. A text-book of human physiology . s)Midbrain (optic lobes) Hindbrain(cerebellum) Afterbrain(medullaoblongata) Fig. 274.—The brain of Squaliuscephalus, a bony fish, after Steiner. FUNCTIONS OF THE BRAIX-STEM AS A WHOLE 619 In the true fishes the cerebrum is but slightly developed, and in the lampreysand bony fishes the cortex consists of only a simple layer of epithelial cells. After extirpation of the cerebrum from a bony fish (Squalius cephalus, ) the animal moves exactly like a noiTQal animal, and, according to Steiner,it is quite impossible to discover anything anomalous in its mov
. A text-book of human physiology . s)Midbrain (optic lobes) Hindbrain(cerebellum) Afterbrain(medullaoblongata) Fig. 274.—The brain of Squaliuscephalus, a bony fish, after Steiner. FUNCTIONS OF THE BRAIX-STEM AS A WHOLE 619 In the true fishes the cerebrum is but slightly developed, and in the lampreysand bony fishes the cortex consists of only a simple layer of epithelial cells. After extirpation of the cerebrum from a bony fish (Squalius cephalus, ) the animal moves exactly like a noiTQal animal, and, according to Steiner,it is quite impossible to discover anything anomalous in its movements. Whenan earthworm is thrown to the fish, it makes a rush for the booty, seizes it whileit is still falling and devours it. A cord of about the same dimensions throwninto the water may or may not be seized, but is never eaten. A decerebratedfish may be even fastidious about its food; spurning fish worms but takingcrumbs of bread from the surface of the water. When one red wafer and fourwhite ones are thrown to it, the ^^^ _. Nasal capsules Olfactory bulb Forebrain (hemispheres)Tweenbrain Midbrain(optic lobes) Hindbrain(cerebellum) Afterbrain I medulla oblongata)Vagus nerve Fig. 275.—The brain of Scyllium canicula, a dog-shark, after Steiner. fish regularly chooses first the redand then the white ones. It doesnot move to take the food from theobservers hand, but will take itfrom a long string. Finally, thedecerebrated fish wall exchange ca-resses with its uninjured compan-ions. From these observations wemay conclude that suppressipn ofthe cerebrum in this genus is ofno particular consequence—that tojudge from the behavior of theanimal after the operation, theparts remaining are suflficient forthe discharge of all the centralfunctions. We have no experiments whichgive us any clew as to the impor-tance of the tweenbrain in the bony fish. But Steiner has reported some in whichhe removed both the midbrain and the tweenbrain along with the this operatio
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