. The brain as an organ of mind. 8ioelli7ig (or Mid-brain) affords the matrix fromthe upper part of which deveiojDS the Optic Lobes or CorporaQuadrigemina (fig. 122, q). From the lower part are differentiatedprolongations from the fibrous columns of the Cord and Medulla,known as the Cerebral (r). The cavity within this swell-ing gradually diminishes till in Man it persists only as a narrowpassage (6) between the cavities of the Hind and of the Fore-brain(the Fourth and Third Yeutricles) {a c). This passage is knownas the Sylvian aqueduct. The Anterior Swelling (or Fore-brain) underg
. The brain as an organ of mind. 8ioelli7ig (or Mid-brain) affords the matrix fromthe upper part of which deveiojDS the Optic Lobes or CorporaQuadrigemina (fig. 122, q). From the lower part are differentiatedprolongations from the fibrous columns of the Cord and Medulla,known as the Cerebral (r). The cavity within this swell-ing gradually diminishes till in Man it persists only as a narrowpassage (6) between the cavities of the Hind and of the Fore-brain(the Fourth and Third Yeutricles) {a c). This passage is knownas the Sylvian aqueduct. The Anterior Swelling (or Fore-brain) undergoes remarkablemodifications, principally on account of certain extraordinary out-growths to which it gives rise. From the sides of this swelling 334 DEVELOPMENT OF THE HUMAN BRAIN are developed other portions of the Cerehral Peduncles and alsothe Thalami which rest upon and grow as ganglionic thickeningsfrom the latter structures. Its diminished cavity persists as thefuture Third Ventricle {a). Its roof becomes gradually thinned. Fig. 122.—Diagrams illustrating the Progressive Changes that take place duringthe Early Stages of the Development of the Brain. (Mivart.) 1. Early condition of Brain when it consists of three hollow vesicles (a b c), thecavity of which is continuous with the wide cavity {d) of the primitive SpinalCord (»(.). 2. Here the first vesicle or Fore-brain has developed the Pineal Body ( pi) above,and the Pituitary Body ( v t) below. The wall at the anterior end of the first vesicleis the future lamina terminaUs (0- 3. This figure shows the Cerebrum {cr) budding from the first vesicle, its anteriorpart (o) being prolonged as the Olfactory Lobe ; the cavity of the Cerebrum (theincii)icnt lateral ventricle) communicating with that of the Olfactory Lo])e infront, and with that of the first Cerebral Vesicle behind (this latter cavity persistingas tlie future third ventricle ). The latter communication takes place through theforamen of Monro. The walls of the thr
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Keywords: ., bookcentury1, booksubjectbrain, booksubjectpsychologycomparative
