. Quain's elements of anatomy . stbranches the perineurimn generally becomes reduced to a singleconnective tissue lamella, covered on both surfaces by epithelioid this condition it is sometimes known as the sheath of Henle. Both the cerebro-S]3inal and the sympathetic nerve-trunks are con-structed in the manner above described, but the fibres of the cerebro-spinal nerves are chiefly of the white or medullated kind, while in nervesbelonging to the sympathetic system non-meduUated fibres for the mostpart jjreponderate. But very few nerves are composed exclusively of oneor the other kind
. Quain's elements of anatomy . stbranches the perineurimn generally becomes reduced to a singleconnective tissue lamella, covered on both surfaces by epithelioid this condition it is sometimes known as the sheath of Henle. Both the cerebro-S]3inal and the sympathetic nerve-trunks are con-structed in the manner above described, but the fibres of the cerebro-spinal nerves are chiefly of the white or medullated kind, while in nervesbelonging to the sympathetic system non-meduUated fibres for the mostpart jjreponderate. But very few nerves are composed exclusively of oneor the other kind of fibre. The cerebro-spinal nerve-trunks and their branches always present abrilliant whitish aspect, whereas the sympathetic nerves vary inappearance, some being whiter, others grey or reddish in colour. Themore grey-looking branches or bundles consist of a large number ofthe pale fibres mixed with a few of the medullated kind (fig. 152) ; thewhiter cords, on the other hand, contain a proportionally large amount of Fig. Fig. 152.—A SMALL BUNDLE OF NERVE FIBRES ER03I THE SYMPATHETIC NERVE. (Key and ) The bundle is composed of pale nerve-fibres, with tlie exception of tlie fibre m., m,■whicb is enclosed here and there by a thin medullary sheath ; n, n, nuclei of pale fibres. meduhated fibres, and fewer of the gTey ; and in some parts of the nervegrey fasciculi and white fasciculi, respectively constituted as abovedescribed, run alongside of each other in the same cords for a consider-able space without mixing. This arrangement may be seen in some of thebranches of communication with the spinal nerves, in the trunk or cordwhich connects together the principal chain of sympathetic ganglia, andin the primary branches proceeding from thence to the viscera. In thelast-mentioned case the different fasciculi get more mixed as theyadvance, but generally it is only after the white fascicuK have passedthrough one or more gangha that they become thoroughly blended with
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