The rhythmically contractile veins of the Bat's wing possess suitable properties for recording in situ the activity of perfused peripheral vascular smooth muscle by means of a photometric method.

A physiological solution C.S.3., determined from the serum analysis, is used to replace the blood by perfusion. It is thus possible to investigate directly the influence of several haematological, pharmacological and physical parameters, on peripheral smooth muscle function and autoregulatory flow mechanisms, in the absence of any influence from the surrounding circulation.

Extra-systoles and extra-diastoles may participate in aiding flow. The latter exert a suction pressure by reversing the normal sequence of contraction. Both these responses may be reproduced experimentally by simulated intravascular pressure changes.

Visco-elastic properties of the vessel wall play an important role in determining the form of contractile response to different stimuli in vivo.

Denervation modifies the activity of a venous segment, isolated from the arterial pole by means of an anastomosis.

Some doubt is cast as to the presence of Nabased action potentials. Contractions cease immediately in calcium-free (+ EGTA) C.S.3. solution. In the absence of EGTA, this reaction is complete only after approximately one hour of perfusion.