To be robust the newly born infant must have a certain average length and weight. The length varies between sixteen and twenty-two inches, and the weight between six and eight pounds.

From the first day, growth or increase in length and weight steadily progresses according to certain definitely fixed rules.

Length increases most rapidly during the first week of life; afterward the progress is almost uniform up to the fifth month, and then it becomes less rapid, though still uniform, until the end of the twelfth month. These facts may be seen in the following table:

During the second year the increase is from three to five inches; in the third from two to three and a half inches; in the fourth from two to three inches, and from this age up to the sixteenth year the average annual gain is from one and two-thirds to two inches.

In the first three days of life there is always a loss of weight, but by the seventh day the baby should have regained weight and be as heavy as at birth. The period of most rapid gain in this respect is during the first five months of life. The maximum is attained during the second month, when the increase is from four to seven ounces each week. Throughout the next three months the increase amounts to about five ounces per week, and in the remaining months of the first year, from two to five ounces.

The subjoined table shows the average rate of gain:

Increase in weight and stature are so closely re-lated to the quality and quantity of food supplied to the infant, and to the processes of digestion, absorption and assimilation, in other words, are such perfect indices of proper nutrition or the reverse, that it is important to keep a record, during the first year at least, of these two features of development. This can be graphically accomplished, and so more readily appreciated, by placing the data upon a chart, such as shown by Fig. 2. Here the average normal weight-gain and increase in length are indicated respectively by the blue and red lines. The figures at the top of the main chart denote the age by. weeks, the heavy vertical lines mark periods of four weeks, the lighter, periods of one week. The figures on the left are numerals of weight, the heavy horizontal lines mark pounds, the lighter, quarter-pounds. The intersection of these sets of lines form squares, one for every weight and age. In making the record mark a dot in the square corresponding to the weight and age. At the next observation make a second dot in the proper square, and so on. These dots are connected by a line, and a comparison of this line with the test blue line shows at once whether or not the special infant's weight-gain is normal. Gain in length is marked in the same way, near the red line, in the upper division of the chart; the figures, already mentioned as indicating the age in weeks, applying equally to this part of the record, while the numbers at the extreme top of the chart indicate length in inches.

Fig. 2. - Chart for Recording Infant's Gain in Weight and Length.

From the first to the tenth year there should be a yearly gain of at least four or five pounds. After, to the sixteenth year, of about eight pounds in the same period.

Parents frequently overestimate the weight of their children by placing them upon the scales when completely dressed. To be accurate, the weight of the clothing must be subtracted. This may be estimated at about three pounds for a child of three to five years, four pounds for one of eight years, and eight pounds at fifteen years.

Another reliable evidence of the proper progress of development is the increase in the girth of the chest. In an infant weighing seven pounds and measuring nineteen and a half inches at birth, the girth should be a little over thirteen inches. By the fourth month it should be fifteen inches; by the sixth, sixteen; by the twelfth, about seventeen; by the fifth year, twenty-one, and by the sixteenth year, thirty inches.

As already mentioned, the proportions of the different members of the frame in infancy differ materially from those of adolescence.

Primarily the head and secondarily the body are large when compared with the arms and legs, but in the progress of healthy development this disproportion is gradually lessened until the perfect human figure is attained. This developmental process, however, does not affect all parts of the body equally, as may be seen in the accompanying diagram.* (Fig. 3.)

The description is so well put in the journal from which this figure is taken that I cannot do better than quote it word for word:

Fig. 3. - Diagram Showing Relative Stature from 1 to 22 Years of Age.

"The six figures represent the average relative stature of males of the ages of one, five, nine, thirteen, seventeen, and twenty-two years. It will be noticed that the figures all stand on a level plain. The tops of the heads are connected by a dotted line, and the height of each figure is divided into four equal parts, the points of division being connected with the corresponding ones in each figure. If the rate of growth were uniform the dotted lines connecting the heads would, of course, be straight if a child for every year were included in the rank. But in the earlier years the growth is much more rapid than it is later, and hence the line is a curve, rising quite suddenly at the first, and becoming flatter toward the end of growth. It is to be understood that these are all averages, including, but not showing, the extremes of slowness and rapidity of growth as well as fitfulness of growth. The diagram also shows the different development of different parts of the person. The head, for instance, in the child of one year is nearly one-fourth of the whole height; that of the adult is about two-thirteenths, or, to use the phrase of artists, the little child is not much more than four heads • high, while the adult of twenty-two is about six and one-half heads high; and even this is a much larger head than the average adult has. Notice that the third dotted line, marking one-half of the total height, crosses the navel in the infant, while in the adult the half height mark is but little above the juncture of the legs and the body, which shows how much larger, proportionately, the body of an infant is than an adult's. If this same line be followed it will be noticed that it keeps well up in the abdomen until after the age of nine. Between that age and puberty the growth of the lower extremities is usually very rapid, and the well-known 'shooting up' of boys and girls takes place, the whole person growing, but the lower part in particular. Similar changes of location will be noticed by following the quarter-lines, but the changes are not so abrupt."

*"Babyhood," Vol. II. page 311. Paper by Leroy M. Yale, M. D.