. Anatomy, descriptive and applied. Anatomy. 854 THE NERVE SYSTEM side, the development of a groove or furrow, the primary arcuate fissure, which demarcates the olfactory region (^rhiiioicephalon) into a cephalic and a caudal portion. The cephalic portion develops into a blind tubular diverticulum, which grows cephalad to form the olfactory bulb and tract, its central cavity becoming obliterated (persist- ent in certain other mammals), while the caudal portion forms the roots of the olfactory nerves, the anterior perforated space or preperforatum and the subcallosal gyre. (d) At the ventral ma
. Anatomy, descriptive and applied. Anatomy. 854 THE NERVE SYSTEM side, the development of a groove or furrow, the primary arcuate fissure, which demarcates the olfactory region (^rhiiioicephalon) into a cephalic and a caudal portion. The cephalic portion develops into a blind tubular diverticulum, which grows cephalad to form the olfactory bulb and tract, its central cavity becoming obliterated (persist- ent in certain other mammals), while the caudal portion forms the roots of the olfactory nerves, the anterior perforated space or preperforatum and the subcallosal gyre. (d) At the ventral margin of the hemicerebral or secondary fore-brain vesicle an excessive proliferation of cells results in the production of several ganglionic masses—the basal ganglia, of which the largest are the lenticular nucleus (lenticula) and caudate nucleus (caudatum). (e) The median cephalic terminal wall inter- vening between the large hemicerebral vesicles persists as a thin and relatively undeveloped lamina, the lamina terminalis. (J) The remainder of the fore-brain undergoes great hypertrophy in its lateral walls to form the optic thalami, while the ventral portion develops moderately to form the hypothalamus, tuber cine- reum, posterior lobe of pituitary body, and corporffl albicantia. The dorsal wall fails to develop, and remains epithelial except at a point imme- diately adjacent to the quadrigeminal lamina of the mid-brain; here a diverticulum grows out to forin the pineal body or epiphysis (a rudi- mentary structure in man, but undoubtedly of functional use in ancestral vertebrates). (cj) The cavity of the primary fore-brain vesicle ode of undergoes alterations in form as the secondary. \) Fig. 624.—Plan showing the m iaTtt°cenlli''earaf ofthetin-5 cSrS! metamorphoscs of its walls procccd in the course c;'lS'e?ere^pt\on.''-fl^^ of development. The hollow cerebral buds so E. Myeiencephaion. F. Central canal of rapidly outstrip all Other parts of thc braiu that cord. G. Later
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1913
