Preface 



It is probably safe to say that there is no aspect of an animal's behavior 

 which is not influenced to some extent by the activity of sense organs. 

 Although we can no longer accept the view that behavior is a simple 

 compendium of strictly reflex actions (derived from and triggered by the 

 momentary events which are presented to the peripheral nerves), there 

 can be no doubt that even those aspects which arise endogenously 

 within the central nervous system can be influenced in subtle ways by 

 the appropriate sensory inflow. The precision of the mechanisms by 

 which sensory receptors detect stimulus energy is, thus, critical to the 

 effective functioning of an animal within its environment. All organisms 

 extract energy from their environment in order to exist; sense organs 

 are unique in their ability to sample the quality and magnitude of 

 available energy sources, and to communicate this information to the 

 organism as a whole. We are now vaguely aware that the primary step 

 involves a structural change in the cell membrane, but many details of 

 the problems which have fired the imagination of physiologists for many 

 decades remain unexplained. The earliest — perhaps the most primitive 

 — aspects of the sensory process are still the ones about which we have 

 the least knowledge, and revolutionary techniques may have to be 

 developed before they can be elucidated. 



During the early years of this century methods were perfected which, 

 for the first time, made it possible to monitor the electrical activity of 

 peripheral nerves. This entirely new approach to sensory physiology 

 was soon firmly established as attention was focused by Adrian and his 

 colleagues on the intriguing questions raised by the results of psycho- 

 physical studies which had been performed during the nineteenth 

 century. An early optimism concerning the ultimate success of this 

 approach was apparently justified; there can be no doubt that the most 

 dramatic advances in the field during the last forty years have been made 

 in the understanding of the electrical events involved in stimulus 

 detection, although this trend has perhaps led to the neglect of other 

 experimental approaches. The six chapters of this book will examine 

 the results of these electrical studies in the light of what is known of the 

 structure and physical properties of the cell membrane. This is 

 admittedly a rather limited aspect of the research presently under way 

 on the perception of environmental stimuli. Sensory cells rarely occur 



