56 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



unconditioned reflexes serving instinctual movements 

 for preservation of life led to Pavlov's ideas of cortical 

 inhibition and its relationship to sleep and hypnosis. 

 Pavlov distinguished between natural conditional 

 reflexes learned in early life and the artificially 

 conditional reflexes of the laboratory. Among the 

 first he classed the connections formed in infancy 

 between the smell or sight of food and the salivary 

 response. This observation goes back many centuries 

 and is well described by Whytt (i8i), who like Lay- 

 cock after him, recognized that the 'idea' could be as 

 powerful a stimulus as the sensory impression. 



Pavlov had in his youth been a student of Ludwig 

 and of Heidenhain; from the former he had brought 

 the insistence on a physical basis for all biological 

 processes and from the latter an interest in secretory 

 mechanisms and the phenomena of hypnosis. The 

 fertility of Pavlov's ideas and his indefatigable energy 

 drew to him an enthusiastic school of workers and b\' 

 the 1920's he had a large team working under him on 

 the many features of establishment, reinforcement, 

 extinction and inhibition of conditional reflexes. He 

 was a well-loved teacher, though a man of fiery 

 temperament. Sherrington has left a vignette of him 

 at the age of 65 describing him as "overflowing with 

 energy, although an elderly man; he was spare in 

 figure and alert and humourous in manner." Even 

 at the end of a long working day on encountering a 

 stairway he "ran up it rather than walked." Sherring- 

 ton came away from this visit, made in 191 4, with a 

 great enthusiasm for the leader of Russian neuro- 

 physiology C320). 



Pavlov's ideas of the reflex became more diffuse 

 and more nebulous as he grew older. Experiments to 

 test the modes of behavior of animals to conditioning 

 stimuli were less difficult to design than ones to test 

 the hypothesis advanced to explain them. Temporary 

 neuronal connections in the cortex proved easier to 

 postulate than to prove. Pavlov's own attempts were 

 with decorticate preparations (a technique that had 

 been u.sed before him by Sechenov) and it is only in 

 recent times that the electrophysiologist's tools have 

 been applied to this problem. 



320. Sherrington, C. S. Marginalia. In: Science, Medicine and 

 History. Essays in Honour of C. Singer, edited by E. A. Un- 

 derwood. London: Oxford, 1953. 



As the second half of the twentieth century unfolds 

 the neurophysiologist in his search for brain mech- 

 anisms continues to use the three main categories of 

 experimental procedure: anatomical, ablative and 

 electrical. It is the great advance in electrical stimula- 

 tion and recording that marks this era of investigation 

 from its predecessors, although it is only through 

 knowledge from all sources that progress can be 

 achieved in an understanding of the brain. 



Neurophysiology came into being as a specialized 

 branch of endeavor when the nervous system no 

 longer had to compete with the humors and with the 

 blood as the principal coordinator of the body. With 

 the recognition that sensation and motion were medi- 

 ated by the nerves their position became unassailable, 

 for movement was regarded as the sign of life. Slowly 

 the concept of neural organization began to be pieced 

 together and levels of integration were postulated, in 

 the spinal cord, in the cortex and in the deeper struc- 

 tures of the brain. The period of analysis of the func- 

 tion of each structural unit, of each sector of the 

 nervous system, was followed b\' a shift of emphasis 

 towards a synthetic consideration of neural activity. 

 The search began for the physiological mechanisms 

 of mental processes, of consciousness, of memory — all 

 terms and concepts that had belonged to another do- 

 main of thought. In the neurophysiolog\' of today we 

 find both angles of approach, ranging from analysis 

 of the intimate physicochemicai basis of nervous 

 structure and dynamics to the synthesis of action that 

 we call behavior of the organism. 



The writer expresses her great indebtedness to the authors 

 of many articles and books not listed in the abridged bibli- 

 ography that follows. She adds her thanks to those who have 

 sent her material in correspondence, and in particular would 

 mention appreciatively: Dr. Maria Rooseboom for the use of 

 material and microfilms from the National Museum for the 

 History of .Science at Leiden; Dr. Palle Birkelund, Director of 

 the Danish Royal Library; Dr. .\uguste Tournay for a photo- 

 stat copy of Pourfour du Petit's Letters, the Institution of Elec- 

 trical Engineers and Miss Helen G. Thompson for access to 

 material collected by Silvanus P. Thompson on Gilberd; Miss 

 Anne Caton for family photographs and material from the 

 diaries of Richard Caton; Dr. Andrei Jus of Pruszkov for photo- 

 stats of Adolf Beck's doctoral thesis; and F. Czubalski of War- 

 saw for information about Beck's works. For details of Beck's 

 life the writer expresses warm appreciation to his daughter, 

 Mme. Jadwiga Zahrzewska. 



A SHORT LIST OF SECONDARY SOURCES 



Space does not permit the listing of all the articles to whose 

 authors the writer is indebted for information. The following 

 books have been selected for the special interest they may 

 have for the physiologist. Where possible, works in the English 

 language have been chosen. 



Bence Jones, H. On Animal Electricity. London: Churchill, 1852. 

 Bettmann, O. L. .4 Pictorial History of .Medicine. Springfield: 



Thomas, 1956. 

 Boring, E. G. A History of Experimental Psychology. New \'ork: 



.\ppleton, 1 929. 



