STUDIES IN DENERVATION: F.-THE CIRCULATION IN THE SKIN OF THE PROXIMAL PARTS OF THE LIMBS.

THE influence of the vasomotor nerves on the circulation in the fingers and toes is readily demonstrable and has been extensively studied. It is, however, much more difficult to demonstrate the nervous regulation of the circulation in the skin of the proximal parts of the limbs and relatively few observations bearing on this aspect of the circulation have been recorded, while only Grant and Holling (1937-8) have made it the object of detailed study. These authors found that very intense warming of the body produced an increased flow of blood in the skin of the limbs proximal to the hands and feet and by their method of occluding the circulation distal to the points under observation they were able to show that this increase was local and not merely a reflection of the changes occurring more peripherally. They then made experiments to elucidate the nature of this vasodilatation. They demonstrated that body warming failed to cause this vasodilatation after section of the sympathetic nerves or after cutting or blocking the local nerve supply of the skin. They next demonstrated that a local nerve block when the subject was cold did not cause a vasodilatation such as results in the digits and they made the complementary observation showing that a nerve block in the presence of vasodilatation caused a vasoconstriction. From these facts they concluded that the blood vessels of the skin of the proximal part of the limbs are supplied by vasodilator nerves of sympathetic origin. In reporting their observations Grant and Holling ieft two points for future clarification. The first of these was in regard to the importance of the part played by the activity of the sweat glands in determining the vasodilatation, though it was considered that this was likely to be small because a temporal coincidence of sweating and vasodilatation was sometimes absent. The second question related to explanation of the vasodilatation which they observed in the skin of the proximal parts of the limbs for the first week following sympathectomy. It is the purpose of this paper to record results substantiating those of Grant and Holling and to contribute to the solution of these two problems.