As determined by the volume, the embryo increases more than ten thousand times in size during the first month of intra-uterine life.

At birth the average weight is six and a half pounds; at the end of the first year eighteen and a half pounds, a gain of twelve pounds; at the end of the second year twenty-three pounds, a gain of four and a half pounds.

The growth is cooerdinated, the size of the single organs bearing a definite ratio, which varies within slight limits, to the size of the body, a large individual having organs of corresponding size.

Knowing that the capacity of growth is one of the inherent properties of living matter, it is much easier to understand the continuance of growth than its cessation.

It is impossible to avoid the conclusion that there is some internal mechanism of the body which controls and regulates growth.