the brain is cut, it is found to be composed of two substances, essentially different in construction and function — the cortical and the medullary. The first is small in quantity, and principally concerned in the food and reproduction of the animal, and the cineritious in a great measure the register of the mind. Brute strength seems to be the character of the former, and superior intelligence of the latter. There is, comparing bulk with bulk, less of the medullary substance in the horse than in the ox — and in the dog than in the horse — and they are characterized as the sluggish ox, the intelligent horse, and the intellectual and companionable dog.
the medullary substance proceed certain cords or prolongations, termed
nerves
, by which the animal is enabled to receive impressions from surrounding objects and to connect himself with them, and also to possess many pleasurable or painful sensations. One of them is spread over the membrane of the nose, and gives the sense of smell; another expands on the back of the eye, and the faculty of sight is gained; a third goes to the internal structure of the ear and the animal is conscious of sound. Other nerves, proceeding to different parts, give the faculty of motion, while an equally important one bestows the power of feeling. One division, springing from a prolongation of the brain, and yet within the skull, wanders to different parts of the frame, for important purposes connected with respiration or breathing. The act of breathing is essential to life, and were it to cease, the animal would die.
are other nerves — the sympathetic — so called from their union and sympathy with all the others, and identified with life itself. They proceed from a small ganglion or enlargement in the upper part of the neck, or from a collection of minute ganglia within the abdomen. They go to the heart, and it beats; and to the stomach, and it digests. They form a net-work round each vessel, and the frame is nourished and built up. They are destitute of sensation, and they are perfectly beyond the control of the will.
We have been accustomed, and properly, to regard the nervous system, or that portion of it which is connected with animal life — that which renders us conscious of surrounding objects and susceptible of pleasure and of pain — as the source of intellectual power and moral feeling. It is so with ourselves. All our knowledge is derived from our perception of things around as. A certain impression is made on the outward fibres of a sensitive nerve. That impression, in some mysterious way, is conveyed to the brain; and there it is received — registered — stored — and compared; there its connections are traced and its consequences appreciated; and thence a variety of interesting impressions are conveyed, and due use is made of them.
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