Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1845 edition. Excerpt: ... wrought more directly in the brain; if it be the fifth, or any of the nerves of the medulla oblongata, the stimulus acts directly on that part; but if a nerve of either limb be stimulated, the change must be propagated through the spinal cord. It will be asked, if this be the modus operandi in sensations, how does it happen that disease of one optic thalamus does not impair sensation in one-half of the body? And how is it that such disease is much more frequently accompanied by hemiplegic paralysis, of a kind not to be distinguished from that which depends on diseased corpus striatum? The answer to the first question is as follows. The optic thalamus, or more properly, the centre of sensation, is never wholly diseased, for this centre is not confined to the optic thalamus of descriptive anatomists, but extends to the mesocephale and olivary columns. Extensive disease of this centre would probably be fatal to sensation. But the most ample provision exists for opening up new channels of sensation if those on one side or a part of them be impeded. The centres of opposite sides are intimately connected, especially in the medulla oblongata and mesocephale, by commissural or by decussating fibres; the optic thalami of opposite sides are connected to each other by the posterior commissure and the soft commissure, and the immense multitude of fibres which radiate from each thalamus insure its connection with a considerable extent of the brain, so that a change in any part of it cannot fail to be communicated to some portion of the hemisphere. It is sufficient for mere sensation that the centre of sensibility should be affected. Intellectual change resulting from that affection depends upon the fibres which radiate between that centre and the...
