. A manual of diseases of the nervous system. due to the division of the latter (Sherrington); but such divisionhas not been actually demonstrated, and is probably not variation in size is from 1 to 25 /u (a-rg-oo ^^ t-qVo inch). Thevariations are especially great in the fibres of the pyramidal tract, * So that in some descriptions the posterior horn is divided into (1) spongy sub-stance of the horn itself; (2) gelatinous zone of the caput, and (3) spongy zoneat the tip of the horn. See Lissauer, * Arch, f. Psych., 1886. t See Obersteiner, loc. cit., p. 192. STRUOTUEE. 171 and it
. A manual of diseases of the nervous system. due to the division of the latter (Sherrington); but such divisionhas not been actually demonstrated, and is probably not variation in size is from 1 to 25 /u (a-rg-oo ^^ t-qVo inch). Thevariations are especially great in the fibres of the pyramidal tract, * So that in some descriptions the posterior horn is divided into (1) spongy sub-stance of the horn itself; (2) gelatinous zone of the caput, and (3) spongy zoneat the tip of the horn. See Lissauer, * Arch, f. Psych., 1886. t See Obersteiner, loc. cit., p. 192. STRUOTUEE. 171 and it is in these that division has been thought to occur. Those ofthe direct cerebellar tract are uniformly large, while most of thosethat constitute the postero-median column are small. It will facilitate the detailed study of the tracts if we considerfirst those that undergo secondary degeneiation for a considerabledistance, as our knowledge regarding these is the most degenerations are both ascending and descending. Only one Fia. 70.—Diagram of the elements of the white substance at various levels):M. ^^ ^^^^ spinal cord. (Modified from Flechsig.) The pyramidal tracts are shaded by short horizontal lines; the direct cerebellar tract by dots; the posterior median column by dots, as it degenerates in disease of the lowest £part of the cord or of the nerves of the cauda equina; the small circles ? in the forepart of this column indicate the area which degenerates in ^disease of the cervical enlargement. The antero-lateral ascending tract is shown by crosses. It is not represented in the first cervical section because there are no facts, at present, to show its exact position here; it probably lies chiefly in front of, and between, the direct cerebellar and pyramidal tracts, as c. 3. The anterior ground-fibres, lateral limiting layer, and postero-external column are left white. Fig. 62 should be compared with this. 172 SPINAL OOED. important set of fibres degen
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnervoussystem, bookye
