. The chordates. Chordata. A. Sauropsida: Class Aves B. „„ ffff 535. Fig. 416. Brain of pigeon. (A) Dorsal view. (B) Lateral view. (Hyp) Hypophy- sis; (Jnf) infundibulum; (L. ol.) olfactory lobes; (HH) cerebellum; (Med) spinal cord (medulla spinalis); (MH) optic lobes; (NH) medulla oblongata; (Tr. opt) optic tract; (VH) cerebral hemispheres; (I-XII) cranial nerves; (1, 2) first and second spinal nerves. (Courtesy, Wiedersheim: "Grundriss der vergleichenden Anatomie der Wirbeltiere," Jena, Gustav Fischer.) more fibers in the optic nerve and the greater the number of nervous elements i
. The chordates. Chordata. A. Sauropsida: Class Aves B. „„ ffff 535. Fig. 416. Brain of pigeon. (A) Dorsal view. (B) Lateral view. (Hyp) Hypophy- sis; (Jnf) infundibulum; (L. ol.) olfactory lobes; (HH) cerebellum; (Med) spinal cord (medulla spinalis); (MH) optic lobes; (NH) medulla oblongata; (Tr. opt) optic tract; (VH) cerebral hemispheres; (I-XII) cranial nerves; (1, 2) first and second spinal nerves. (Courtesy, Wiedersheim: "Grundriss der vergleichenden Anatomie der Wirbeltiere," Jena, Gustav Fischer.) more fibers in the optic nerve and the greater the number of nervous elements in the optic centers of the brain. The extraordinarily large eyes of the bird are associated with large optic lobes. The all-important function of the cerebellum is the coordination of the activities of the complex sets of muscles involved in locomotion and in maintaining bodily equilibrium—balancing, posture. This co- ordination depends upon stimuli received by the various sense-organs, especially important being those received by the eyes and by the equilibratory organs (semicircular canals) of the ears. Each type of sensory organ has its corresponding primary sensory center in the brain —smell in the forebrain; sight in the midbrain (optic lobes); equilib- rium and hearing, taste, and the various integumentary senses in the hindbrain. Therefore, from these several primary sensory centers, nervous impulses must be relayed into the cerebellum along connecting tracts of nerve-fibers. The muscular activities concerned in flight are of a peculiarly complex sort and require, for their precise coordination, a correspondingly complex nervous mechanism. The cerebellum, how- ever, merely coordinates these activities. Whether or not flight shall occur, its direction and speed, and, in short, the whole pattern of the animal's activities, are determined within nervous centers situated elsewhere in the brain and, for the most part, in regions anterior to the. Please note that these
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