The afferent nervous system from a new aspect : conclusions ... from investigations ... in conjunction with W.H.R. Rivers and J. Sherren / Henry Head, W.H.R. Rivers, J. Sherren.

  • Henry Head
Date:
1905
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Licence: In copyright

Credit: The afferent nervous system from a new aspect : conclusions ... from investigations ... in conjunction with W.H.R. Rivers and J. Sherren / Henry Head, W.H.R. Rivers, J. Sherren. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    that of the fifth hinibar root. Consequently, destruction of this nerve produces a widespread loss of sensation to prick, with an extremely well-defined border on the shin and dorsal surface of the foot. The sensory mechanism iu the peripheral nerves is thus found to consist of three systems :— (I.) Deep sensibility, capable of answering to pressure and to the movement of parts, and even capable of pro- ducing pain under the inflaence of excessive pressure, or when the joint is injured. The fibres, subserving this form of sensation, run mainly with the motor nerves, and are not destroyed by division of all the sensory nerves to the skin. (11.) Protopathic sensibility, capable of responding to painful cutaneous stimuli, and to the extremes of heat and cold. This is the great reflex system, producing a rapid widely diffused response, unaccompanied by any definite appreciation of the locality of the spot stimulated. (III.) Epicritic sensibihty, by which we gain the power of cutaneous localisation, of the discrimination of two points, and of the finer grades of temperature, called cool and warm. Let us now pass to the consideration of the arrangement of sensation in the central nervous system. The view I shall put forward is based upon the examination of a series of cases of haemorrhage into the spinal cord, and of injuries affecting its substance, producing what is usually known as Brown-Sequard paralysis. With these we have compared the sensory changes in syringomyelia and tabes dorsalis. Now, all these conditions demonstrate that, as soon as a sen- sory impulse reaches its first junction in the spinal cord, it becomes shunted into tracts devoted to the conduction of impulses, grouped in a way different from that found in the peripheral nerves. It is no longer a question of protopathic, epicritic, or deep sensibility; the tracts in the central nervous system are devoted to the conduction of impulses concerned with pain, heat, cold, and touch. Thus, in Brown-Sequard paralysis, motion is lost in the one limb, and all sense of pain, heat or cold, is abolished in the other. Careful examination of this loss of sensation shows that sensibility is equally lost to all forms of tem-
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