CHAPTER ONE 



THE NATURE OF VIRUSES AND THEIR RELATION 



TO PHYSICS 



Introduction 



Viruses are small objects which can produce the most devas- 

 tating changes in certain living organisms. A bacterial virus 

 which invades a bacterium of over a thousand times its size 

 can in thirteen minutes have totally changed the functioning 

 of the bacterium, and instead have produced three hundred 

 replicas of itself. An animal virus, like small pox or influenza, 

 can modify the total metabolism of a whole large animal, chang- 

 ing its mean temperature drastically, and producing physio- 

 logical reactions requiring major changes in very large numbers 

 of functioning cells. 



The viruses themselves vary in size from 4,000 A diameter 

 for psittacosis to 100 A diameter for foot and mouth disease. 

 This last virus probably does not contain more than ten sepa- 

 rately recognizable molecules, yet its net results on large animals 

 are no more mild than many much larger and more complex 

 viruses. 



It is primarily because viruses possess in a remarkable degree 

 one essential feature of life — the ability to reproduce — that they 

 are exciting to study. Although a very great share of this ability 

 resides in the host organism, the fact remains that a relatively 

 simple and, in general, inert object can precipitate the formation 

 of hundreds of like objects in a matter of minutes. How does it 

 achieve this and what essential physical characteristics enable 

 it to do so ? These are the challenging questions of virus research. 



Overwhelmingly the greatest part of virus research has been 

 nonphysical in character. It has been concerned with virus-host 



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