The present paper deals, firstly, with an in vitro determination of impedance of large sections of carotide arteries. These experiments were thought of as a complement to our earlier experiments on the living animal. Their results can also be explained by a diminished damping factor, when the vascular muscles are brought into a contracted state. In some further experiments, pressure alone was recorded; the vessel was connected to a pump with sinusoidal movement of its piston, as in the first series of experiments. If the pump is set in such a position that, at the beginning of its movement, the piston is near the entrance for the artery attached to it, and when the vessel is inactive, the pump will produce pressure waves whose maxima will coincide with the static pressure before the onset of pumping. On the other hand, if the vessel is brought to an excited state by application of histamine, the pressure maxima exceed the pressure at rest. We conclude, therefore, that an excited vessel will produce additional forces or tension when it is quickly stretched and will follow the stretch, even when the frequency of these stretches is as high as 1 to 4 cps.