. An introduction to zoology : for the use of high schools . halon and the 0[)tic lobes, whichare entirely hidden by the backward extension of the cerebralhemispheres. The cerebellum also has gained in size, especiallyits latei-al loV)es, which are joined by a series of fibres crossingtransvei-sely under the fore part of the hind brain, and consti-tuting the pons Varolii. In front of the pons, the fibres whichascend through the medvilla oblongata towards the cerebrumdiverge in two masses, the crura, to the hemispheres, and infront of the crura is the only part of the thalamic region whichi-eac
. An introduction to zoology : for the use of high schools . halon and the 0[)tic lobes, whichare entirely hidden by the backward extension of the cerebralhemispheres. The cerebellum also has gained in size, especiallyits latei-al loV)es, which are joined by a series of fibres crossingtransvei-sely under the fore part of the hind brain, and consti-tuting the pons Varolii. In front of the pons, the fibres whichascend through the medvilla oblongata towards the cerebrumdiverge in two masses, the crura, to the hemispheres, and infront of the crura is the only part of the thalamic region whichi-eaches the surface of the brain, viz. the hypophysis and in-fundibulum. On the whole, the most important changes arethose which have taken place in the cerebrum, for not only has itincreased in size by growing forward, backward and towards thesides, but the grey matter of its surface, instead of being smooth,is folded inwards in such a way as to leave a series of fissures onthe surface of the cerebrum with intervening convolutions. We 152 HIGH SCHOOL have already seen in the cerebelhim of the bird a similar ]ilanfor accommodating a large surface of grey matter in a compara-tively small space, and the cats cerebellum also exhibits thecharacteristic arbor vitsQ arrangement. The cerebral hemi-spheres are not inde-pendent of each other,^,y^_^v» ;^^^^^__,—.^W^^^iJ-;^ for, apart from certain -Cir transverse bundles offibres present in thelower classes, there isalso formed between,. J. , .^ J- , ^- c^ ? t , those parts of the hemi- Fijr. 103.—Median lon^tudinal section of brain of cat i . (Modified after Wilder.) Sphei^CS wlucll project .9 Spinal cord with contained central canal mo me- j^^ck OVer the true rOofdiiUa oblon^ata ; p, pons varolii ; cb, cerebellum, form-in ir the floor and roof of the 4tii ventricle //i^.^ optic ^f the brain (Fig, 103)lobes or ooiTJoraquadrigemina, the roof of the mesocoDle \ o / or iter, the floor is formed by the crura in front of the j^^-^
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1889
