Muscle Tension and Reflexes in the Earthworm. by A. R. Moore

I t was first shown by Friedl~inder ~ that a decapitated piece of earthworm would perform normal peristalsis, with perfect coordination between the segments, if it were pulled forward over a rough surface. This experiment proved that the brain was not necessary to locomotion but did not dearly decide the question as to whether the impulse to movement was given by sensory stimulation of the integument in contact with the surface or by tension of the muscles themselves as the result of pulling. The first possibility, namely, contact stimulation of the integument, has been shown t o be sufficient cause to initiate peristalsis in a suspended preparation of the worm. 2 On the other hand, if sensory stimulation of the dermal layer could be avoided it would be possible to test the value of muscle tension alone as a cause of peristalsis. For this purpose it is only necessary to put the worm into an M/8 solution of MgC12, allowing it to remain until there is no response to the stroke of a moist camel's hair brush. If a piece of suitable length be cut from the median portion of the worm and arranged in the usual fashion for making a kymographic record, the effect of tension in initiating peristalsis can be demonstrated. I t should be noted at the outset that no spontaneous contractions occur and that stroking the preparation with a brush does not initiate peristalsis. Next, let a weight be attached to the lower end of the piece so as to exert a tension of 1 or 2 gm. The extension resulting from the force of the weight is immediately followed by further active extension of the worm for a