Sympathetic Vasodilator Fibers in the Upper and Lower Extremities

In 1890 Sewall and Sanford 1 found that placing one upper extremity in warm water induced vasodilatation in the fingers of the opposite hand. They estimated the blood flow to the digits by means of a plethysmograph. In 1911 Stewart 2 corroborated this observation by means of calorimetric determinations of the blood flow to the hand. More recently this phenomenon of indirect vasodilatation induced by heat has been studied carefully by several investigators, 3 and a great deal has been learned concerning the mechanism of its production. Pickering 3e first showed that in human beings vasodilatation induced in one extremity by warming another depends on the return of the blood from the warmed extremity to the general circulation. He estimated the blood flow to the hand calorimetrically. Gibbon and Landis 3b later showed that intermittent occlusion of the arterial and venous circulation of the extremity immersed in warm water prevents