Diseases of the skin : an outline of the principles and practice of dermatology / by Malcolm Morris.

  • Morris, Malcolm Alexander, Sir, 1849-1924.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Diseases of the skin : an outline of the principles and practice of dermatology / by Malcolm Morris. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

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    or reflected from the periphery, sets up a corre spending disturbance in the vaso-inotor centres in the spinal cord, with the result that the circulation at certain parts is thrown into disorder. The blush of shame and the pallor of fear illustrate the effect of mental emotion—i.e. disturbance of the higher cerebral centres—on the vaso-motor system, and through it on the skin. The rashes of fevers and the eruptions caused by certain drugs exemplify the action of the cerebro-spinal centres on the integument; these centres are in the first place irritated by the poisonous material circulating in the blood, and this irritation reacts through the vascular system on the skin. The effect of peri- pheral irritation is illustrated by the consequences which in some persons follow contact with certain species of hairy caterpillars. Intense local hyper- £emia, quickly followed by the development of a wheal, is the first result of the direct irritation of the sensory filaments. Soon, however, when the peripheral irritation has had time to make itself felt in the centres, an answering disturbance is excited in parts around the original seat of irri- tation, and this may reach such a pitch that scratching will at once bring out an abundant crop of similar lesions. A good example of reflex angio- neurosis is found in urticaria, in which the irritation of the pneumogastric nerve by the offending agent —e.g. shell fish in the stomach—is reflected from the centre to the skin. The character of the lesion produced by dis- ordered innervation in any particular case is to some extent a question of the degree of vascular disturbance ; but that other elements of a less simple nature are concerned in the process is proved by the fact that in varicella or pemphigus exudation may occur without precedent hypenemia.