Library Collections: Document: Full Text

Tactile sensation proper is characterized by the feeling of the touch, or perception; the seat of the touch is the peripheric extremities of the nerves; but the seat of the feeling is the ganglion, intermediate terminus of the afferent nerves. Thence nerve fibres transmit the feeling to the hemispheres, and the different nerves transmit the will's orders to the peripheric organs of action. But the cerebral ganglia or hemispheres are not the seat of sensation. Their removal leaves a bird in a state of stupor, but it opens its eyes when it hears the report of a pistol, and then relapses into immobility; its sight is also retained, since it will sometimes fix its eyes on a particular object; and likely the perception of the other senses is retained, for it occasionally smoothes down its ruffled feathers, in which operation the sense of touch is involved.

On the other hand, that the sensorial ganglia are really the seat of sensation, is proven by the greater size of the one ganglion corresponding with the superior attainment of its function in each animal; as in man the relative outgrowth of the hemispheres above the sensorial ganglia is in proportion to the superiority of his imaginative and reasoning powers over his capacity of perception through the senses.

These relative differences explain the immense superiority of the intellectual faculties of man, and his inferiority to many animals in purely sensorial perceptibilities. These remarks identify the principle upon which our sensorial training shall be based -- that sensations take place from the peripheric extremity of a nerve to its centripetal ganglion; the first receiving the shock, the second the impression of the shock, through the nervous conductors.

We find illustrations equally beautiful and distressing of this analysis of sensation, when we compare an idiot whose eye cannot be struck by whatever image is presented to his blank sight, with another whose nerves transmit the impressions very slowly, and with another whose sensorium receives the impressions as defaced. This pathological analysis demonstrates equally well the point of the mechanism where the false image is formed in hallucination, and the process by which a slight, peculiar hesitation, previous to the utterance of speech, precedes by many months the confirmed symptoms of general paralysis.

But to limit ourselves closely to our subject, we insist upon this point, that the functions of the senses may be affected at their origin, along their course, at their centre, separately, or together. Let us state as a corollary, that the senses may be in themselves normal, yet left in the same state of impotence to perceive sensations, in which we have seen the motor organs incapable of moving, as if paralyzed, by mere deficiency of the will and of the intellectual synergy. This last incapacity may be more or less aggravated by sensorial ones.

From these observations, we shall be enabled to draw a few inferences that will have a practical bearing on the training of the senses.

We must make sure of the point or points where lies the deficiency of a nervous function. If it be at the origin we must cultivate the point of entrance of contacts, open the doors, enlarge or straighten the windows through which the objects of our sensations may come in contact with the peripheric extremity of the apparatus. If it be in the centripetal nerves, we must submit them to series of exercises of quickness borrowed from those of personal imitation; gentle Faradization may do good in some instances. If the sensorial ganglia lack sensitiveness we provoke them to such alternate, abrupt feelings that these cannot fail to be perceived; we move and stimulate them by contrasts. If the senses, though correct, do not receive impressions because they are not lighted by comprehension, we must come down, down again till we find the object of our sensorial, or better qualified, intellectual teaching, among and next to the very lowest things that the child understands. And if the want of impression originates in the deficiency of the will, we must create a desire; the thing desired shall stamp its impress on the awakened senses, and soon be looked for by the child. Practice alone can suggest the whole of the special rules of which the above are only generalizations.

But there is a principle in which culminates all the training of the functions, particularly of those of the senses; principle, whose full comprehension or ignorance determines the issue of all our efforts. This principle is that each function of the life of relation is virtually, can and must be made effectively, identical with its faculty; in other words, that each function is psycho-physiological.

This law, demonstrated in animals as well as in man, is not subject to exceptions even in idiocy. In the natural state animals elicit the highest degree of instinctive acuteness or even of comprehension from the use of their most perfect senses; but under the artificial training of schools and colleges the sensorial and intellectual developments of children appear quite disconnected, nay, are effectively rendered antagonistic; the overcultivation of one causing the drooping of the other; the exclusive training of the function impairing the faculty, the exclusive training of the faculty atrophying the function. Contrarily to this practice we say, the exercise of each function must give rise to a corresponding exercise of the complementary faculty; and at the present stage of this exposition we say more: Each sense must be taught as a function, and taught besides as a faculty.