iarity with the striking peculiarities of these substances is such that we pass with the greatest readiness from one to the other, and treat them all in essentially suitable ways.
What do we know about things that are fit in an ever-changing environment? In the first place they are things which have had a long history, and though we are stillignorant of the conditions under which this history has been worked out, we do feel reasonably certain that all life is of a common stock, and that we have as good reasons for speaking of the brotherhood of living things as we have for speaking of the brotherhood of men. We know with much greater detail that fit things assimilate food, that they excrete wastes and that they secrete substances useful to themselves. We know too that they grow, repair wounds, and often restore very complex lost parts; that by a marvelous process of development they reproduce their kind from spores, gemmules, buds and eggs; and finally, we suspect that many of them have minds in some way like our own. We know with certainty that we ourselves have sensations, feelings, emotions, knowledge and the power to communicate much of all this to others. Strangest of all, we have a fairly complete equipment of self-knowledge, and we spend much of our time in thinking and talking about our origin and our destiny.
The anatomist tells us that things which do all this are composed of many complicated parts visible to the naked eye; the histologist analyzes these parts or tissues microscopically, and finds that they are made up of unit masses, the cells, or of the products of cells. From the embryologist we learn in detail how each of the myriad cells of the body comes from preexisting ones, and how by tracing development back to its earliest stages, we finally reach the egg. Cytology carries the dismemberment a step farther by discovering, classifying and naming, not only the minuter parts of the cell, but its very granules. Biological chemistry tells us what substances are found in the protoplasm; chemistry what elements are present and their proportion; physics that these elements are molecular in structure, that each molecule is made up of smaller units, the atoms, and finally, the newest physics of all dissects the atoms and promises to show that these, instead of being simple, are in reality constellations of electrons. When we consider that a single protein molecule may contain perhaps 2,304 atoms, more or less, that the number of protein molecules in a cell is unknown, that there are millions of cells to the man, we realize that our bodies are fearfully and wonderfully made, and that if our ears were sensitized to only a fraction of the rush and bustle within each protein molecule we should be deafened as with the roar of a Bessemer furnace.This analysis is far from complete, but thousands of men throughout the world are contributing, each the small share which he can,