HISTORICAL DEVELOPMENT OF THE CELL DOCTRINE 131 



general facts about cells will be explained, the expansion of these 

 facts and their relation to particular fields being left for later chap- 

 ters on these topics. 



Fig. 71. — ,-1 and B. Leeuwenhoek's micro-scope (about 1673). C. Hooke's 



compound microscope (1665). 



(From Carpenter, "The Microscope and its Revelations," copyright, 1891, by J. and A. 

 Churchill, reprinted by permission.) 



Historical Development of the Cell Doctrine 



The discovery of cells was made possible by the use of the micro- 

 scope, which was invented about 1591. This instrument was first 

 used as a toy, but about 1650 it began to be utilized in scientific 



