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and muscu

The numerous and complicated train of diseases we are

Class IV.

The nervous now entering upon appertains to the highest function of function the visible beings; the possession of which emphatically dis- highest of tinguishes animals from plants, and the perfection of which beings: as emphatically distinguishes man from all other animals: these are the diseases of the NERVOUS FUNCTION; -which in the sphere of its activity, embraces the embracing powers of intellect, sensation, and muscular motion. of intellect, Each of these powers evinces diseases of its own, and will sensation, consequently lay a foundation for a distinct order, un- lar motion. der the class before us. While, as there are also other diseases that affect several of them simultaneously, we become furnished with a fourth order, which will complete the series.

All these diversities of vital energy are now well known All dependto be dependent on the organ of the brain, as the instru- ent on the ment of the intellectual powers, and the source of the the brain : sensific and motory. Though, from the close connexion and synchronous action of various other organs with the brain, and especially the thoracic and abdominal viscera, such diversities were often referred to several of the latter though forin earlier ages, and before anatomy had traced them satis- merly factorily to the brain as their fountain-head. And of other visce50 high an antiquity is this erroneous hypothesis, that it has not only spread itself through every climate on the

ascribed to


tures popu

lar language.

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Class IV. globe, but still keeps a hold on the colloquial language This ancient error

of every people ; and hence the heart, the liver, the still tinc spleen, the reins, and the bowels, generally, are, among

all nations, regarded either literally or figuratively, as so many seats of mental faculties or moral feeling. We trace this common and popular creed among the Hebrews and Arabians, the Egyptians and Persians, the Greeks and Romans; among every savage, as well as every civilized tribe ; nor is there a dialect of the present day that is free from it: and we have hence an incontrovertible proof that it existed as a doctrine of general belief at a time when mankind, few in number, formed a com

mon family, and were regulated by common notions. Corrected The study of anatomy, however, has corrected the by the

loose and confused ideas of mankind upon this subject; study of anatomy. and while it distinctly shows us that many of the organs

popularly referred to as the seat of sensation, do and must, from the peculiarity of their nervous connexion with the brain, necessarily participate in the feelings and faculties thus generally ascribed to them, it also demonstrates that the primary source of these attributes, the quarter in which they originate, or which chiefly influences them, is the brain itself.

We are speaking, however, of man and the higher
classes of animals alone; for, as the scale in animal life
descends, the organ of a brain is perpetually diminishing
in its bulk, till at length it totally disappears, and its
place is supplied by other fabrications, as we shall have
occasion to observe in the sequel of this introduction :
which will lead us to take a brief notice of the following
subjects :


III. THE INTELLECTUAL PRINCIPLE. Natural I. In man, and those animals whose encephalon apfigure and division of proaches the nearest to his in form, the brain is of an oval the brain. figure, surrounded by various membranes of different

firmness and density, and consists of three principal di

I. Nature of the

ramifications and

visions ; the cerebrum or brain, properly so called, the Class IV. cerebel or little brain, and the oblongated marrow. The first forms the largest and uppermost part ; the second brain, its lies below and behind ; the third lies level with the second and in front of it; it appears to issue equally out substitutes. of the two other parts, and in turn to give birth to the spinal marrow ; which may hence be regarded as a continuation of the brain communicating with its different parts by the aid of numerous commissures, the querbander of the German writers, and extended through the whole chain of the back-bone. They are similarly accompanied with a cineritious or ash-coloured substance which forms the exterior of the three first divisions, but the interior of the spinal marrow, and appears to derive its hue from the great number of minute vessels that appertain to it. According to Mr. Bauer's very delicate microscopic Substance

of the brain experiments, when the substance of the brain is made a

according subject of examination immediately after death * abun- to Bauer's dance of fibres”, to adopt the words of Sir Everard Home with the miin relating these experiments, "are met with in every croscope. ** part of it ; indeed it appears that the whole mass is a tissue of fibres, which seem to consist entirely of an aecumulation of globules whose union is of so delicate a nature that the slightest touch, even the mere immersion in water, deranges and reduces them to that mass of glo- and the prebules of which the brain appears to be composed when tion of Proexamined with less accuracy or under « less favourable chaska, and circumstances".—Mr. Bauer found that the globules of the Wensels. the brain, as well as those of pus, are exactly of the same size as those of the blood when deprived of their colouring matter*. And hence the doctrine of Prochaskat, and the Wensels I, respecting the globular form of the ultimate particles of the brain, seems sufficiently confirmed.

• See Sir Everard Home's Croonian Lecture, Phil. Trans. for 1818. † Opp. Min. Tom 1. p. 342.

De Structurà Cerebri, p. 24.

I. Nature of the

ramifications and

what: and

how pro



Class IV. Sir Everard Home from these microscopic disclosures,

endeavours to show that muscular fibres are minute chains brain, its

formed by an attachment of one globule of blood to

another : and that vascularity in coagula or extravasated substitutes. blood, or in granulations produced by pus, is effected by Muscular

the escape of minute bubbles of carbonic acid gass from the living fluid ; which hereby opens a path to a certain extent into the tenacious blood or pus that is ex

travasated or secreted. Origin of

From this general organ arises a certain number of long, whitish, pulpy, strings, or bundles of fibres, capable of being divided and subdivided into minuter bundles of filaments or still smaller fibres, as far as the power of glasses can carry the eye. These strings are denominated nerves; they are surrounded, to their extremities, by one or more of the common membranes of the brain, and, by their various ramifications, convey different kinds or modifications of living power to different parts of the body, keep up a perpetual communication with its remot

est organs, and give motivity to the muscles. Reason of As the brain consists of three general divisions, it of the brain

might, at first sight, be supposed that each of these is into distinct allotted to some distinct purpose; as, for example, that compart

of forming the seat of intellect or thinking; the seat of clearly the local senses of sight, sound, taste, and smell, and the known.

seat of general feeling or motivity. The investigations and experiments of Mr. C. Bell, and M. Magendie, to which we shall presently advert, pave the way to some important doctrines in respect to a few of these points, but leave us quite in the dark in respect to various others; and particularly as to the source of intellect; while it is difficult to reconcile even the doctrines which have thus been fairly deduced with the motific, and even with the sentient motific powers that must exist in numerous cases of an extensive disorganization of the brain and in acephalous animals. The first and second nerves and the portio mollis of the seventh sufficiently attest their exclusive uses as nerves of the special senses ; while the distribution of the greater part of the third, of the fourth, and of the

the division

ments not

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