HISTORICAL SKETCH 423 



knowledge of the organs and tissues of which organisms are composed. 

 The cells, however, escaped observation until many centuries later, when 

 suitable lenses became available. The first compound microscope^ 

 appears to have been produced in about 1590 by Jans and Zacharias 

 Janssen, spectacle makers of Middleburg in the Dutch province of 

 Zeeland, and during the first part of the seventeenth century other 

 improved models were designed by other workers. These instruments in 

 the hands of men with scientific curiosity soon led to many significant 

 discoveries. A new world was opened to the eye of science, and the 

 compound microscope has since remained an indispensable instrument 

 in many branches of biological research. 



The first description of the cellular organization of plants w^as given in 

 1665 by Robert Hooke (1635-1703), a resident of London. Hooke's 

 interest in optics led him to examine all sorts of objects with the compound 

 microscope. In charcoal, and later in cork and other plant tissues, he 

 found small cavities like those in a honeycomb; these cavities he called 

 "cells." He had no distinct notion of the cell contents but spoke of a 

 "nourishing juice," which he inferred must pass through pores from one 

 cell to another. His many observations were embodied in his Micro- 

 graphia (1665). The chapter containing his remarks on cells is entitled, 

 "Of the schematisme or texture of cork and the cells and pores of some 

 other such frothy bodies." Quaint and crude as it now appears to us, 

 the Micrographia will always be of special interest because it was the 

 earliest work to deal wdth cells, which were to become the subject matter 

 of a new science. 



Nehemiah Grew (1641-1712), an English physician and botanist, 

 began a careful study of plant structure in 1664; in 1670 he read his first 

 important paper before the Royal Society. Further contributions 

 followed at intervals until 1682, when all of them were published under 

 the title The Anatomy of Plants. Like Malpighi, an abstract of whose 

 first work on plants was presented to the Royal Society in 1671, Grew 

 was interested in tissues and gave particular attention to the combinations 

 of these tissues in different plant organs. He was strongly impressed by 

 the manner in which the cells, which he also called "vesicles" and 

 "bladders," appeared to make up the bulk of certain tissues: " . . . the 

 parenchyma of the Barque," he said, "is much the same thing, as to its 

 conformation, which the froth of beer or eggs is, as a fluid, or a piece of 

 fine Manchet, as a fixed body." He further believed the walls of the 

 cells to be composed of numerous extremely fine fibrils; in the vessels or 

 longitudinal elements these fibrils were wound in the form of a close spiral, 

 while the vessels themselves were bound together by a transverse series 

 of interw^oven threads. He accordingly compared the structure of the 



^ For the early history of the microscope, see Disney (1928). 



