Characteristics of the Healthy Infant.—­ The average weight of an infant at birth is about seven pounds, and its length is about twenty inches; the extremes are four pounds or a little less up to eleven pounds.  The head and trunk of the child are developed out of proportion to the limbs.

The skin of the new-born infant varies from pinkish to red; about the fourth day the color becomes somewhat yellowish; this tinge should disappear about the end of the second week, and at the same time the skin begins to peel off.This process lasts about two weeks longer, when the baby’s skin takes on its normal color.

The shape of the head varies greatly, much being due to the amount of pressure during labor; but this disappears in a few days.  As a rule, the large bones of the head are felt to be separated by membranous ridges called sutures; there is one on the median line on the top of the head, and at either end of the suture is a large open space, called a fontanel.  The largest one is at the front of the head, and is called the anterior fontanel; it is about large enough to be covered by the tips of two fingers, and is of a lozenge shape; this opening does not close till the child is about eighteen months old.  In a healthy baby this fontanel should be on a level with the bones of the head; a slight pulsation may be noticed in it, due to the pulsations of the vessels of the brain.  There is a much smaller three-cornered fontanel at the back of the suture, and one behind either ear; these soon close up with bone.

A new-born baby cannot probably do any more than distinguish light from darkness.  Up to the sixth week there is an inability at coordination of the ocular muscles; after this time the eyes begin to move in an orderly manner, and they will follow a bright object moved slowly in front of them.  At about the end of the second month rapid movements are perceived, as is evinced by the child’s closing its eyes quickly on an object suddenly approaching it.  At three months the child begins to recognize colors; the first recognized are yellow, red, pure white, gray, and black.  But the faculty of distinguishing between colors is not perfected till the third year.  The mother is recognized about the third month.  Hearing and a sense of smell develop rapidly after birth; loud noises in its vicinity will cause a child to start during the first day after birth.  By the time the child has reached three months of age it shows signs of having a mind of its own, and is capable of exercising thought.  It grasps for objects, and indicates its likes and dislikes.  At from eight to ten months it can utter several syllables, and at the age of one year should be able to say mama and papa; at two years it should be able to frame short sentences.

Weight of the Baby.—­ By the end of the sixth month the child’s weight should be double what it was at birth; that is, about fourteen pounds; at the end of the twelfth month be three times as much as at birth, or about twenty pounds.