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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    the pupil being said to be a quarter, a half, three-quarters, or fully dilated. This method of stating the results has been adopted in some of the protocols. The amount of light falling upon the eyes was usually fairly constant throughout the experiment, being diffuse London sunlight. In a few experiments performed on dark winter afternoons, a powerful (16-candle) electric light, placed about 3 feet off in the middle line in front of the animal’s head was used. It is only important to keep the light fairly constant. III. Localisation. As will be seen from the historical resume, both dilatation and constriction of the pupils have been described as results of cortical stimulation. The former is easy to demonstrate, the latter much more difficult. Most observers have regarded the effects as inconstant, and but little attention has been specially directed to them. Thus Ferrier includes dilatation of the pupil with salivation from the submaxillary gland, changes in pulse and blood-pressure, and “ other indications of general reverberation throughout the organism.” He regards them as “ merely complications, and not as results of localised cortical stimu- lation.” On the other hand, Bechterew and Mislawski conclude that “stimulation of the given regions of the cortex and of the optic thalmi has hit off the central endings (Verlangerungen) of the cervical sympathetic”; and that “the chief reflex centre for secretion of tears lies in the optic thalmi, and that there too are found the central tracts of the cervical sympathetic, their prolongations (Fortsetzungen) being continued thence to the cortex.” Franc^ois-Franck is careful to distinguish between two causes of dilatation of the pupil resulting from cortical excitation. One is a special and localised effect following stimulation of definite foci of the cortex, and also obtained from excitation of the underlying fibres of the corona radiata and internal capsule. The other accompanies epileptoid convulsions resulting from the stimulation of any and every part of the motor areas, and is never obtained from the underlying white matter, which does not induce the epileptic state. To the latter he attributes the dilatation after admini- stration of curare, which was observed by Bochefontaine. He perhaps lays too great stress upon this as a fundamental distinction, for it applies equally to other motor effects induced through the cortex. I have not paid much attention to any movements other than those