CHAPTER II 

 THE CELL; THE COLLOIDAL CONDITION 



Who hath despised the day of little things? 



— Zechariah 4:10. 



Robert Hooke. — As a house is made up of units of concrete 

 blocks, stones, or bricks and the various parts are connected by- 

 electric wires, plumbing conduits, gas pipes, water pipes, and 

 other fixtures, so in a similar manner are plants composed of units 

 differing in structure and function. These units are called cells. 

 The discovery of the cell is generally attributed to Robert Hooke 

 (1636-1703), an Englishman, who was at the same time a pro- 

 fessor of geometry, an architect, an experimenter with flying 

 machines, and a worker in optics. He improved the compound 

 microscope which had been invented about 1590 by Zacharias 

 Jansen of Middleburg, Holland, and looked at many objects with 

 this new improved instrument. Among other things, he examined 

 a piece of cork fron the outer bark of a tree, and was much im-. 

 pressed by the fact that it was composed of many cavities sepa- 

 rated by walls, giving the appearance of a honeycomb. He says, 

 in describing his observations (1660-1665): 



I took a good clear piece of Cork, and with a Pen-knife sharpen'd as 

 keen as a Razor, I cut a piece of it off, and thereby left the surface of it 

 exceeding smooth, then examining it very diligently with a Microscope, 

 me thought I could perceive it to appear a little porous; but I could not 

 so plainly distinguish them, as to be sure that they were pores, much less 

 what Figure they were of; But judging from the lightness and yielding 

 quality of the Cork, that certainly the texture could not be so curious, 

 but that possibly, if I could use some further diligence, I might find it 

 to be discernible with a Microscope, I with the same sharp Pen-knife, cut 

 off from the former smooth surface an exceeding thin piece of it, and plac- 

 ing it on a black object Plate, because it was it self a white body, and 

 casting the light on it with a deep plano-convex Glass, I could exceeding 

 plainly perceive it to be all perforated and porous, much like a Honey- 

 comb, but that the pores of it were not regular; yet it was not unlike a 

 Honey-comb in these particulars. 



First, in that it had very little solid substance, in comparison of the 

 empty cavity that was contain' d between as does more manifestly appear 

 by the Figure. . . . 



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