Page:Popular Science Monthly Volume 71.djvu/221

Rh with the growth and progress of the individuals about us. We overlook the fact that the progress which each individual makes is the result of accumulation. It is as if money was put into the savings-bank; it grows and becomes larger, but the rate of interest does not alter. So too with us; we see there is an accumulation of this wealth of organization which gives us our mature power. But as that accumulation goes on, our body seems to become, as it were, tired. We may compare it to a man building a wall. He begins at first with great energy, full of vigor; the wall goes up rapidly; and as the labor continues fatigue comes into play. Moreover, the wall grows higher, and it takes more effort and time to carry the material up to the top of the wall, and to continue to raise its height, and so, as the wall 400% grows higher and higher, it grows more slowly and ever more slowly, because the obstacles to be overcome have increased with the very height of the wall itself. So it seems with the increase of the organism; with the increase of our development, the obstacles to our growth increase. How that is I shall hope to explain to you a little more clearly in the next lecture.

We have one more slide, which I would like to show you. It indicates the rate of growth in man before birth as far as it can be indicated without better knowledge. The time intervals in the diagram correspond to the so-called lunar months—the ten lunar months of prenatal life. Of our early development we know very little so far as statistics are concerned, but from the third month onward we have some records. It is found that from the third to the fourth month the increase is 600 per cent. Just contrast that with 200 per cent, added in one year after birth; 600 per cent, in one month against 200 per cent, in one year. From the fourth to the fifth month it is scarcely over 200 per cent. It then becomes only a little more than 100. In the' seventh month, less than 100; and finally in the ninth and tenth months, it