Page:Popular Science Monthly Volume 33.djvu/261

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boring areas, species lost its significance as a term of fixed meaning, and can not be separated from genus on one side and subspecies or variety on the other.

Though the examples made use of in this discussion are taken from the vertebrate type of animals, the other great divisions fall under the same law, each in its own way, and under limitations set by the characters of the types themselves.

By Prof. W. PREYER.

TO determine as exactly as possible the date of the first imitative acts is of especial interest in regard to the genesis of mind, because even the most insignificant imitative movement furnishes a sure proof of activity of the cerebrum. For, in order to imitate, one must first perceive through the senses; secondly, have an idea of what has been perceived; thirdly, execute a movement corresponding to this idea. Now, this threefold central process can not exist without a cerebrum, or without certain parts of the cerebrum, probably the cortical substance. Without the cerebral cortex, certain perceptions are possible, to be sure; many movements are possible, but not the generation of the latter out of the former. However often imitation has the appearance of an involuntary movement, yet when it was executed the first time, it must have been executed with intention—i. e., voluntarily. When a child imitates, it has already a will. But the oftener a voluntary movement is repeated, always in the same way, so much more it approximates reflex movement. Hence many imitative acts, even in the child, occur involuntarily quite early. But the first ones are willed. When do they make their appearance?

If we make, for the infant to see, a movement that he has often practiced of his own accord, he can make a successful imitation much earlier than is commonly supposed. Such a movement, which I employed as suitable for early imitation, is the pursing of the mouth, the protruding of the closed lips, which often occurs (even in adults), along with a great strain of the attention. ~

This protruding of the lips occurred with my child on the

  1. From "The Mind of the Child: Part I. The Senses and the Will." Being observations concerning the mental development of the human being in the first year of life. By W. Preyer, Professor of Physiology in the University of Jena. Translated from the German by II. W. Brown, with an Introduction by G. Stanley Hall. New York: D. Appleton & Co., 1888.