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Intellection.

12*

INTELLECTION.

THE

HE higher orders of created beings are distinguished by the possession of certain faculties, which, if not exclusively belonging to animal life, are of very doubtful existence in the vegetable world. Sensation and voluntary motion, implying conscious individuality, are connected with the presence of a particular tissue or structure which we call the Nervous System, and which, gradually more and more fully developed, and becoming more and more complicated, is offered to our contemplation in its most varied and exquisite arrangements, in the highest and most perfect of all animals. It is here that man enjoys his peculiar attributes; by virtue of his superiority in this portion of his organism, he reigns supreme over all nature. Perception, thought, and action, in him immeasurably of loftier character than in all other creatures, are thus ele

vated by the infinite delicacy of the mechanism through which they are exerted: and yet this very delicacy, and the wide complication by which the human frame is rendered so full of varied capacities for action and enjoyment, serve also to admit morbid as well as normal impulses; to receive impressions of injurious and destructive influence as well as those which are kindly and favorable, and thus become equally ready and expanded inlets of disease.

The nervous system in man, and in animals resembling him, consists of a generating and conducting apparatus; a receiving centre, and communicating fibres. It generates the vis nervosa-nervous force, nervous power-an expression of an unknown faculty, which some regard as a fluid-an imponderable-of which heat and magnetism may be considered analogues. Many, indeed, believe it to be as closely related to them as they are to light and electricity; and, as some have urged plausible and ingenious reasons for the opinion that all these agents are in essence and substance absolutely identical, so there are not a few who unhesitatingly pronounce the nervous force to be nothing but the galvanic fluid, peculiarly modified by its source and mode of production.

It is impossible, in the present state of our knowledge, to speak of this power or faculty otherwise than by the use of hypothetical phrases; and, in the great diversity of views concerning its nature and origin, it is difficult to avoid falling into positive contradictions in the attempt to develop its functions, and the modes of their performance.

The apparatus to which it pertains is built up of numerous parts, so conjoined as to form a whole, of which the several structures composing it exercise different offices. To it, we owe the correspondence of the vital movements which carry on our individual existence; by it, we are brought into conscious relations with external nature. Its circumference, or peripheral portion, receives impressions made from without, in many diverse modes, some of which are transferred to the interior parts, and there acted on, or retained. Such portions as not only receive impressions and retain them, but generate force, are called centres; those which conduct or communicate impulses, are nerves. The matter of which it is constituted is of two kinds-one of which predominates in the centres; the other is found in the nerves: the former is darker-colored, gray, or cineritious; the latter is white. The centres are the brain, the spinal marrow, and the ganglions. The gray neurine or nervous matter is vesicular; the white is tubular. When the latter is prolonged and enclosed in a sheath, of a peculiar but delicate membranous tissue, it becomes a nerve. The offices of the nerve are various. Upon it, at its extremity, or, perhaps, even in some part of its course or the extent that lies between its central extremity and the organ or surface in or upon which it expands and loses itself, an impression is made, we know not how; in a like inconceivable manner it is conveyed by it to the centre with which it is connected. When this is the brain, it gives rise to what we call a sensation,

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