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Occasionally the other limb becomes gangrenous. On the other hand, the glycosuria may diminish or may even disappear after amputation. #Gangrene associated with Spasm of Blood Vessels.# #Raynaud's Disease#, or symmetrical gangrene, is supposed to be due to spasm of the arterioles, resulting from peripheral neuritis.
The most common form of capillary angioma is the nævus or congenital telangiectasis. #Nævus.# A nævus is a collection of dilated capillaries, the afferent arterioles and the efferent venules of which often share in the dilatation. Little is known regarding the etiology of nævi beyond the fact that they are of congenital origin.
Any drug or substance that raises the blood pressure by stimulating the vasomotor center or the arterioles, when constantly repeated, will be a cause of hypertension. This is particularly true of caffein and nicotin. Also, anything that might stimulate, or that does stimulate, the suprarenal glands will cause a continued high blood pressure. Pharmacol. and Exper.
Fact was not substituted for conjecture until about the year 1851, when the great Frenchman Claude Bernard conclusively proved that at least one chief function of the sympathetic fibrils is to cause contraction of the walls of the arterioles of the system, thus regulating the blood-supply of any given part.
If small hemorrhages occur in the arterioles of the extremities, of course the prognosis is not serious. Sometimes some of the smaller vessels of the brain may become obstructed and cerebral degeneration occur.
Under normal conditions the main arterial trunks supply their respective organs, the little connecting arterioles playing an insignificant part. But let the main supply-trunk be cut off or stopped for whatever reason, and a remarkable thing takes place.
Ten years earlier Henle had demonstrated the existence of annular bands of muscle fibres in the arterioles, hitherto a much-mooted question, and several tentative explanations of the action of these fibres had been made, particularly by the brothers Weber, by Stilling, who, as early as 1840, had ventured to speak of "vaso-motor" nerves, and by Schiff, who was hard upon the same track at the time of Bernard's discovery.
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