Have we two brains or one?

  • Brown-Séquard, Charles-Edouard, 1817-1894.
Date:
[1890]
Catalogue details

Licence: Public Domain Mark

Credit: Have we two brains or one?. 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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    nervous apparatus is normal, which clearly shows that the pyra- mids are not the only, and not even the principal, channels by which irritations applied to the supposed motor cerebral zone are transmitted to muscles. In experiments, which for lack of space I cannot describe, I have ascertained that the effects of an irritation of the various parts of the base of the brain cannot, in the least, serve to estab- lish what is the place of passage of ordinary voluntary motor impulses in those parts. All of them produce, in most instances, movements in the corresponding, and not—as should be—in the opposite, side, even when the part irritated is the anterior pyra- mid just above the spot where its fibers pass into the other side. Still more, if I divide transversely the anterior pyramid, or the whole lateral half of either the medulla oblongata or the pons Yarolii, and then irritate one or the other of the two surfaces of the section, i. e., the one yet in normal connection with the brain or the other normally united with the spinal cord, the same movements appear almost always on the side of the irritation, showing that in both cases a reflex action of the uninjured side of the brain is produced. I ought to say that a mechanical irrita- tion causes the same effects as a galvanic one, so that it cannot be supposed that it is owing to a diffusion of a galvanic current that these curious phenomena occur. In presence of such facts, we can certainly state that nothing remains of one of the most important foundations of the doctrine that the motor nerve fibers of one side of the body proceed exclusively from the other side of the brain. VI. An argument similar to the preceding has been employed by clinicians to show that one side of the brain must be the mover of the opposite side of the body; it is the frequency of convulsions in the limbs or face on the side opposite to that of a lesion of the psycho-motor centers. The question should have been enlarged and put as follows: What are the relations between the various parts of. one of the cerebral hemispheres and unilat- eral convulsions? In a paper I read at the meeting of the British Medical Association, at Cambridge, England, in 1880, I gave a number of conclusions drawn from more than 500 cases of uni- lateral convulsions due to brain disease, showing how various