Bell's first claim to fame rests on his contributions to physiological psychology, of which the law bearing his name is the cornerstone. Throughout his published work he has much to say about the mind, and especially in his two favourite books, The Hand and The Anatomy and Philosophy of Expression as Connected with the Fine Arts, which testify to his capacity for shrewd observation. He delved into the art of antiquity, examined theories of the beauty of the human form, and critically studied the laws governing the expression of feeling, emotion, and passion in the movements of face and figure.
For nearly 2,000 years no one had seriously ventured to question Galen's conception of brain and nerves. Many anatomists, it is true, had suspected that the nerve fibres serving sensation and movement, though joined in the same sheath, might be distinct, and Thomas Willis (1621–75) had stated that some nerves were exclusively sensory and others exclusively motor. But, as Bell says in his preface to The Nervous System of the Human Body (1830), 'the (ancient) hypothesis that a nervous fluid was derived from the brain, and transmitted by nervous tubes, was deemed consistent with anatomical demonstration'. Furthermore, his contemporaries took it for granted that one and the same nerve fibre could serve the twofold function of conducting sensory messages and of transmitting the 'mandate of the will'.
Why, Bell asked himself, should sensation remain entire in a limb when all voluntary power over the action of the muscle is lost? And why should muscular power remain when feeling is gone? In seeking to answer these questions, he demonstrated the separate functions of the anterior and posterior roots of the spinal nerves. Some time between 1812 and 1821, his surgical and clinical 'experiments' led him to believe that movement is served by the anterior or ventral, and sensation by the posterior or dorsal, roots of the spinal nerves (Bell–Magendie law); the respective fibres are distinct but bound within the same trunks, and terminate separately, both centrally and peripherally.
From this discovery, Bell moved to the suggestion that sensory and motor functions might be served by different parts of the brain. He recognized (before Johannes Müller) the specificity of sensory nerves, identified (before C. S. Sherrington) the muscle sense, and understood the facts of reciprocal innervation (relaxation of extensor muscle while the flexor contracts). No one before him had acquired such an understanding of the human hand, and of the manner in which it reveals its superiority over the homologous organs of other animals. By dwelling on the delicate musculature of the fingers, and on the sensibility of the skin, he came to see the hand as the special organ of the sense of touch, while in the 'muscular sense' he detected a sixth sense which we now recognize as that which serves our powers of haptic perception. He saw the function of the hand as adapted to the arm and shoulder. In studying their comparative anatomy, he drew striking comparisons with the shoulder of the horse, elephant, and camel, and with corresponding organs of the mole, the bat, the anteater, and other species, including many now extinct.
Bell felt that he was continuing in the tradition of what he called 'the English School of Physiology', in contrast to the French School, which represented life as 'the mere physical result of certain combinations and actions of parts by them termed Organization'. This was an oblique reference to the Cartesian conception of 'animal as machine' (see Descartes, René), which culminated in La Mettrie's L'Homme machine.
A simple principle governed his work, namely 'that design and benevolence were everywhere visible in the natural world'. The 'different affections of the nerves of the outward senses' were, for him, 'the signals which the Author of nature has willed to be the means by which correspondence is held with the realities'. Perfect symmetry of form and function, continuous renewal of the 'material particles', and the integrity of the body amidst the ceaseless changes to which it is subject convinced him of the existence of a 'principle of life' which governed bodily structure and change.
Charles Bell must be counted among the leading men of science of the 19th century, and the most versatile of that illustrious group of men who raised Scottish medicine to pre-eminence. He combined a surgeon's intimacy with the human body with a profound understanding of its anatomy and physiology. To all this he brought considerable gifts as a writer and as a consummate medical artist.
(Published 1987)
— J. Cohen
- Bibliography
- Boring, E. G. (1926). A History of Experimental Psychology.
- Carmichael, L. (1926). 'Sir Charles Bell: a contribution to the history of physiological psychology'. Psychological Review, 33.
- Cole, F. J. (1955). 'Bell's law'. Notes of the Royal Society of London, 11.
- Cranefield, P. (1974). The Way In and the Way Out.
- Gordon-Taylor, G., and Walls, E. W. (1958). Sir Charles Bell: His Life and Times.
- Le Fanu, W. R. (1961). 'Charles Bell and William Cheselden'. Medical History, 5.
