The contractile blood vessels of the earthworm, Lumbricus terrestris

Abstract

1. 1. In intact resting earthworms the rate of contraction of the dorsal vessel is 11 beats/min; in “exercised” animals, 17 beats/min. 2. 2. In dissected animals the rate averages 8 beats/min, each contraction consisting of a peristaltic wave passing anteriorly. 3. 3. The contraction wave has a uniform velocity of 2·4 cm/sec posterior to the lateral vessels but the velocity becomes progressively less in the region of the lateral vessels. 4. 4. Each lateral vessel possesses an endogenous rhythmicity but can be driven by activity in the dorsal vessel. 5. 5. Increased intralumenal pressure increases the rate of beating of the dorsal vessel; decreased intralumenal pressure decreases the rate. 6. 6. Electrical stimulation of the dorsal vessel elicits propagated contraction waves but there is a long refractory period following each contraction so that the dorsal vessel cannot be driven in a one-to-one manner at a rate greater than once every 4 sec.