Note on Regeneration of Præ‐Ganglionic Fibres of the Sympathetic

IN a former Paper IP have given an account of some observations on the origin fronm the spinal cord of the nerve fibres which are present in the cervical sympathetic, and of the peripheral distribution of the fibres derived from each spinal nerve. These observations-which in part confirmed and in part extended the results of others-showed that in the cat the first seven thoracic nerves sent nerve fibres to the cervical sympathetic; that the fibres of each nerve had its characteristic distribution. Thus the 1st thoracic nerve supplied the pupil and the nictitating membrane but sent few or no fibres to the vessels of the ear, and none to the hairs of the face and neck; the 2nd thoracic differed from the 1st in sending a considerable number of fibres to the blood vessels of the ear, and as a rule in sending more fibres to the nictitating membrane and fewer to the pupil; the 3rd thoracic sent a few fibres only to the puipil; the 4th thoracic sent none to the pupil, a few only to the nictitating membrane, but as a rule sent a few to the hairs of the face and neck; the 5th also sent no fibres to the pupil, very few and sometimes none to the nictitating membrane, but some to the vessels of the ear and to the hairs of the face and neck. The 6th and 7th thoracic supplied the hairs only, the 6th sending more fibres to them than the 7th. There is good ground for believing that all these fibres of the cervical sympathetic terminate in the superior cervical ganglion, the impulses they normally convey passing to the nerve-cells of the ganglion and so to the nerve-fibres given off by the cells. Suppose now that the cervical sympathetic is cut, and the ends are placed together. Presumably the cut peripheral fibres will regenerate. If they do, will they grow past the superior cervical ganglion, and form