Human anatomy, including structure and development and practical considerations . y the same posi-tion in the medulla as they do in the cord. The anterior median fissure is interrupted at the lower limit oi the medulla,for a distance of from 6-7 mm., by from five to seven robust strands of nerve-fibresthat pass obliquely acros,s the furrow, interlacing- as thcV jiroceed from the tw(j strands constitute the decussation of the pyramids ( dccussatio inramidum),whereby the s^reatcr numl)cr of the fibres of the important motor j>aths to theoi)posite sides to 1,^ain the lateral
Human anatomy, including structure and development and practical considerations . y the same posi-tion in the medulla as they do in the cord. The anterior median fissure is interrupted at the lower limit oi the medulla,for a distance of from 6-7 mm., by from five to seven robust strands of nerve-fibresthat pass obliquely acros,s the furrow, interlacing- as thcV jiroceed from the tw(j strands constitute the decussation of the pyramids ( dccussatio inramidum),whereby the s^reatcr numl)cr of the fibres of the important motor j>aths to theoi)posite sides to 1,^ain the lateral columns of the cord, in which they descend as thelateral pyramidal tracts. The fibres that remain uncrossed occupy the lateral por-tions of the [jyramids and, conxcry^in^ towards the median fissure, descend on eitherside of the latter within the anterior columns as the direct i>\ramidal tracts. The Fig. 915. Optic tractManiniillary body Pons (basilar groove) Middle cerebellar peduncU Anterior median fis^ ,— Cerebelluni- Root-bundles of ninth ..-•^^ W^. and tenth nerves. Infundibulum Cerebral peduncle Interpeduncular space :;^- Tiigeminal nerveliddle cerebellar peduncle ^Inferior cerebellar peduncle(Restiform body) Olivary eminence Arcuate fibresPyramidal decussation Root-bundles of twelfth ner\e y^ .Anterior roots of first spinal nerve Brain-stem viewed from in front, showing ventral aspect of medulla, pons and mid-brain. decussation varies in distinctness, sometimes the component strands being so buriedwithin the fissure that they are scarcely evident, or e\en not at all apparent, on thesurface and can be satisfactorily seen only when the lips of the groove are separated. Above the decussation the anterior median fissure increases in depth in conse-quence of the greater projection of the bounding pyramidal tracts. Its upper end,just below the inferior border of the pons, is marked by a slightly expanded triangulardepression, ihe/oramefi cacinn. The posterior median fis
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Keywords: ., bookauthormc, bookcentury1900, bookdecade1910, booksubjectanatomy
