Many other things will the brained frog do--almost enough to convince a superficial observer that the cerebral hemispheres are a luxurious superfluity to the physical and mental well-being of the average inhabitant of the swamp. But no. A little watching shows that for this seemingly intelligent creature past, present and future are alike blotted out. Let the frog alone and it sits motionless, buried not in the profundity of its thoughts, but in the abyss of its thoughtlessness. In the midst of abundance it starves--not, like Tantalus, because it cannot gratify its desires, but because it has no desires to gratify. It feels no hunger, or if it feels hunger seeks no food. A perfect automaton, it moves when touched, it croaks when stroked, it answers to a multitude of external irritations, but when untouched and left to itself it is as a lifeless clod until the sun dries it up and the winds blow it away.
The fish whose cerebral hemispheres or upper brain has been taken away has, like the frog, all conscious perception blotted out, but, unlike the frog, it is in perpetual motion. Stopping not for food, it rushes through the water, avoiding obstacles, but never ceasing its mad race until muscle-power or nerve-force fails because of excessive use and lack of nourishment.
The cerebral hemispheres can also readily be removed from birds. The pigeon so mutilated presents phenomena similar to those offered by the frog. He remains perfectly quiet, balancing himself readily on his perch, but with drooping eyes and sunken head, motionless so long as undisturbed. Move his perch, and he struggles to maintain equilibrium; fire a pistol near him, and he starts, only to fall back at once into his apathy; approach him in the dark with a bright light, and he gazes at the candle with a fixed stare, and sometimes follows its movements with his head; strike at him from the front, and he will draw back; pinch his toes, and he moves. It is therefore plain that he in a certain sense sees, hears and feels. Yet when perishing with hunger he never pecks at the corn which he sees placed before him, and if left alone dies. If, however, the food be placed in his mouth he swallows it eagerly, and by care can be kept alive for an indefinite period.