. Elements of histology. Histology. no Elements of Histology. [Chap. xiv. when pressure or reagents are applied to the fresh nerve-fibre. 144. Medullated nerve-fibres without any neuri- lemma, and consequently without any nodes of Ranvier, with a thick more or less distinctly laminated medul- lary sheath, form the white substance of the brain and spinal cord. In these organs, in the hardened and fresh state, numerous nerve - fibres may be noticed, which show more or less regu- lar varicosities, owing to local accumulations of fluid between the axis cylinder and medullary sheath. These are call
. Elements of histology. Histology. no Elements of Histology. [Chap. xiv. when pressure or reagents are applied to the fresh nerve-fibre. 144. Medullated nerve-fibres without any neuri- lemma, and consequently without any nodes of Ranvier, with a thick more or less distinctly laminated medul- lary sheath, form the white substance of the brain and spinal cord. In these organs, in the hardened and fresh state, numerous nerve - fibres may be noticed, which show more or less regu- lar varicosities, owing to local accumulations of fluid between the axis cylinder and medullary sheath. These are called varicose nerve-fibres. They occur also in the branches of the sympa- thetic nerve. The nerve-fibres of the optic and acoustic nerve are medullated, but without any neuri- lemma ; varicose fibres are common in them. 145. Medullated nerve-fibres occasionally in their course divide into two medullated fibres. Such division is very common in medullated nerve-fibres supplying striped muscular fibres, especially at or near thepointof entrance into the muscular fibres (see below). But also in other localities division of nerve-fibres may be met with. The electric nerve of the electric fishes (malapterurus, gymnotus, silurus, etc., elec-. Fig. 67.—Medullated Nerve-fibres. A, B, showing on a surface view the reticulated nature of the medullary sheath ; c, two nerve-fibres showing the axis cylinder, the medullary sheath with their vertically-arranged minute rods, and the delicate neurilemma or outer hyaline sheath. (Atlas.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Klein, E. (Edward), 1844-1925. Philadelphia : H. C. Lea's Son
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