. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Dominating Factor 705 vela just mentioned. Over the outside of these thinnest places in the walls of the brain extends a network of capillaries in the pia mater, the vascular meninx that intimately envelops the brain. These capillary nets are the choroid plexuses, which by invagination are pushed down into the cavities of the brain below, carrying the /S?>.-'Lamina Terminalis S2/,,i*r Interventricular Foramen jf^#Telocoele (Lateral Ventricle) S-^--D
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Dominating Factor 705 vela just mentioned. Over the outside of these thinnest places in the walls of the brain extends a network of capillaries in the pia mater, the vascular meninx that intimately envelops the brain. These capillary nets are the choroid plexuses, which by invagination are pushed down into the cavities of the brain below, carrying the /S?>.-'Lamina Terminalis S2/,,i*r Interventricular Foramen jf^#Telocoele (Lateral Ventricle) S-^--Diocoele (Third Ventricle) j-—Optic Cup J§ -Mesocoele (Aqueduct of Sylvius). Metacoele Fourth Ventricle -Myelocoele. -i—Ear Vesicle Central Canal Fig. 631. Frontal diagram to show the cavities of the brain. thin wall with them. They provide a blood supply for the inside of the brain. From the walls of the dienceph- alon, there also occur various evag- inations. In certain vertebrates these are two finger-like outpushings of the wall, one behind the other, on the dorsal side just behind the in- vaginated choroid plexus. The anterior of these evaginations, near the junction of the cerebral hemi- spheres and the diencephalon, is the parietal organ, which is particularly developed in certain reptiles, while the posterior projection, the epiphy- sis, or pineal "gland," appears in some stage of degeneration or elabora- tion in practically all vertebrates (Figs. 418 and 630). A ventral median evagination of the floor of the diencephalon, the infundibulum, has already been mentioned. It joins a glandular upgrowth from the roof of the mouth to form the hypophysis, which, like the pineal body, has been briefly considered in Chapter XVI as a gland of internal secretion (Fig. 417). The optic stalks extending out from the sides of the diencephalon in early embryonic life are also evagina- tions (Fig. 631). (d) Bendings.—In cyclostomes and other lower vertebrates the parts of
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
