Response of subcutaneous vessels to venous distention.

SINCE the presentation of experimental evidence suggesting that a rise in venous pressure produces an increase in peripheral resistance, many reports have appeared regarding the site as well as the existence of such a response." The increased resistance to blood flow following venous distention has been explained by some workers as due to reflexly-induced arteriolar constriction through central connections and by others on the basis of a local response. The investigation reported here was undertaken to ascertain the site of vasoconstriction, if sucli occurred, by direct observation of subcutaneous vessels during venous distention. Observation of vessels in the wing of the bat offers many advantages for such a study. The method eliminates anesthesia and surgery, and is admirably suited for microscopic observation at high powers of magnification without disturbing the normal circulation or subjecting the animal to stress.