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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    sensory vascular depressor nerves, and reasoning by analogy, these authors assume the existence of similar sensory anta- gonistic constrictor fibres, which, when the vessels are di- lated, produce a regulatory contraction by stimulation of the vaso-motor centre. This path, se—m—a, constructed, as it were, for the sake of symmetry, may be considered super- fluous, since its existence is not proven. We can conceive the same effect to be produced in a simpler manner—by the expansion of the vascular tube stimulating directly the sen- sory nerve-endings situated in the stretched muscle-tissue, and thus reflexly causing a degree of contraction correspond- ing to the amount of expansion. We then have need only of the path sm—a, which we have already used to account for the vaso-constriction after section of the vaso-motors, to explain, without making use of the centres in the cord, all those cases of constriction which originate from the interior of the tube itself. This assumption of only two kinds of sensory nerves in the vessels, viz. endothelial- and muscle-nerves, suffices for all experimental as well as pathological facts hitherto observed. The former, stimulated by pressure of the blood or of the vascular wall, produce contraction reflexly through the cord centres ; the latter, stimulated by the stretching or tension of the vascular wall, cause a muscular contraction purely peripherally and directly. The gradual rise of pres- sure, increasing and diminishing rythmically with the heart- beat, is the natural stimulus of the inhibitory ganglia, by the path se—m—g, and it produces the dilatation of the arteries. The rapid and maximum expansion of the arterial wall, which occurs during arterial blood transfusion, leads (by the path sm—a) to so energetic a reaction in the direc- tion of constriction, that complete occlusion of the arteries may x-esult (Cohnheim). The gradual constriction of the cutaneous arteries when blood-pressure is falling (vide Anaemia) occurs without pres- sure on, and stimulation of, the sensory nerves (se), and is therefore chiefly due to the toxic action of m and g, which accommodates the tension of the arterial wall to the dimi- nished internal pressure. The investigations of Bernstein,1
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