Page:Popular Science Monthly Volume 7.djvu/483

Rh the spinal cord, that is injured, all the nerves coming out from it are paralyzed; and, so long as the ganglion from which the respiratory nerves come is not affected, life is possible, however numerous the paralyses. Now, it appears that, for each of our functions, respiration, movements of the heart or of the eye, deglutition, etc., there is a special ganglion of the gray substance forming part of the central column, and. charged with the regular coordination of the movements necessary to the accomplishment of this function. Thus, e. g., in order to voluntary swallowing, it is first necessary that the will determine movements of deglutition, then that this order be transmitted to the nervous centre of deglutition, i. e., a small body of gray substance which anatomists have called the olivary body (on account of its form), and which presides over this function.

Between these two centres, however, of which one is producer and the other coördinator, there is a third, the centre of impulsion. The central gray substance, expanding in the brain, forms two large ganglions surrounded entirely by white substance, except at their base, which is connected with the central axis. These two large cerebral ganglions are called respectively the optic layers and the corpora striata. It is they that determine the motor impulsion, that transmit to such and such a ganglionic nerve-centre the order to put itself in motion. Thus the nervous influx arising from will proceeds from the superficial nerve-cells to the ganglionic centres of the brain, then to the ganglionic centres of the signal cord, issuing in regular movement. It is something like the case of an electric telegraph, with stations and intermediate relays.

Now, coming to aphasia, it seems to have been well established (from post-mortem examination) that there is a limited region of the superficial portion of the brain, on which the faculty of articulate language is dependent, and impairment of which gives rise to aphasia as understood by M. Broca. First of all, it is in the left hemisphere (a curious thing in an organ so symmetrical as the brain). Next, it is in the anterior part of this hemisphere; and, lastly, to be more precise, it is the third cerebral convolution. Agreeably with this, it is found that a great number of aphasic patients are paralyzed in the right side of the body. It must be understood that the nerve-fibres cross over from the left hemisphere.

We may regard the anterior convolutions of the left hemisphere as a sort of logopoietic, or word-forming apparatus, where the previously vague idea becomes precise and distinct, taking a word-form and becoming representative. Lordat distinguishes these two forms of intelligence as the interior logos and the exterior logos. It should be remembered that this conception is a pure hypothesis; but it is in accordance with the facts.

But, for a phrase thought by us to come to the ear of another, a second series of apparatus is required. This is the continuous chain