. A treatise on nervous and mental diseases, for students and practitioners of medicine. lly—lies a DISEASES OF THE PERIPHEHAL NERVES. 175 finely granulated mass, containing two kinds of nuclei, the smallerones being granulated and of irregular shape, the larger ones beingoval with double contours and a nucleolus. The former are knownas the Scheiden- or Gedstkerne, or, as Ranvier calls them, the noyauxvaginaux or noyaux de Iarboration, while the latter are the Grundor 8ohlenkerne, or noyaux fondamentaux of Ranvier. To this motorend-plate, lyiug upon the muscle, come the medullated nerve fibres
. A treatise on nervous and mental diseases, for students and practitioners of medicine. lly—lies a DISEASES OF THE PERIPHEHAL NERVES. 175 finely granulated mass, containing two kinds of nuclei, the smallerones being granulated and of irregular shape, the larger ones beingoval with double contours and a nucleolus. The former are knownas the Scheiden- or Gedstkerne, or, as Ranvier calls them, the noyauxvaginaux or noyaux de Iarboration, while the latter are the Grundor 8ohlenkerne, or noyaux fondamentaux of Ranvier. To this motorend-plate, lyiug upon the muscle, come the medullated nerve fibres bya right angle, losing their medullary sheath as they pass into the nerveplexus just described. The sensory nerve, on the other hand, takesits origin in the gangliou upon the posterior root, and passes downto the sensory structures of the periphery to Pacinian corpuscles,the tactile bodies, the end-bulbs, and the neive networks (page 66).From its point of origin to its peripheral termination there is onestructure of the nerve that runs continuously, the axis-cylinder, as Fig. lOi. Drawing of normal sciatic nerve of frog. Obtained by teasing. has already been said. This is a highly nitrogenized body con-sisting of a number of primitive fibrils arranged longitudinallyand glued together by a minutely granular substance. Around thisaxis-cylinder is a sheath of myelin, a fatty substance which doesnot pass with the nerve into either the central or peripheral end-organs, and which, moreover, is not continuous in its course, butconsists of a series of tubes or segments whose points of junctionare marked by a constriction in the contour. Finally, around the axis-cylinder and the sheaths of myelin is a connective tissue covering thesheath of Schwann, and this is also segmented, the point of constric-tion being known as the node of Ranvier. Occasionally, upon theaxis-cylinder are seen certain lines which are known as arrow-mark-ings, or markings of Schmitt. These were formerly thought
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