The nervous system / By Ludovic Hirschfeld, .... Edited in English by Alexander Mason Macdougal,... , with artistically coloured lithographic illustrations, designed by J. B. Léveillé.

Ludwik Maurycy Hirszfeld

Date:: [1867]

Credit: The nervous system / By Ludovic Hirschfeld, .... Edited in English by Alexander Mason Macdougal,... , with artistically coloured lithographic illustrations, designed by J. B. Léveillé. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

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$CENTRAL NERVOUS SYSTEM. A.-EHCEPHALON OR BRAIN. The brain is all that part of the nervous centre which is enclosed in the cranial cavity, and constitutes the superior portion of that centre. It is a soft, whitish and greyish mass, ovoid, irregularly flattened in a part of its extent, and having the posterior extremity more bulky than the anterior. Volume.—The mass of the brain, which is proportionably more considerable in man than in animals, is, in like manner, greater in the child than in the adult, in the male than in the female, but it becomes atrophied in old people. Its configuration is relative to that of the cavity which contains it. Dimensions.—The size of the brain is, on an average, 16 centimetres1 in its longitudinal, 13*5 centimetres3 in its transverse, and 12 centimetres3 in its vertical diameters ; but this last admeasurement is applicable only to the middle portion, where the brain presents its greatest development. Weight.—Its average weight in the male is 1468 kilogramme,4 and in the female 1'345 kilogramme.5 General appearance.—Independently of the osseous case which environs it on all sides, the brain is in relation with a triple membranous envelope {meninges) which surrounds it entirely. Stripped of its membranes, it is observed to be channelled over its whole surface by a great number of furrows, more or less deep, which circumscribe as many oblong elevations variously contorted: the furrows are called anfractuosities {sulci), the elevations convolutions {gyri). The brain is composed of three portions: the cerebrum, the cerebellum, and the mes- encephalum. There may be distinguished in it a superior and external region (convexity), irregularly convex, which corresponds to the cranial vault; an inferior region (base), alternately convex and concave, which reposes upon the base of the cranium ;6 and lastly, an internal region. The convexity is exclusively constituted by the cerebrum; the base, by the cerebrum, the cerebellum, and the mesencephalum, which communicate between themselves and with the medulla spinalis, by means of prolongations called peduncles; while the internal region, straight and vertical, forms with that of the hemisphere of the opposite side, the vertical antero-posterior median fissure. 1 Very nearly 6'3 inches. 2 A trifle over 53 inches. 3 Somewhat more than 4'7 inches. 4 3 lbs. 3oz. 12-524 dr. avoirdupois. 5 2 lbs. 15 oz. 7105 dr. avoirdupois. 6 It is well to observe here, that the base of the brain—excepting, perhaps, the part over the orbital plates of the frontal bone—does not come into apposition with the corresponding portion of the skull, the membranes only intervening, but is separated from it by a stratum of cerebro-spinal fluid, forming a species of water- bed ; which, in coadjuvancy with the disposition of the internal layer of the dura mater, protects the delicate nervous substance from contact with the hard surface, and from collision with the salient projections there situate, as well as prevents that unequable distribution of pressure upon the vessels in that region, which would otherwise occur. Indeed, the whole nervous axis with its immediate investing meninx, would, on con- sideration, appear to be suspended in the fluid enclosed by the arachnoid, in such a manner, that the excess of weight, representing the sum of the difference between the specific gravity of the former as a whole and that of the latter in an equivalent bulk, is sustained by the connecting medium between the two membranes; so that, no matter where upon the surface of the nervous mass vessels may be situate, or what posture the body may assume, the pressure upon them holds a like proportion at the same moment. This beautiful arrange- ment, which, by means of a greater elongation of the connecting medium between the membranes, admits of the accumulation of sub-arachnoid fluid in larger quantity beneath the lower part of the brain, and more particularly at the localities termed confluences, has received additional interest from the consideration of the mode in which vibrations propagated along the cranial parietes converge towards the bony processes of the base, and are there lost by dispersion in this fhiid,—as has been very clearly and admirably shown by Mr. Hilton (vide Notes from his Lectures On the Cranium, edited by Dr. Pavy); thus rendering, what would at first sight appear to be a conformation fraught with danger to the nervous centre, an element of the greatest security to it.$