INTRODUCTION 



PHYSICAL MODELS AND LIVING ORGANISMSi 



Niels Bohr 

 Copenhagen, Denmark 



The discussion of the position of living organisms in a general 

 description of physical phe'nomena has, in the development of science, 

 passed through a number of stages. In Antiquity, the obvious diffi- 

 culties inherent in a comparison between organisms and primitive 

 machinery deeply influenced the attitude towards mechanical prob- 

 lems and even led to the attribution of vital characteristics to all 

 matter. With the abandonment of these views, at the time of the 

 Renaissance, through the clarification of the principles of classical 

 mechanics, the problem entered into another stage, stimulated by the 

 great anatomical and physiological discoveries at that period. 



Recent advances in technology, and especially the development of 

 automatic control of industrial plants and calculation devices, have 

 given rise to a renewed discussion of the extent to which it is possi- 

 ble to construct mechanical and electrical models with properties 

 resembling the behavior of living organisms. Indeed, it may be feasi- 

 ble to design models reacting in any prescribed manner, including 

 their own reproduction, provided that they have access to the neces- 

 sary materials and energy sources. Still, quite apart from the sug- 

 gestive value of such comparisons, we must realize that, in the study 

 of models of given structure and functions, we are very far from 

 the situation in which we find ourselves in the investigation of living 

 organisms, where our task is gradually to unravel their constitution 

 and potentialities. 



As regards this problem it is essential to realize from the very be- 

 ginning that in organic life we are dealing with further resources 

 of nature than in the construction of machines. Indeed, for this 



> Except for a few small additions the substance of these remarks was presented 

 in a contribution to the symposium on Models in Biology, Bristol, 1959. 



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