On dilatation of the pupil from stimulation of the cortex cerebri / by J. Herbert Parsons.

  • Parsons, John Herbert, Sir, 1868-1957.
Date:
1901
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Licence: In copyright

Credit: On dilatation of the pupil from stimulation of the cortex cerebri / by J. Herbert Parsons. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    anterior branch of the suprasylvian convolutions; and in the cat from the anterior part of the suprasylvian region and the adjacent part of the third external convolution. The effect is obtained more slowly from stimulating the cortex than from direct stimulation of the cervical sympathetic nerve, but the latent period is shortened, and more nearly approaches that of the cervical sympathetic, if the oculo-motor nerve has been previously divided. Franck concludes from this that the effect is of the nature of a dilemma, but this view cannot be considered proved in the absence of accurate measurements of the respective latent periods. Constriction of the pupils was occasionally obtained in the dog from stimulation of the median part of the 3rd external convolution —accompanied by widening of the palpebral aperture without projection of the eyes. Stronger stimulus invariably led to dilatation, which rapidly followed the transitory constriction. The stimulation of the corresponding fibres of the corona radiata invariably caused constriction, never dilatation nor epileptoid convulsions. Franck and Pitres confirm Beevor and Horsley in obtaining dilatation from excitation of certain parts of the internal capsule. Bechterew and Mislawski ,10), in investigating the centres for the secretion of tears, obtained also the usual effects of stimulation of the cervical sympathetic (dilatation of the pupil, retraction of the nictitating membrane, &c.) from excitation of the inner parts of the anterior and posterior divisions of the sigmoid gyrus in the dog. An extremely interesting observation is recorded by Sherrington(11). In bringing physiological experiment to bear upon current theories of the emotions, he performed “ appropriate spinal and vagal transection ” in the dog to eliminate “ the sensation of all the viscera and muscles below the shoulder.” He says :—“ the eyes were well opened, and the pupil distinctly dilated in the paroxysm of anger. Since the brain had been by the transection shut out from discharging impulses via the cei’vical sympathetic the dilatation of the pupil must have occurred by inhibition of the action of the oculo-motor centre.” II. Method. Experiments have been performed upon 2 dogs, 28 cats and 1 monkey. The animals were anaesthetised with A.C.E. mixture in a few of the earlier experiments, but with ether only in the majority. They were completely anaesthetised and insensitive to pain throughout the experiments. When the animal is spoken of as being ‘ lightly anaes-