Page:Popular Science Monthly Volume 21.djvu/189

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.
179
PSYCHOLOGICAL EXPERIMENTATION.

under the title "Idea of a New Anatomy of the Brain." In support of this statement Mr. Shaw cited certain passages from Bell's very scarce tract, which, read in the light of subsequent events, seemed an adequate justification of it. But, unluckily for the credit of both, a copy of the tract had found its way into the possession of a certain Mr. Alexander Walker, who had claims of his own to advance; and he re-printed it in full in a thin volume (now before me) published anonymously in 1839, under the title of "Documents and Dates of Modern Discoveries in the Nervous System."

I well remember the sensation which was produced at the time, among those who took an interest in the subject, by this publication; from which it plainly appeared that the fundamental conception enunciated in this "Idea" had gone no further than this—"that the nerves of sense, the nerves of motion, and the vital nerves, are distinct throughout their whole course, though they seem sometimes united in one bundle; and that they depend for their attributes on the organs of the brain to which they are severally attached"; while, in carrying out this conception, Bell, misled by his anatomy, had gone altogether wrong.

This doctrine was by no means new. It had been known from a very early period that our limbs can only feel or move (I use these words in their ordinary sense) by virtue of the nerve-trunks which connect their skin and muscles with the spinal cord, and through it with the brain. And although, when a limb is paralyzed, it is usually deprived at the same time of feeling and of motion, yet as cases were occasionally observed in which motion was lost without feeling, or (more rarely) feeling was lost without motion, the idea arose that two distinct sets of fibers may be bound up in the same trunks; one for feeling and the other for motion—or, as we should now express it more scientifically, one set conducting impressions made on the sensory surfaces toward the central sensorium, while the other transmits nerve-force from the motor centers of the nervous system to the muscles which it stimulates to contraction. This idea found distinct expression in the writings of certain ancient medical authors; and cropped up from time to time in modern medical literature, some writers approving it, while others dissented from it. And it was formally advanced in 1809 by Mr. Alexander Walker, who, in a paper entitled "New Anatomy and Physiology of the Brain in Particular, and of the Nervous System in General," published in the "Archives of Universal Science" for July in that year, argued that "medullary action" (or, as we should now say, a nerve-current) "commences in the organs of sense; passes, in a general manner, to the spinal marrow, by the anterior fasciculi of the spinal nerves, which are, therefore, nerves of sensation, and ascends through the anterior columns of the spinal marrow, to the hemispheres of the cerebrum," in which he located the sensorium commune. Thence he traced his "medullary action"