. Elementary anatomy and physiology : for colleges, academies, and other schools . Fig. 332. tiles constitutes but a very small part of the body. In the frog the proportion to the whole weight of the body is as 1: 172; in the Coluber matrix (snake), 1 : 792 ; in a turtle, 1 : 5688. The hemi- spheres are smooth and hollow internally. The optic lobes are large in proportion to the size of the eyes, and are hol- low internally. The cerebel- lum of frogs is merely a thin plate of nervous matter. 665. Nervous System of Fishes—We find the lowest development of the nervous system among vertebrates in
. Elementary anatomy and physiology : for colleges, academies, and other schools . Fig. 332. tiles constitutes but a very small part of the body. In the frog the proportion to the whole weight of the body is as 1: 172; in the Coluber matrix (snake), 1 : 792 ; in a turtle, 1 : 5688. The hemi- spheres are smooth and hollow internally. The optic lobes are large in proportion to the size of the eyes, and are hol- low internally. The cerebel- lum of frogs is merely a thin plate of nervous matter. 665. Nervous System of Fishes—We find the lowest development of the nervous system among vertebrates in the fishes. The brain here does not fill the whole cranial cavity, so that between the brain and dura mater there is found a quantity of loose cellular tissue, with wThich is inter- spersed a fluid oil. The brain in weight does not equal that of the spinal cord, nor is it but a little broader than the cord. Its weight in proportion to that of the body is about Tj\ tth part. It is composed of eight lobes, partly in pairs, and partly unpaired behind one another, which seem to correspond to the cerebellum (divided), corpora quadrigemina, thalami optici, and medulla oblongata. 666. Electrical Organs in Fishes.—There are at least seven species of fish that possess the power of giving electric discharges. The organs which accomplish this in the Torpedo are two large crescent-like bodies (see Fig. 334), which are Brain of Turtle. A, Olfactive Ganglia. B, Cerebrum. C, Optic Ganglia. D, Cere- bellum. 664. What is said of the brain of reptiles? State, its comparative size with that of the whole body. 665. State some of the peculiarities of the brain in fishes. What is its relative weight? 666. What is said of the electrical organs of some fishes? Give the anatomy of these organs.
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