A system of obstetrics . lining the vesicles give rise to the ependyma of the ventri-cles, to the white and gray matter of the brain, and to its investing mesoblast gives origin to the blood-vessels, the pia mater,the choroid plexuses, and so forth. In some parts the epiblastic wallsof the primary cavities thicken greatly; in others they remain thin,even forming throughout life a mere single layer of cells, as on theroof of the fourth ventricle of the adult brain. The cerebral vesicles (prosencephalon) give rise by the thickening oftheir roofs and outer sides to the cerebral hemi
A system of obstetrics . lining the vesicles give rise to the ependyma of the ventri-cles, to the white and gray matter of the brain, and to its investing mesoblast gives origin to the blood-vessels, the pia mater,the choroid plexuses, and so forth. In some parts the epiblastic wallsof the primary cavities thicken greatly; in others they remain thin,even forming throughout life a mere single layer of cells, as on theroof of the fourth ventricle of the adult brain. The cerebral vesicles (prosencephalon) give rise by the thickening oftheir roofs and outer sides to the cerebral hemispheres. Their innersides for a considerable area remain very thin, and, coming nearly incontact in the middle line, leave a space between them which is laterclosed in above by the corpus callosum and below by the fornix; thespace thus enclosed is the fifth ventricle of the mammalian brain, whichdiffers from all the others in not being a remnant of the original cavityof the medullary canal. 158 DEVELOPMENT OF THE The multiplication and modification of the epiblast cells forming thefloor of the primary cerebral vesicle give rise to the corpus striatum. The primitive fore-brain, afterit has budded off the optic andcerebral vesicles, is named thediencephalon or inter-brain. Itdevelops on its dorsal surface thepineal process and gland;1 itssides form the optic thalami andpart of the cerebral peduncles;its floor gives origin to the infun-dibulum,2 part of the crura cer-ebri, tuber cinereum, and opticchiasma; its cavity remains as thethird ventricle. The anterior commissure in am-phibia and reptiles is a complexstructure, consisting of an upperportion developed from the cere-bral vesicles, and representing arudimentary corpus callosum, and Diagram representing the Brain at an early stage i norriofi the trup qntprinr of development: I, cavity of primary fore-brain: a 10W®! Pr-ltlOU, tlie tiue ailteiior the thickened epiblast, th. on its sides will be- commissure, developed f
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectobstetrics, bookyear1
