Pain / by Thomas Lewis.

  • Lewis, Thomas, Sir, 1881-1945.
Date:
1942
Catalogue details

Licence: In copyright

Credit: Pain / by Thomas Lewis. Source: Wellcome Collection.

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    positional sense. Thus, a coil of bowel giving rise by its con¬ traction to pain in the midline of the body can hardly be ex¬ pected ever to do otherwise even if it lies, as Mackenzie observed it, twelve inches from the midline. The viscera are organs of which we are normally almost completely unconscious, and none of them is endowed with sense of position. Full realisation of these facts makes it seem less remarkable that, while pain aris¬ ing in the viscera is referred to somatic structures belonging to the same segment, pain arising from the somatic structures is not referred to the region of the viscus. Yet there would be no apparent reason why the latter form of reference should not occur if reference were merely dependent upon extension of a commotion from one area of grey matter to the next. This hypothesis of spread within the cord is also difficult to accept, in view of there being no segmental spread when skin is stimu¬ lated. However strongly a point of skin is stimulated, pain aris¬ ing from it diffuses very little; and, if it seems to diffuse, it does so radially and equally. Why do not pain impulses derived from skin set up this supposed commotion in the cord? The answer seems to be that the commotion is hypothetical and not real and that reference is a phenomenon which goes hand in hand with inability to localise. Segmental reference is a phenomenon of the deep pain system and is not found in the cutaneous pain system. The unusually wide reference of very severe pain derived from deep structures is probably purely a central phenomenon. In dealing with referred segmental pain, I have deliberately divorced it from the question of referred tenderness for reasons that will appear. Segmental 'pain and superficial anaesthesia.—Weiss and Davies (239) reported that they were able to abolish pain of visceral origin by anaesthetising the skin in the region to which pain is re¬ ferred. The idea here is that the pain is due to normal impulses ascending from the skin to play on an “irritable focus” in the spinal cord. This, of course, is not the original conception of Sturge and that subsequently held by Mackenzie. For them, visceral pain was due to spread of impulses in the cord to sensory tracts. It was hyperalgesia that was regarded as the result of normal impulses, such as those deliberately provoked, playing on