PREFACE 



At the centre of biological science lies the concept of organization, undefined 

 but indispensable. This organization is not only one in space, as reflected in the 

 morphology of organisms, but also one in time, revealed by their behaviour. 

 There is a constant challenge to the biologist to try to understand and explain 

 these organizational aspects of biological systems in terms of simpler and 

 better-defined concepts. 



There has recently emerged in cell biology an emphasis upon the notion of 

 control mechanism, which has arisen from the very remarkable and fundamen- 

 tal insights which have been gained by molecular biologists into the detailed 

 operation of molecular control processes in cells. The possibility thus presents 

 itself that certain aspects of cell behaviour may be analysed and understood in 

 terms of the dynamic properties ofthese molecular control devices. The present 

 study is addressed to the investigation and development of this idea. 



However, in order to pursue an analysis which will carry real weight, it is 

 necessary to develop a theory which provides a quantitative foundation for the 

 study of cell organization, and does not consist simply of a quahtative des- 

 cription of cellular activities, reinterpreted in terms of control processes. This 

 requires the use of mathematical procedures, many of which will be unfamiliar 

 to the biologist. It is perhaps inevitable that this should be the case, for it can 

 hardly be expected of the biologist that he famiharize himself with all branches 

 of mathematics and physics just in the event that one of them might provide a 

 foundation for the analysis of biological phenomena. However, there is one 

 field of physical science with which all biologists do have at least a passing 

 acquaintance, and that is the thermodynamics of gases. We have all been 

 exposed to the gas laws, for example. Furthermore the notions of temperature, 

 energy, entropy, pressure, work, etc., which first arose in this field and which 

 form the cornerstones of physics, are universally famihar to scientists, and they 

 carry a strong intuitive content about the nature of the physical world and its 

 processes. 



In the present study variables analogous to these thermodynamic quan- 

 tities will be introduced for the description of the dynamic and organizational 

 properties of cells. Let it be emphasized immediately that what is involved is 

 not an application of classical thermodynamics to the study of cell behaviour. 

 My concern is rather to lay a new molecular foundation, in terms of cellular 

 control processes, for a thermodynamic-like analysis of cellular properties. 

 Physical energy, physical entropy, etc., do not actually enter directly into the 

 description of cell behaviour which is to be developed. The point of view 

 adopted is that, although appropriate for the analysis of physical processes, 

 these notions contribute very little to the understanding of biological organiza- 

 tion. However, the formal or mathematical structure of statistical physics 

 can be used for the development of essentially new notions, analogous to 



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