Human anatomy, including structure and development and practical considerations . and, deeper,by the compressed remains ofthe floor-plate. Verj- early andbefore the flattening out of themyelencephalon has advancedto any marked extent, the de-marcation between the dorsaland ventral zones is evident asa lateral longitudinal grooveon the ventricular surface ofthe myelencephalon. Indica-tions of this division persistand in the adult medulla arerepresented by the fovea pos-terior and the sulcus lateralisseen on the floor of the fourthventricle. As in the cord-seg-ment, so in the myelencepha-lon the
Human anatomy, including structure and development and practical considerations . and, deeper,by the compressed remains ofthe floor-plate. Verj- early andbefore the flattening out of themyelencephalon has advancedto any marked extent, the de-marcation between the dorsaland ventral zones is evident asa lateral longitudinal grooveon the ventricular surface ofthe myelencephalon. Indica-tions of this division persistand in the adult medulla arerepresented by the fovea pos-terior and the sulcus lateralisseen on the floor of the fourthventricle. As in the cord-seg-ment, so in the myelencepha-lon the lateral walls are theonly regions of the neural tubein which neuroblasts are devel-oped, the roof-plate and the floor-plate containing spongioblasts alone. Very early and before the flattening out of the myelencephalon has advanced to any marked€xtent, witliin the ventral zones and close to the mid-line, appear groups of neuroblast, fromwhich axones grow ventrally to form the root-fibres of the motor (hypoglossal) nerves. Sensory Inferior colliculus Superiormedullary velum. Corpus striatum Cut wall of cerebralhemisphere Pontine flexureLateral recess Cavity of hind-brain(IV ventricle) Roof of hind-brain, lower p Reconstruction of hind-brain of human embr>-o ot about three months(50 mm.), viewed from side and behind. Drawn from His model. I I02 ANATOMY
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Keywords: ., bookauthormc, bookcentury1900, bookdecade1910, booksubjectanatomy
