6 



Mechanics and Physiology of 



Cell Division 



The description of mitosis which was presented in Chapter 5 dealt 

 only with the question of what happens during more or less typical 

 mitosis. The nature of the functions performed and the manner in which 

 they are performed that enable the product of one mitosis to reach a 

 subsequent division are events that constitute a group of problems 

 the answers to which are of vital importance. A purely morphological de- 

 scription of the mitotic process does not give us very much information 

 concerning its dynamics or how it actually occurs. The dynamics of cell 

 division may well be designated as the problem of the mitotic cycle. 

 This problem introduces many questions concerning the physiological 

 factors involved and their interrelationship during the various stages of 

 the cycle. Although the question of the mitotic cycle has been investi- 

 gated for over three quarters of a century we are still without many 

 major guiding principles. It is hoped that the application of the modern 

 experimental approach and quantitative analysis will ultimately resolve 

 some of the mysteries. Because of the bearing which cell division in 

 general has on growth, both normal and abnormal, this is a very basic 

 and important problem. Consideration of general biological information 

 together with modern biochemistry and physiology allows one to pose 

 some very definite questions and to set up models which may be used in 

 experimental design. It is our purpose in this section to introduce some 

 of these questions and to indicate the type of experimentation which is 

 currently being used in an attempt to provide answers. 



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