The development of the human body; a manual of human embryology . the ventral part of the dorsal zones the optic evagi-nations are formed, a depression, the optic recess (or),marking their point of origin. The ventral zones are but feebly developed, and formthe anterior part of the subthalamic region, while at theanterior extremity of the floor-plate an evagination oc-curs, the infundibular recess (ir), which elongates to forma funnel-shaped structure known as the hypophysis. Atits extremity the hypophysis comes in contact during thefifth week with the enlarged extremity of Rathkes pouch THE T
The development of the human body; a manual of human embryology . the ventral part of the dorsal zones the optic evagi-nations are formed, a depression, the optic recess (or),marking their point of origin. The ventral zones are but feebly developed, and formthe anterior part of the subthalamic region, while at theanterior extremity of the floor-plate an evagination oc-curs, the infundibular recess (ir), which elongates to forma funnel-shaped structure known as the hypophysis. Atits extremity the hypophysis comes in contact during thefifth week with the enlarged extremity of Rathkes pouch THE TELENCEPHALON. 419 formed by an invagination of the roof of the oral sinus(see p. 300), and applies itself closely to the posterior sur-face of this (Fig. 217) to form with it the pituitary anterior lobe at an early stage separates from themucous membrane of the oral sinus, the stalk by whichit was attached completely disappearing, and toward theend of the second month it begins to send out processesfrom its walls into the surrounding mesenchyme and so. or ir Fig. -Median Longitudinal Section op the Brain of an Em-bryo op , Anterior braehium; eg, corpus geniculatum externum; cs, corpus stria-tum; h, cerebral hemisphere; ir, infundibular recess; It, lamina term-inalis; or, optic recess; ot, optic thalamus; p, pineal process; sm, sul-cus Monroi; st, subthalamic region; to, velum interpositum.—(His.) becomes converted into a mass of solid epithelial cordsembedded in a mesenchyme rich in blood and lymphaticvessels. The cords later on divide transversely to agreater or less extent to form alveoli, the entire structurecoming to resemble somewhat the parathyreoid bodies(see p. 314), and, like these, having the function of pro-ducing an internal secretion. The posterior lobe, de-rived from the brain, retains its connection with that 420 . THE DEVELOPMENT OF THE HUMAN BODY. structure, its stalk being the infundibulum, but its ter-minal portion does not undergo
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
