Copy 1, Volume 3

The study of medicine / By John Mason Good ... Improved from the author's manuscripts, and by reference to the latest advances in physiology, pathology, and practice.

  • Good, John Mason, 1764-1827.
Date:
1840
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Licence: Public Domain Mark

Credit: The study of medicine / By John Mason Good ... Improved from the author's manuscripts, and by reference to the latest advances in physiology, pathology, and practice. Source: Wellcome Collection.

    12/506 (page 6)
    Class IV. I. Nature of the brain, its ramifications and substitutes. The remarks of Sir Charles Bell upon this subject, are well entitled to attention. “The trigeminus, or fifth nerve, says e, “ bestows upon all the surfaces of the head and face, externa anc internal, that sensibility which is enjoyed by the rest of the bocy through the spinal marrow*;” and, in proof of this, he descii es various experiments which show that, on dividing its branch to te cheek and lips, or on its destruction by disease, insensibility in- stantly takes place in these organs. Yet some of its branc ies prove motific as well as sensific, and draw the muscles of the eye into a state of mutual action to expel offensive particles that have found admission to its surface : while, of the nine nerves that proceed from the.brain, constituting the whole number that thus originate, six of them are distributed in a greater or less proportion to the single organ of vision; and co-operate in giving perfection to its powers; as the third, fourth, part of the fifth, sixth, and sevent 1. Several of these phenomena may, indeed, be resolved, though not the whole, into that close interunion which some parts of the brain maintain with other parts by means of ganglions, commis- sures, and decussations of nerves ; whence injuries on one side are often accompanied with loss of motion or feeling in the organs of the other side. So the curious and ingenious experiments, insti- tuted by Dr. Philip +, and to which we shall have occasion to return presently, sufficiently prove, that stimuli of a certain kind, as spirit of wine, applied to the posterior part of the naked brain of an animal, produce the same effect on the heart, and equally in- crease its action, as if applied to the anterior part, lo affect the heart, however, it seems necessary that the stimulus should spread over a pretty large extent of the brain ; so as to take in, by the rana-e of its excitement, some of the ganglions of the brain, whose office, as Dr. Philip conceives, is “ to combine the influence of the various parts of the nervous system, from which they receive nerves, and to send off nerves endowed with the combined influ- ence of those parts.” % He hence accounts for some organs of the frame being affected by every part of the nervous system, and others by only certain small parts of it; and the wide influence pos- sessed by the great sympathetic nerve, which is less a single nerve, than a string of ganglions. We are also hereby shown why the intestines, like the heart, sympathise with every portion of the nervous system. Fanciful to From all this, however, it is clear, that there is much yet to be pretend subdi- ]earnt concerning the actual arrangement of the brain, or of its visions inscru- * Phil. Trans., 1823, pp. 289, 290. f Phil. Trans., 1815. pp. 5—90. } Phil. Trans., 1815, p. 436. An opinion formerly prevailed, that ganglia were intended to cut oft' sensation ; but Sir Charles Bell noticed, that every one of the nerves, which he took to be instruments of sensation, had ganglia on their roots. “ Some very decided experiment,” he says, “ was necessary to overturn this doo-ma. I selected two nerves of the encephalon; the fifth, which had a ganglion, and the seventh, which had no ganglion. On cutting across the nerve of the fifth pair on the face of an ass, it was found, that the sensibility of the parts, to which it was distributed, was entirely destroyed. On cutting across the nerve of the seventh pair on the side of the face of an ass, the sensibility was not in the slightest degree diminished. By pursuing the enquiry, it was found that a ganglionic nerve is the sole organ of sensation in the head and face ; and thus my opinion was confirmed, that the ganglionic roots of the spinal nerves were the fasces or funiculi for sensation.” C. Bell’s Nat. Syst. of the Nerves, p. 34.—Ed.