Page:Popular Science Monthly Volume 1.djvu/356

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344
THE POPULAR SCIENCE MONTHLY.
NERVOUS CONTROL OF ANIMAL MOVEMENTS.
FROM THE FRENCH OF M. ONIMUS.[1]

SINCE the celebrated experiments of Flourens, we know for certain that all the acts of the vegetative life in animals are completely independent of the cerebral lobes, and that an animal deprived of these continues to live as well as before, with only this difference, that it loses all will and instinct. With superior as well as inferior animals the cutting away of the cerebral lobes does not put an end to the movements which were possible before; only these movements take on particular characters. In the first place, they are more regular, and may be regarded as the true normal type, for mental influences do not modify them. The locomotive apparatus acts without restraint, and we may, therefore, say that the movements are more normal than in the normal state. In the second place, when the cerebrum is removed the movements only commence after excitations; they cannot start themselves. The frog must be put in the water to swim, and the pigeon thrown in the air to fly. In animals without a cerebrum the physiologist can determine such or such an act, limit it, arrest it; he can foresee movements, and tell in advance what will take place in such conditions, as absolutely as the chemist knows in advance the reactions he will get on mixing certain bodies.

Another peculiarity of movements that take place when the cerebral lobes are removed is, their continuation when once commenced. On the earth a frog without a cerebrum, when irritated, makes two, three, or more leaps; he rarely stops with one. Placed in the water he continues to swim till he encounters an obstacle. The pigeon continues to fly, the duck and the goose to swim. The striking thing about it is, the continuation of the state determined at first by an impulse from without; and we cannot help associating these facts, about animals deprived of their cerebral lobes, with the characteristic properties of inorganic matter. Put agoing, the animal without a cerebrum continues to move till the exhaustion of the conditions of movement, or till it encounters resistance. Put in repose, it remains inert till some exterior cause sets it in motion. It is inert living matter.

The phenomena we are about to consider are caused either by im-

  1. The importance of understanding the springs of animal movement and the conditions of their control is the reason for including the present article in The Popular Science Monthly. It has been translated and abridged, from the Revue Scientifique, for the general reader, but those who wish for more detail in the presentation are referred to Dr. Hammond's Quarterly Journal of Psychological Medicine, for July, where the discussion will be given complete, and where kindred questions are elaborately discussed. Fig. 1 has been inserted to give a general notion of the parts of the brain referred to in the article.—Ed.