Some Aspects of the Basal Tone of the Blood Vessels.

Summary. In experiments on cats the nature of the basal vascular tone that remains after sympathectomy has been analysed. The basal tone of the vessels of the skeletal muscles is quite marked while the vessels of the paw, with its abundance of arteriovenous anastomoses, become almost maximally dilated after constrietor fibre section. On the other hand, the latter type of vessels are more sensitive to known biogenic constrictor substances. No evidence of a release of vasotonic agents from the spleen could be obtained. It is therefore suggested that basal vascular tone can hardly be a consequence of circulating constrictor agents, but is probably a matter of smooth muscle automaticity, more or less pronounced in different regions depending on the degree of functional differentiation of the vessels.