If we regard it as an exercise of the sense of touch, in what is at the time the main touch organ, we have an activity closely parallel with the constant interest in the use of sight in the early months. Observers have been misled by failing to realize that the mouth, not the hand, is the primitive touch organ. The baby behaves with the things in his mouth as if he was interested in feeling them, not in eating them. He does not try to swallow them (though he may be depended on to do it without trying, if they are small), but licks, sucks, mumbles them about, and in every way gets the utmost touch sensation out of them. Preyer saw a look of pleasure caused by sucking a pencil, before the baby had ever tasted food, when he could not have had the least taste association with the feeling. There is plenty of evidence that the act of sucking (the muscular sensation as well as that of touch) is in itself highly agreeable to babies. I have spoken of the great and active interest, at this time, in studying the visible world. By the end of the fourth month the baby had certainly learned the look of many things, and was well aware when it was in any way changed. In a strange room she would renew the eager and surprised staring about which had nearly ceased in familiar rooms; and if one of us appeared in a bonnet she would look with curiosity and interest at our changed aspect. She doubtless knew us all apart by this time, though she gave no clear evidence of it, except in the case of grandpa, whom she often greeted with cries of joy and flying hands. From the middle of the fourth month she followed us constantly with her eyes as we moved about. Her eyes were thus drawn to greater distances, and her range of vision increased; before this she had hardly noticed anything across the room. In the latter part of the month she looked with especial curiosity at people’s faces on the other side of the room, and I guessed that it was because they looked so much smaller to her--as they would to us if we had not learned to allow for the distance. A face fifteen feet away can be completely hidden by a fifty cent piece held out at arm’s length; our friends shrink to small dolls in our eyes every time they cross the room, but we bring them up to their real size by trained imagination. The baby, who had not yet the trained imagination, must have seen strange shrinkings and swellings as people moved from her or toward her, and as she was carried about the room.