THE INNERVATION OF THE HEART OF THE ELASMO-BRANCH, SCYLLIUM CANICULA

¹ From the Zoölogical Station, Naples, and the Physiological Laboratory of Boston University School of Medicine

1. Two branches of the vagus go to the heart of Scyllium canicula, each carrying afferent and efferent fibers, one from the post-branchial ramus of the fourth branchial division (fifth branchial nerve), and the other from the main visceral trunk.

2. No acceleration of the rate of the heart occurred on faradic stimulation of the medulla, spinal cord, or first large sympathetic ganglion with the vagi cut.

3. No slowing of the rate of the heart occurred, due to lowering of tone in an accelerator center, on reflex excitation of the cardio-inhibitory center with the vagi cut.

4. Both morphological and physiological evidence indicate the lack of accelerator fibers to the heart of the elasmobranch.

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