The Neuro-Motor Mechanism of the Small Blood Vessels of the Frog

Abstract

The authors examined, by means of stimulation with a micro-electrode, the distr. of the contractile elements of the small blood vessels in the retrolingual membrane of the frog and concluded that the modified smooth muscle cells of the capillary are confined to the region of its origin. If the capillary branches before emptying into a venule, the branches are devoid of smooth muscle cells and do not contract. The region of the capillary origin may act as a unit with its adjacent blood vessels, but frequently it acts independently of them as a sphincter-like mechanism. Supporting evidence for this concept of the control of capillary blood flow is presented.