The action of nicotin on the ciliary ganglion and on the endings of the third cranial nerve / by J. N. Langley and H. K. Anderson.

  • Langley, J. N. (John Newport), 1852-1925.
Date:
[1892]
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Licence: Public Domain Mark

Credit: The action of nicotin on the ciliary ganglion and on the endings of the third cranial nerve / by J. N. Langley and H. K. Anderson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    required to paralyse each function, or by paralysing all and noting the time taken for each function to recover. In the rabbit we find the order of ease of paralysis is:— 1. Sphincter of iris. 2. Extrinsic muscles of the eye. 3. Elevator of the eyelid\ The action of the 3rd nerve (centrally of the ciliary ganglion) on the pupil is much more easily paralysed than its action on the extrinsic muscles of the eye. The minimal dose of nicotin is 5 J to 6 milligrams. The paralysis in this case is, however, but brief, it passes off in about a quarter of an hour. The nerve-cells of the fibres to the ciliary muscle are apparently paralysed at the same time as those of nerve-fibres to the sphincter iridis, but have not made accurate observations with regard to this. The other actions of the 3rd nerve require very nearly the same amount of nicotin to annul them, viz. about 10 milligrams, but we have found the raising of the eyelid^ to return a little earlier than the movements of the eye; sometimes also after a dose of 9 or 10 milligrams stimulation of the 3rd nerve will still cause elevation of the eye^ but will not cause contraction of the extrinsic muscles of the eye. As we have said, these actions cease in consequence of a paralysis of motor nerve-endings. When 10 milligrams of nicotin have been given, the normal effect on the iris of stimulating the 3rd nerve in the skull does not return for three-quarters of an hour to an hour, but a trifling effect may be visible much earlier; it is difficult to determine exactly when the 3rd nerve is beginning to recover its function, for there appears to be a first stage of recovery in which the contraction of the pupil on stimulating the 3rd nerve is so slow as to escape observation, and to be marked only by the somewhat smaller size of the pupil at the end of the stimulation. The pupillo-dilator nerve-cells of the superior cervical ganglion are paralysed less readily by nicotin than the pupil!o-constrictor nerve- cells of the ciliary ganglion, but they are paralysed a trifle more readily than the motor nerve-endings in the 3rd nerve in the extrinsic muscles of the eye. The following experiment will serve to show some of these points:— 1 When the thu-d nerve is stimulated with increasing strength of currents, starting with minimal, the elevation of the eyelid is first obtained, then the contraction of the extrinsic muscles of the eye, and lastly the contraction of the sphincter iridis. We have tried this on the dog only. 2 And protrusion of the nictitating membrane, cf. above p. 461.