THE HISTORICAL DEVELOPMENT OF NEUROPHYSIOLOGY 



31 



movements of the limbs is an oljservation that goes 

 back at least to Descartes' posthumous treatise (171), 

 but that the act of volition in itself could also be 'felt' 

 was an idea espoused by some, including, rather sur- 

 prisingly, von Helmholtz." But a peripheral rather 

 than a central mechanism had more adherents for, 

 like Bichat, they thought that muscles must be sensi- 

 tive. 



Infiltrating the early work on spinal cord physi- 

 ology is the gradual development of the idea of the 

 reflex. The eventual emergence of a concept of reflex 

 activity grew out of centuries of attempts to explain 

 animal movements, motion receiving more attention 

 than sensation for it was considered to be the sign of 

 life. Galen had regarded movements as three in kind : 

 natural (such as the pulse), governed by the heart; 

 voluntary, governed by the soul (located in the brain); 

 and unconscious movements of voluntary muscles 

 (such as in respiration). Involuntary muscle was un- 

 known even in the days of Fernel (i 72) and Descartes 

 (i 73), both of whom emphasized a distinction between 

 movements dictated by reason and those due to the 

 appetites. The ideas of Fernel and of Descartes have 

 both long been regarded as forerunners of the concept 

 of reflex activity. The claims for Fernel rest on his 

 observation of automatic movements, some of which 

 we now know to be reflexly initiated; but the pe- 

 ripheral origin or the stimulus that caused them was 

 not recognized by him. An ardent supporter of 

 Descartes as the originator was du Bois-Reymond 

 (174) who stressed this claim in his eulogy of Miiller, 

 written at the time of the latter's death. 



The first suggestion that perhaps the spinal cord 

 could be a center for communication between nerves 

 was made by Thomas Willis (i 75) who came very 

 close to picturing the reflex. He thought that all 

 voluntary movements came from the cerebrum, all 

 involuntary from the cerebellum and that they were 

 ruled by a soul that resided both in the blood and in 

 the nervous fluid. For Willis the medulla was an 

 appendix of the brain which he likened to a musical 

 organ (30) taking air into its bellows (i.e. animal 

 spirits from the brain) in order to blow them out into 



171. Descartes, R. Traite de I' Homme, first French ed. 1664, 

 chapt. 77. 



172. Fernel, J. De Naiurali Parte Medicinae (ist ed.). Paris: 

 Simon de Colines, 1542; 2nd ed. Physiologia. 1554. 



173. Descartes, R. Traite de I' Homme, first French cd. 1664. 



174. DU Bois-Reymond, E. Gedachnissrede auf Johannes Miiller. 

 Berlin, 1858; reprinted in Reden, vol. 2. Leipzig: Veit, 

 1887. 



175. Willis, Thomas (i 621 -1675). De Anima Brutorum {De 

 Scientia seu Cognitione brutorum^. London: Davis, 1672. 



the appropriate organ pipes (the nerves). Elsewhere 

 (176) Willis showed his interest in the organ as a 

 musical instrument and gave some description of it. 



Where Willis came close to describing reflex action 

 was in stating that sen.se impres.sions carried by the 

 animal spirits to the sensorium commune (which he 

 put in the corpus striatum) went on to higher levels 

 of the cerebrum where they were perceived and 

 formed into memories. Some, however, were reflected 

 back towards the muscles ('species alia reflexa'). Al- 

 though the resultant movement was automatic and 

 although one might be unaware of the sensory stimu- 

 lus, Willis held that one was conscious of the resultant 

 muscular effect. The example he gives is irritation of 

 the stomach causing vomiting, and it is noticeable 

 that Willis's discussion of 'reflexes' comes in his chap- 

 ter on knowledge and recognition. 



Willis used 'motus reflexus' and the verb refluere' 

 in making this proposition and the terms were used 

 again by Baglivi (i 77) who refers to him. Their usage 

 of 'reflexus' reads as though it were closer to the 

 modern term than Descartes' 'esprits reflechis'.'* 

 Across the centuries the changing nuances of word 

 meanings make it impossible to catch the exact conno- 

 tation intended by an author, but Descartes' interest 

 in the reflection of light rays suggests that this may 

 have been the analogy he had in mind. 



A mechanism for the mediation of involuntary 

 movements was not the only one for which physiolo- 

 gists were .searching. The early workers were much 

 exercised by what they termed 'the sympathy of parts' 

 for they recognized an integration of body mecha- 

 nisms that eluded nervous influence flowing only from 

 the brain. Some suggested an interaction taking place 

 peripherally in a plexus, an anastomosis of the 

 sensory and motor nerve endings. Winslow (178), 



176. Ibid., chapt. 6. 



177. B.'\GLivi, Giorgio (1668-1707). De fibra moirue. 1700, 

 book I, chapt. 5. 



178. Winslow, James Benignus (1669-1760). Exposition 

 anatomique de la structure du corps humain. Paris: Duprez 

 and Desessartz, 1732, pt. VI (illustrated by plates from 

 Bartolomeo Eustachius (i 520-1 574). Tabulae anatomicae. 

 Rome: Gonzaga, 171 4); English translation by G. Doug- 

 las. Edinburgh: Donaldson & Elliot, 1772. 2 vol. 



" In discussing the sensation of outward movement of an 

 eyeball the external rectus of which is paralyzed, he says, "We 

 feel, then what impulse of the will, and how strong a one, we 

 apply to turn the eye to a given position." von Helmholtz, 

 H. Handbuch der physiologischen Optik. Leipzig: Voss, 1867, 

 parts translated into English by William James in his Principles 

 of Psychology. 



" Descartes used this term only once, in Passions de I'Ame. 



