THE microscope was invented in 1590 by a Dutch spectacle-maker, one Zacharias Jansen, a resident of Middelburg. It was some threequarters of a century later, before Robert Hooke was to publish in 1665 his Micrographia embodying the results of his researches in this field. Hooke himself was originally an architect and professor of mathematics addicted to the study of optics and interested also in what was at that time the virtually insuperable problem of building a flying machine. He produced a compound microscope which, in comparison with Jansen's and the model which Leeuwenhoek was using at about the same period, was strikingly perfect.
Hooke gives a description of the structure of cork in the eighteenth section of Micrographia. Cork contains, says he, numerous cavities -- which he denominates "pores" or "cells" -- reminiscent of the structure of a honeycomb, sponge, or pumice stone.
Almost contemporaneously, Marcello Malpighi pointed out in 1675 that cell structure is observable in many plants and in certain animal organs. For all that, neither Hooke nor Malpighi arrived at the conclusion that the basic factor was actually what was contained in the cell itself and not the material by' which it was surrounded.
Around that same time, in 1673, Leeuwenhoek discovered certain free or independent cells, to which however he did not attribute any specific biological significance; these were the red blood corpuscles, spermatozoa, infusoria, yeast cells and others. Leeuwenhoek, though, was but an amateur not ranking particularly high in the opinion of his contemporaries; nevertheless his discoveries were of very real importance for the advancement of science.
These various observations remained unmentioned for more than a century because of the predilection for organistic standards in vogue at that time. The organ, both in plants and in animals, was held to be the source of all functions. At the beginning of the nineteenth century, however, Xavier Bichat in 1802 saw, in a flash of inspiration, that the