Quain's elements of anatomy . s of the brain. They then form large hollowbodies with comparatively thru walls superiorly, the lateral ventricles being greatly Fig. 739.—^VlEW OF THE INNER Fig. 739. SURFACE OP THE RIGHT HALFOP THE FCETAL BRAIN OP ABOUT SIX MONTHS. (From Reichert.) F, frontal lobe ; P, parietal ;0, occipital ; T, temporal ; I,olfactory bulb; II, right opticnerve; fp, calloso-marginal fis-sure ; p, external ; p, internalparts of the parieto-occipital fis-sure; h, calcarine fissure ; g, gyrusfornicatus; c, c, corpus callosum ;??, septum lucidum ; /, placedbetween the middle commis
Quain's elements of anatomy . s of the brain. They then form large hollowbodies with comparatively thru walls superiorly, the lateral ventricles being greatly Fig. 739.—^VlEW OF THE INNER Fig. 739. SURFACE OP THE RIGHT HALFOP THE FCETAL BRAIN OP ABOUT SIX MONTHS. (From Reichert.) F, frontal lobe ; P, parietal ;0, occipital ; T, temporal ; I,olfactory bulb; II, right opticnerve; fp, calloso-marginal fis-sure ; p, external ; p, internalparts of the parieto-occipital fis-sure; h, calcarine fissure ; g, gyrusfornicatus; c, c, corpus callosum ;??, septum lucidum ; /, placedbetween the middle commissureand the foramen of Monro ;V, in the upper part of thethird ventricle immediately be-low the velum interpositum andfornix ; v, in the back part of the third ventricle below the pineal gland, and pointing by a line to the aqueduct ofSylvius ; v, in the lower part of the third ventricle above the infundibulum ; r, recessuspinealis passing backwards from the tela choroidea ; 2^^, pons Yarolii; Ce, cerebellum. VOL. II. 3 H. 834 THE NERVOUS SYSTEM. dilated, and communipating by a wide aiDerture with each other, and with thethird ventricle, by the foramen of Monro. The growth of the hemispheres takesplace progressively from before backwards, so that they come to cover in succes-sion the thalami, corjDora quadrigemina and cerebellnm, which all originally stoodin a series behind them, as they do permanently in the lowest vertebrates. Bythe end of the third month the hemispheres have extended so far backwards asto cover the thalami; at the fourth they reach the corpora quadrigemina ; at thesixth they cover those bodies and great part of the cerebellum, beyond whichthey project still further backwards by the end of the seventh month. The floor especially of the hemispheres thickens considerably, and the corpusstriatum increasing greatly in magnitude, at the same time projects upwards intothe lateral ventricles so as to give these cavities an arched form and mark outtheir anterior an
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