ful, compared with microscopes of today, they opened up a large field 

 for new discovery. Minute anatomy had its rise with the rise of the 

 microscopd. It is not important to name the many investigators who, 

 with the aid of these instruments, studied the systems of minute organs 



