In the second year of life the gain in weight is very mueh less than in the first. In boys amt girls the gain is only about 2.5 kilos and from the third to the fifth year it decreases still more, to I to 2 kilos per an num. Al. the end of the fifth year boys have a weight of about Is kilos, girls of 17 kilos. From then on the weight of boys increases 2 to 3 kilos per annum to about the 11th year; then follows a period of increased growth, with a yearly gain of about S kilos from the fifteenth to the eighteenth year. The yearly weight in girls is about 2 kilos to the twelfth year; it then increases to 4 to , kilos from the thirteenth to the six teenth year. The gain in weight due to the processes of growth is prac tically completed by the end of the sixteenth year in girls and the nineteenth year in boys. The following table gives in round numbers the yearly growth in weight : Certainly only few individuals keep exactly the weight reached in the sixteenth to nineteenth year of life. The majority continuo to gain weight gradually mostly through retention of fat and increase of the muscles. For this reason, in establishing average values a slow increase in weight is noted until the twenty-fifth year. But this gradual change of the body cannot be designated any inure as "growth." Every healthy human being MUSi gain in weight up to the sixteenth to nineteenth year of life, but from that time on the weight depends on the individuality and on external accidental influences,—such as, for instance, the occupation and the food. The side curve in Fig. 64 illustrates this very clearly.
This curve illustrates the events as observed in a healthy youth. With seventeen years he had reached a weight of 60 kg. (I); with seventeen and a half years lie rose to 61.8 kg. (II) (Figs. 63 and 64); while preparing for an examination the weight dropped 2.6 kg. (III) in the course of three months. During two months' vacation the weight increased 800 Gm. (IV), to drop 21 kg. (V) during the next six months of hard studying. The next half year brought a gain of 3 kg. (VI) while serving in the army; then a febrile disease rapidly decreased the weight 1 kg. (VII), and in the next half year of lighter study a gain of 3', kg. (VIU) was noted.
The relative figures of growth are very interesting, aside from the absolute figures. in the first month of life the daily gain in weight is roughly 1 per cent. of the present body substance, in the middle of the first year about 0.3 per cent., and at the end of the first year still 0.15 per cent.; then it reaches a minimum in the fifth year, with about 0.03 per cent., to increase in the second great period of growth to 0.04 per cent. in girls and to 0.07 per cent. in boys. The ingestion of large amounts of food, frequently observed in growing boys from fourteen to eighteen years of age, is not caused by the growth, as is usually supposed, for tl.e daily gain is at this time only a few grams and in relation to the body substance is infinitesimal. The growth therefore cannot play an im portant role with regard to the processes of the metabolism.
Reviewing the total cause of the gain in weight, we can distinguish two periods of greater intensity of growth. The one occurs in the first year of life, the second in girls from the twelfth to the sixteenth year and in boys from the fifteenth to the eighteenth year (Fig. 65).
The curve of growth represents the picture of a double wave. The first period of growth may find its explanation in the continuance of the excessive foetal energy of growth; the second period coincides in boys and girls with the development of puberty, and it is probable that there exists a close relation between these two phenomena. The curves in Fig. 64 show distinctly the differences of the growth in weight of boys and girls (particularly of the girls from 13,- to 16 years of age). Fig. 65
illustrates particularly the variations in the intensity of the yearly gain in weight.
The determination of the total length of the body is best adapted to investigate the growth in length, since it results from the length of the legs, the pelvis, the spinal column, and the head, and expresses most distinctly the changes in the growth of all these parts. At the same time we obtain information about. the length of the single parts of the body, since this stands in a certain relation, although this relation is not quite constant for the different years of life. For instance, in the child going to school the length of the lower leg is stated to be 2S to 29 per cent. of the height, that of the upper leg 2S to 31 per cent.; the corre sponding figures for the lower arm and hand are 25 to 27 per cent., for the upper arm 18 to 19 per cent. These figures can only be regarded as approaching the average values, and only for the school period. From the following it may be seen how much these single proportions change during growth. The total length of a newborn baby is 4 times the length of the head, that of a two year old boy 5 times the height of the head, that of a boy six years of age 6 times the length of the head, that of a fifteen year old boy 7 times the length of the head, and that of the adult eight times the height of the head. These proportions can best be seen in Fig. Gti, taken from the book by Stratz, Der Kiirper des Kindes.
Numerous observations, chiefly made in maternity hospitals, in form us about the length of the body at birth. This length is 50 to 52 cm. in boys and 49 to 51 cm. in girls. At the end of the first year of life the total length reaches 70 to 75 cm. Only a few investigations have been conducted concerning the more exact course of the growth in length during the first year, probably because an exact determination of the length is very difficult in the infant. In order to accomplish this the infant, has to be placed on a table in such a way that its head a board fixed vertical to the plane of the table. Then one person has to hold head, neck, and shoulders in the proper position, it second person has to do the sante with regard to pelvis and knees, while a third person places a hoard on the soles of the feet vertically to the plane of the table. After the baby has been placed successfully in a good position it is removed, the position of the lower board is marked, and the distance of the mark from the upper board is measured. It is true that the tion in which the head, pelvis, knees, soles of the feet are placed is arbitrary to a certain extent, but single measurements peated at short intervals vary only a few millimetres, and the observers soon become accustomed to placing the body in a certain position, which will be nearly the same at the individual Measurements which I conducted in this manner have shown that the length of the body does not increase during the first three weeks when compared with the length at birth. Frequently even a decrease was noted. I was able to prove that the head of infants born at full term becomes somewhat elongated during parturition, which explains this remarkable phenomenon. Furthermore, a cephalfematoma is fre quently formed (Fig. 67, p. 425). These changes disappear gradually during the first three weeks, but they render it impossible to form an exact picture of the growth in this time. Since the deformity of the head was disregarded, the usual data about the length of the newborn exceed the true values by 1 to 2 cm., and the actual length of newborn boys must be assumed to be about 49 cm., and that of newborn girls 4S cm.