cytology: the study of the cell 135 



As a result of these developments, cytologists can no longer confine their 

 interests and competencies to the killing, sectioning, staining, and observing 

 of cell structures. A cytologist needs to be a geneticist as well. Whether he is 

 primarily interested in the nucleus and its chromosomes, or in the region 

 which surrounds the nucleus, the so-called cytoplasm with its inclusions, he 

 must still be something of a geneticist, for it is now known that the cyto- 

 plasm — that part of the cell which surrounds and nourishes the nucleus — 

 has also an important role to play in heredity. And he must in addition be- 

 come almost inevitably a biochemist, and preferably a biophysicist as well, 

 for many of the most intriguing problems of cytology now have to do with 

 the identification and analysis of key chemical compounds in the cell and 

 the roles which these specific compounds or classes of compounds play in 

 heredity and other cellular activities. 



Again, cytology has proved in recent years to be of marked use in the 

 solution of the problems of taxonomy and evolution. Much can be learned 

 regarding the relations between species or races by a comparative study of 

 chromosomes, with respect either to their numbers or their structures. It has 

 been discovered that evolutionary development often involves alterations 

 in chromosome number or structure, so that analysis of these cytological 

 characteristics may shed important light on evolutionary history and on 

 species relationships. 



In still another direction, cytology has proved to be of fundamental im- 

 portance, namely, in the solution of physiological problems. Physiology has 

 become increasingly concerned with something more than the functions of 

 tissues and organs, the behavior of organisms and their reactions to environ- 

 ment. When one has analyzed these activities he is still confronted with the 

 question as to the basic causes of these phenomena and is inevitably forced 

 back to the protoplasm itself — to its chemical and physical properties, to 

 the way in which the cell and its constituent parts behave, to the question 

 as to what parts of the cell initiate the processes which eventuate in physio- 

 logical activity, how these essential ingredients in the cell maintain and 

 reproduce themselves and become distributed to the daughter cells when a 

 parent cell divides. Cytology has thus found itself concerned with the most 

 fundamental questions which a biologist can ask. 



A modern cytologist, therefore, must be a man of parts — a broadly trained 

 person— ideally a biologist with chemical, physical, mathematical, and sta- 

 tistical competence. Furthermore, the type of material upon which he works 

 is likely to vary according to the problem with which he is concerned. He 

 may at one time work with bacteria, at other times with fungi, or viruses, 

 or flowering plants, or animals. Many eminent cytologists have utilized a 

 wide variety of materials, plant and animal, in the course of their experi- 

 ments. Since cytology involves all organisms equally, a cytologist should be a 

 biologist in the broadest sense if he is to be truly competent. 



