34 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



Afinlifsts 



of 



Tlir Iliustiillir iVu.,u.s Sj/slem. 



FIG. 22. Lffl. Marshall Hall. Right: one of his experiments 

 to demonstrate the three parts of the reflex arc. The arc was 

 broken by any of the following procedures: a) skinning the 

 extremity (at 5) (the 'esodic' nerves); A) sectioning of the 

 "brachial or the lumbar or femoral nerve leading to the point 

 irritated" (i.e. the exodic nerve' at 2); or c') removing the spinal 

 mcirrow (the spinal centre')- (From Hall, M. Synopsis of the 

 Diastalttc J^'ervous System: being outlines of the Croonian Lec- 

 tures delivered at the Royal College of Physicians in April 

 1850.) 



the idea of an inherent vis nervosa in the nerves that 

 enabled them to function in isolation from the brain 

 and he supported this argument by citintr the move- 

 ments of anencephalic monsters. In his view the 

 ■purpose' of reflex activity was preservation of the 

 individual. 



Here the history of reflex activity rested for nearly 

 30 years and the next advance was a technical rather 

 than a conceptual one. This was the perfection by 

 Legallois (187) of a method for the artificial respira- 

 tion of mainmals and from then on, in many labora- 

 tories, heads began to fall. Legallois, by sectioning the 

 neuraxis serially from above and from below, nar- 

 rowed the center of activity drastically and was so 

 impressed by the amount of sensorimotor function 

 left in a segment that he rather sweepingly concluded 

 that the spinal cord was the principal seat of sensation 

 and the source of voluntary motion. Although this 

 extreme view did not gather many adherents, it was 

 clear that the spinal cord could no longer be thought 

 of as a mere prolongation and bundling together of 

 peripheral nerves. On the contrary, the tendency now 



187. Legallois, Julien Jean Cesar (1770-1814). Experiences 

 sur la principe de la vie, notamment stir celui des mouvemenls 

 du coeur, el sur le siege de ce principe. Paris: D'Hautel, 1812. 



was to regard it as a caudal extension of the brain. 

 Legallois should be remembered for being the first to 

 recognize clearly that the respiratory center lay in the 

 medulla oljlongata. 



This was the setting of the stage for the man who 

 lifted the whole subject of reflex activity into the 

 framework of modern neurophysiology and into 

 clinical science. Marshall Hall, an Englishmen edu- 

 cated in the great school at Edinburgh where he was 

 a pupil of the third Monro, was a successful practising 

 physician who set up a laboratory in his own house 

 (in Malet Street where the present buildings of 

 London L'niversity stand). Here he worked on his 

 animals, mostly frogs and reptiles, collating his obser- 

 vations (188) with those he made on patients (189). 

 His acumen enabled him to perceive several details 

 that had escaped his predecessors. For example, the 

 writhings of the decapitated snake that had led Whytt 

 to a postulate of lingering 'life' within the cord were 

 recognized by Hall as motor responses to the renewed 

 sensory stimuli set up by each movement 



Like Unzer, Hall in his work on the machine-like 

 movements of decapitated animals protected himself 

 from onslaught by stating them to be "all beautiful 

 and demonstrative of the wisdom of Him who fashion- 

 eth all things after his own Will." Hall, again like 

 LTnzer, realized that the sensory impression that set 

 ofl' a reflex need not be consciously perceived, al- 

 though he was consistently remiss in acknowledging 

 the contributions of his predecessors. He also ignored 

 the work of his contemporaries, for nowhere does he 

 refer to the great blossoming of knowledge of nerve 

 physiology that was taking place at this time and 

 which has been reviewed in an earlier section of this 

 essay. He seems also to have ijeen unaware of the con- 

 tractility of involuntary muscle although Baglivi 

 (190) over a hundred years before he had made the 

 distinction between smooth and striated muscle. Hall 

 had many detractors who vigorously accused him of 

 plagiarism, both from Miiller and from Prochaska. 

 The first challenge was easier to meet than the second, 

 for Hall's earliest communication (191) antedated 

 Miiller's publication (94) on decapitated animals by 

 one year. In the published report of this first paper, 



188. Hall, Marshall (1790-1857). .\'ew Memoir on the Nerv- 

 ous System. London, 1843. 



189. Hall, M. Diseases and Derangements of the Nervous System. 

 London: Bailliere, 1 841. 



190. Baglivi, Giorgio (1668-1707). Opera omnia medico- 

 praclica et anatomica. Leyden: Anisson & Posuel, 1704. 



191. Hall, M. On a particular function of the nervous system. 

 Proc. Z^ol- •^O'^- part 2, p. 189, Nov. 27, 1832. 



