Human anatomy, including structure and development and practical considerations . li from thetracts of GoU and of Burdach become inxaded by new masses of gray matter, thenucleus gracilis and cuneatus. The graciie nucleus, the first encountered, begins as a narrow area of grayFk;. 921. matter within the correspond- ing strand, on a level withthe pyramidal decussation(Fig. 921). It rapidly in-creases in bulk, until itnot only invades the entirefuniculus gracilis, but alsojoins the gray matter sur-rounding the central superficial stratum ofspinal fibres gradually dimin-ishes as more and
Human anatomy, including structure and development and practical considerations . li from thetracts of GoU and of Burdach become inxaded by new masses of gray matter, thenucleus gracilis and cuneatus. The graciie nucleus, the first encountered, begins as a narrow area of grayFk;. 921. matter within the correspond- ing strand, on a level withthe pyramidal decussation(Fig. 921). It rapidly in-creases in bulk, until itnot only invades the entirefuniculus gracilis, but alsojoins the gray matter sur-rounding the central superficial stratum ofspinal fibres gradually dimin-ishes as more and more of itscomponents end around thecells of the graciie nucleus,until, finally, all are inter-rupted. Meanwhile thecuneate nucleus appearswithin the funiculus cuneatusas a dorsally directed club-shaped mass of gray mat-ter (Fig. 922) which soonbecomes a prominent mottled area, sharply defined by the o\erlying stratum ofBurdach fibres. The cuneate nucleus extends to a higher level than the nucleus Nucleus gracilis Funiculuscuneatus Spinalroot of VnerveSubstantia3^1 gelatinosa. Pyramidal Transverse section of medulla at level B, Fig. 919; pyramidal decus-sation well established; posterior cornua are displaced laterally byposterior columns. -5^. Preparation by Professor Spiller. 1070 111 MAN ANATONn. gracilis ami, c\xii after the disapiK-arancc of the latter, contiiuies as a strikiiij^ collec-tion of gray matter beneath the tlorsal surface of the medulla, from which it isseparatetl by the posterior superficial arcuate fibres. Within the upper part of thefasciculus cuneatus the gray matter becomes subdivided into two masses (Iig. 924),the more superficial and C(jntinuous of which is called the nucleus luucalus cxtcrnus,and the deeper and more broken one, the nuclius cuneatus inlernns. Owing to the increased bulk of the fasciculi of the posterior area occasioned by theai)pearance and expansion of the contained nuclei, the dorsal horns of the gray matterare displaced
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Keywords: ., bookauthormc, bookcentury1900, bookdecade1910, booksubjectanatomy
