. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CETACEA. 583 spinal chord (a, J?g. 272) gently expanding into the medulla ohlongata, on the anterior surface of which the corpora pyramidalia (b, Jig. 272) are seen well defined and prominent. At the point where they begin to rise above the surface of the medulla, there is a manifest decussation of their internal fibres; they pro- ceed through the pans Varoli (c), and are continued into the crura cerebri. The corpora ollvuria are situated near the pyramidalia; they do not, however, project from the surface as in the huma
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. CETACEA. 583 spinal chord (a, J?g. 272) gently expanding into the medulla ohlongata, on the anterior surface of which the corpora pyramidalia (b, Jig. 272) are seen well defined and prominent. At the point where they begin to rise above the surface of the medulla, there is a manifest decussation of their internal fibres; they pro- ceed through the pans Varoli (c), and are continued into the crura cerebri. The corpora ollvuria are situated near the pyramidalia; they do not, however, project from the surface as in the human brain, but are distinguishable by the internal grey sub- stance (corpus dentatum alivx). Their medul- lary fibres proceed through the pons and enter the bigeminal bodies, in which they converge and decussate each other. The transverse medullary fibres, which are seen in most Mammalia extending across the under surface of the medulla oblongata imme- diately behind the pons, and which Treviranus has called the trapezium, are wanting in the brain of the Dolphin, as in that of the Orang Utan and the Human subject. The two posterior columns of the spinal chord are continued (according to Tiedemann) as the corpora restiformia to the cerebellum. Between these is situated the fourth ventricle, from the floor of which the acoustic nerves take their origin. The very large size of the cerebellum in proportion to the spinal chord and cerebrum, which Hunter noticed in the Piked Whale, is equally remarkable in the Dolphin. The cere- bellum is deeply divided into lobes, of which six may be distinguished on the upper surface of each hemisphere. Of these, two small lobes correspond to the posterior superior lobes of the human cerebellum. On the under surface we remark the posterior inferior lobes (e), the anterior inferior lobes (fj, one lobe corresponding to the amygdaloid lobe of Reil (g), and the floccus (ti). Each lobe is subdivided by deep fissures into smaller lobes, and these again by
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