Flow to the Extremities

T HIS STUDY Was undertaken to explore the extent of autonomic control of blood flow to the hands and feet. That is, to examine the question-is blood flow to the hands and feet at low ambient temperatures still regulated by the thermal state of the body as a whole, or is blood flow to the hands and feet determined by the known direct constricting effect of cold upon their blood vessels? Since the experiments of Sir Thomas Lewis in 1931 (I) there has been a growing understanding that vasodilatation may be produced in the extremities by heating other body areas. An intact sympathetic outflow to the extremity has been shown to be necessary for this reaction (I, 2). Pickering (3) suggested that the vasodilatation is the response to the circulation of warmed blood through the central nervous system, since it does not occur when the part heated is small or its circulation occluded. These observations have been confirmed repeatedly (4, 5). Recently, Miller has been able to prevent freezing of the rabbit’s ear for two hours at-55°F. by warming the animal’s body (6). The experiments reported herein reveal that a similar protection is available to the extremities of man. Inversely, Ferris and his co-workers (7) in particular have demonstrated that when the body is cooled, heating only the hand will not increase its blood flow over that of a non-heated hand