FUNDAMENTALS OF 

 CYTOLOGY 



CHAPTER I 

 THE POSITION OF CYTOLOGY IN BIOLOGICAL SCIENCE 



Man has been led by his native curiosity and his desire to understand 

 the world in which he lives to examine ever smaller natural objects. 

 Rocks, animals, plants, and even the stars themselves he has regarded 

 first as wholes, then as organizations of visible parts, later as systems of 

 invisible molecules and atoms, and eventually as vast arrays of subatomic 

 units. In the earlier stages of his investigations, he depended solely 

 upon his unaided senses, whereas the later steps were possible only after 

 he had devised special instruments, such as the microscope, telescope, 

 spectroscope, chemical balance, vacuum tube, and cyclotron. With 

 these powerful aids, he has been able to extend his observations into the 

 realms of the infinitely remote and the infinitely small; and despite the 

 indirectness of approach involved, they have led him to knowledge of 

 the utmost significance. 



Biology. — Animals and plants must have engaged primiti\'e man's 

 attention from his earliest days. In his struggle to keep alive, he was 

 inevitably led to the discovery that certain constituent parts of these 

 organisms would serve him well as food, clothing, and fibers. Even 

 his superstitions may have contributed something to his knowledge, for 

 in practicing the art of divination he could scarcely have failed to observe 

 much in the anatom}^ of animals that was new to him. 



A more scientific interest in the constitution of organisms had become 

 well developed in Greece by the fourth century B.C., when Aristotle and 

 Theophrastus produced, respectively, their famous treatises on animals 

 and plants. One can well imagine the wish of these men for keener 

 vision. In Aristotle's work on the generation of animals it is all too 

 evident that without more trustworthy information regarding minute 

 structures further speculation could hardly lead him nearer to a true 

 solution of the fundamental biological problems that held his interest. 



It was not until many centuries later that the small tissue elements 

 lying beyond the reach of unaided vision could be investigated. vSimple 



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