Ashley W. Oughterson

STUDIES ON THE COURSE OF VASOMOTOR FIBERS AS MEASURED BY THERMIC CHANGES IN THE FEET AFTER ARTERIAL LIGATION AND SECTION OF THE SPINAL CORD AT VARIOUS LEVELS

In a previous paper (7) it was shown that in dogs under amytal anesthesia, ligation of both femoral arteries proximal to the profunda branch caused a decrease in the temperature of the feet which was interpreted as indicating a diminution of blood flow. The temperature of the feet remained at this lower level for several hours following which there was a spontaneous rapid rise indicating the development of collateral circulation. The rapidity of this response was taken as evidence suggesting that the reestablishment of former conditions by collateral circulation is a vasomotor phenomenon. It was found furthermore that decrease in the temperature of the feet following ligation of the femoral artery as above, could be prevented by removal of the tributary sympathetic ganglia, or if the temperature had already decreased to the level of that of the room, removal of the sympathetic ganglia immediately induced a rise in the feet to the previous level. This suggested that the rapid spontaneous return of the circulation following ligation of the femoral artery was a vasomotor phenomenon controlled by means of the sympathetic nervous system. In another paper (3) experiments were reported in which the same method was used. Following transection of the spinal cord at the level of the first lumbar vertebra, no increase in the temperature of the limb was observed. Gaskell (2), Bayliss and Bradford (1) and Langley (4, 5, 6) have stated that in an animal with seven lumbar vertebrae the connector fibers to the sympathetic ganglia supplying the posterior extremity are contained in the 11th, 12th and 13th thoracic and the 1st, 2nd and 3rd lumbar spinal roots. Since the results of the above (3) experiments did not coincide with their findings it seemed desirable to conduct further experiments to determine the effect of transection of the spinal cord at various levels.