Why Do We Stop Growing?
We eventually stop growing because certain of the cells of the body lose their ability of increasing in size and producing other cells. It is one of the marvels of the construction of the human body that this is so and one of the wisest provisions also. At first the cells of the body crave lots of food and increase in size, divide and then the parts go on growing until they become of a certain size, when they again divide and each part goes on growing, etc., and thus we grow. A growing boy needs more fond than a mature man, because he needs some of it to grow with, while the man only has to keep what growth he has going, i. e., alive.
We say this limit of growth is a wise provision of nature because if there were no limit to the size we might become, we would not know how large to build houses, barns, etc., or else we would have to build them so large to start with that we would be lost in them for a long time. We would constantly be forced to change these things and there would be no basis to reckon from. Dogs might be as big as elephants and then they would be of no use to us, or of what use would a dog as big as an elephant be to a boy of five years. You see it would not do at all to have this rule changed.