. Johnson's new universal cyclopaedia : a scientific and popular treasury of useful knowledge. h of Schwann continuouswith those of the primitive fibre. The secomlary nerve-fibres thus produced arc individually smaller than the onefrom which they spring, but in the aggregate the thicknessof the branches is usually greater than that of the originalfibre. Still farther towards the periphery both the sheathof Schwann and the medullary sheath disappear, the lattersometimes before the former, and the axis-cylinder whichalone remains then divides and subdivide-s until it is brokenup into its primiti
. Johnson's new universal cyclopaedia : a scientific and popular treasury of useful knowledge. h of Schwann continuouswith those of the primitive fibre. The secomlary nerve-fibres thus produced arc individually smaller than the onefrom which they spring, but in the aggregate the thicknessof the branches is usually greater than that of the originalfibre. Still farther towards the periphery both the sheathof Schwann and the medullary sheath disappear, the lattersometimes before the former, and the axis-cylinder whichalone remains then divides and subdivide-s until it is brokenup into its primitive fibrils, which are extremely minute,.00002 or less in diameter, and often present a delicatebeaded appearance. Another variety of nen-e-fibres isfound in tlr. branches of the great sympathetic nerve,which, on account of the absence of the medullary sheath,have been called non-meduUated fibres (also Remaks fibres).These correspond in size for the most part to the mediumand smaller mcdulhited fibres, and when fresh are smoothor somewhat granular, often marked by faint longitudinal Fig. Remaks nerve-fibres. striations. They consist of a peripheral sheath, identicalwith that of the medullated nerve-fibres, enveloping abundle of primitive nerve-fibres united by a finely granularinterfibrillar substance. Such non-medullated fibres existalso in the olfactory nerves, and in the white matter of thebrain and spina! cord fibres are encountered which arc quitesimilar, except that they do not possess the peripheral sheathof Schwann. The medullated nerve-fibres of the brain andspinal cord are also destitute of the sheath of Schwann, to Fig. 8.
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