. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. AVES. 299. are equally obvious in the brains of reptiles. They are, however, differently disposed in birds ; the optic lobes, which in reptiles intervene and are visible between the cerebrum and cerebel- lum, being in birds displaced, as it were, by the hemisphere and cerebellum coming into close contact, so that the optic lobes are pushed downwards and to one side. The transverse convolutions of the cerebellum at once distin- guish, however, the brain of a bird from that of any reptile and most fishes; but it is a curi-
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. AVES. 299. are equally obvious in the brains of reptiles. They are, however, differently disposed in birds ; the optic lobes, which in reptiles intervene and are visible between the cerebrum and cerebel- lum, being in birds displaced, as it were, by the hemisphere and cerebellum coming into close contact, so that the optic lobes are pushed downwards and to one side. The transverse convolutions of the cerebellum at once distin- guish, however, the brain of a bird from that of any reptile and most fishes; but it is a curi- ous fact that the cerebellum in the sharks is similarly composed of a vermiform process only, transversely folded or convoluted. The cerebral hemispheres sometimes present the form of a flattened oval, as in the Parrot tribe, but in general are of a convex cordiform shape, with the apex directed forward. Fig. 135. The optic lobes (b, jig. \ 35) are rounded tubercles, situated be- low and behind the hemispheres, in the la- teral interspace between these and the cerebel- lum. The cerebellum is ,. ., • f composed of the middle Base of the brain of a . v . , . ,. Pigeon. *°"e onty> anc* ls °* a compressed arched form. The medulla oblongata presents neither a tuber annulare nor corpora olivaria or pyrami- dalia, but is a large uniform tract situated be- tween and behind the optic lobes. On the lower part of the side of each cere- bral hemisphere there is a depression which corresponds to the fissura magna Sylvii, and is the only appearance which the hemispheres present of a division into lobes. Elsewhere there are no traces of convolutions, the cere- brum in this respect resembling that of Rep- tiles and Fishes, and some of the least intel- ligent orders of Mammalia, as the Rodentia} Marsupiiita, and Edentata. The optic lobes are also devoid of the transverse fissure which bisects the optic lobes of mammalia. The cerebellum is marked by close and transverse anfractuosi
Size: 1631px × 1532px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, booksubjectanatomy, booksubjectphysiology, booksubjectzoology
