PREFACE 



In offering this book under the present title I am aware that of many 

 possible criticisms, one might run as follows: 'Biological research is 

 a tremendous subject, continuously advancing on many fronts. How 

 can you, with five years' experience solely in a physiological laboratory, 

 write with authority about instrumentation for a field as broad as your 

 title suggests ?' 



The book might have been planned in two ways: first, the extent 

 of biological research could have been surveyed and classified. Under 

 each heading, apphcations for electronic apparatus could have been 

 discussed, then particular examples of suitable instruments taken and 

 constructional details given. Put together along these lines, the book 

 would almost certainly have been both long and repetitious. In 

 addition, a newcomer to electronics who had successfully built a piece 

 of equipment from the instructions given might neither understand 

 how it worked nor be able to modify it to extend its capabihties, or 

 even know what to do when it went wrong. 



The repetition just alluded to gives the clue to an alternative structure ; 

 that which has been adopted in fact. Electronic techniques, though 

 diverse in application, are actually rather few in number; the main 

 difference between apparatus used by workers in widely separated 

 research fields lies often less in the electronic gear proper than in the 

 transducing devices employed; that is, on the devices that link the 

 electronic circuits with the remainder of the experimental set-up. 

 Thus Worker A, interested in the movement of radioactive isotopes 

 in biological tissue, and Worker B, who wishes to count the passage 

 of action potentials along a nerve, may each employ rather similar 

 valve amplifiers and electronic counters; but A's transducer is a 

 Geiger-Miiller tube, whereas B's is an electrode system of silver wires. 



In this book, then, the spotting of applications is left largely to the 

 reader; the emphasis is upon techniques. Part I is concerned with 

 theory; beginning with the behaviour of electrical circuit elements, 

 first singly and then in groups, networks of increasing complexity are 

 considered, up to what might be called 'functional units', e.g., a stage 

 of amplification, a filter, or an oscillator. Part II is practical, and is 

 mostly concerned with electronic components, their ratings, limitations 

 and correct use. I have here to acknowledge the kindness of the follow- 

 ing manufacturers, who freely supphed samples of their products to 

 make possible the plates in this Part: Painton and Co., Ltd., for 

 Multicon connectors and high-stabihty resistors; Welwyn Electrical 



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