Selected monographs on dermatology / P.G. Unna [and others].

Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Selected monographs on dermatology / P.G. Unna [and others]. Source: Wellcome Collection.

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    on the other hand, have shown that the experimental pro- duction of arterial dilatation is very much facilitated by a previous strong constriction, such, e. g., as is caused by cold. The production of anaemia by cold, the blood-pressure being normal, accumulates, by compressing the endothelial nerves se, a latent stimulus for the inhibitory nerves ; and this becomes manifest when weak and otherwise ineffective stimuli are superadded. We have, moreover, already seen that the pallor due to external cold easily passes over to hyperemia in the case of the healthy skin (normal reaction of cold). This happens even when the blood-pressure is only a little raised, as, e. g., during quick awakening. It may also be caused by sensory stimuli, such as gentle rub- bing of the skin. All these events hence occur through the intermediation of the path se—m—g, and, as far as we can see, the assumption is sufficient of sensory endothelial nerves which are at the same time dilators, and of sensory muscle-nerves which are also constrictors of the cutaneous vessels. The former may be, considered to be identical with the nerves seen by the author and by Bremer. We have to thank the experiments of v. Bezold,1 and of Ludwig and Thiry,2 for our knowledge of the fact that stimulation of the central end of sensory nerves causes rise of blood-pressure, and that the latter is the result of the contraction of peripheral arteries. This process takes the path h—m—a. Heidenhain,3 much earlier, had observed a rise of temperature, i. e. dilatation of the cutaneous arteries, to follow stimulation of sensory nerves ; and this was not obtained after section of the vaso-motors. Snellen and Loven4 found, further, that stimulation of the central end of the auricular dilated the arteries of the ear, and that stimulation of the dorsal nerve of the foot dilated the saphenous artery. A sensory stimulus thus caused dilata- tion of the cutaneous artery supplying the same region, i. e. a reflex travelling by the path h—g. Finally, Goltz and Ostroumoff observed a rise of temperature, or arterial dilata- 1 ' Untersuchungen iibev die Innervation des Herzens,' Leipzig, 1863. ! ' Sitzb. d. Wiener Akademie,' 1864. 3 ' Pfluger's Archiv,' 1870, p. 504. 4 ' Sitzb. d. Sachs Akad. d. Wissensch.,' 1866.