the muscles can contract in such a way that the movement will be directed; there is a coordination of the muscular movements. I should like to read to you just these three or four lines from Miss Shinn, who has given perhaps the best story of the development of a baby which has yet been written. This is not merely my opinion, but also the opinion of my psychological colleagues at Cambridge whom I consulted before venturing to express the idea before you, and I find that they take the view that Miss Shinn's book, which is charmingly written, is really done with such precision and understanding of the psychological problems involved that it may fairly be called the best of the books treating of the mental development of a baby. Miss Shinn says, referring to the condition of the child at the end of two months—"Such is the mere life of vegetation the baby lived during the first two months; no grown person ever experienced such an expansion of life—such a progress from power to power in that length of time." She is not thinking of senescence, as we have been thinking of it, but she makes precisely the assertion, which seems to me to be true, that the baby in two months has accomplished an amount of development which no adult is capable of. And now at three months we find another great discovery is made by the baby, that it is possible to bring the sensations which it receives into combination with the movements which it makes. It learns to coordinate its sensory impressions and its motor responses. We hardly realize what a great rôle this adjustment, between what our muscles can do and what our senses tell us, plays in our daily life. It is the fundamental thing in all our daily actions, and though by habit we perform it almost unconsciously, it is a thing most difficult to learn. Yet the baby has acquired the art, though he only gradually gets to be perfect in it. Again we see, at the end of the fourth month, that the baby begins to show some idea of another great principle—the idea that it can do something. It shows evidence of having purpose in what it does. Its movements are no longer purely accidental. At four months we find yet another equally astonishing addition to the achievements of this marvelous baby. He makes the amazing discovery that the two sides of an object are not separate things, but are parts of the same. When a face, for instance, disappears by a person's turning around, that face, to a baby of one month, probably simply vanishes, ceases to exist: but the baby at four months realizes that the face and the back of the head belong to the same object. He has acquired the idea of objects existing in the world around him. That is an enormous achievement, for this little baby has no instructor; he is finding out these things by his own unaided efforts. Then at five months begins the age of handling, when the baby feels of everything. It feels urgently of all the objects which it can get hold of and perhaps most of all of its own body. It is finding that it can touch its various parts and that when its hands and parts of its own body come in contact it has the double
