2IO THE SCIENTIFIC MONTELT
greatest technical progress hag been accomplished and may be expected to bring the best results in the futare by attacking the problem on the basia of a dispassionate philosophical analysis of reality. This analysis transforms thnnder and lightning, which at first called forth only feel- ings of awe and fear, into phenomena of electricity, acoustics and optics, and teaches ns their oneness with the phenomena which help to maintain life. The growth of bacteria, which cause disease and death, on the one hand, is seen to play a wider rdle in the economy of life, to be indis- pensable for the maintenance of life in the higher animals.
It is not otherwise with the subject on which I have been asked to write. What at first we consider a disease, a scourge which fills us with fear and despair, will be seen to be but a particular phenom- enon of growth comparable in a certain respect to the development of the egg into the adult> to the restitution of an extremity in one of the more primitive amphibia and to the healing of the wound in a human body after a cut or a bruise.
In cancer we deal with an essentially similar phenomenon — ^with the multiplication of the small units of our body, the cells. In a definite, usually sharply circimiscribed and relatively small area such cells begin to proliferate; they multiply to an unusual degree; they make their way into the deeper parts of the body, destroy the neigh- boring tissues, penetrate often into lymphatics or blood vessels, are carried to distant parts of the body — ^lung, liver or elsewhere — settle here and give origin to secondary growths, the so-called metastases. Not all new formations of this kind, which are generally called tumors, are equally destructive. Some merely grow slowly and form a promi- nence without penetrating into neighboring tissues. These are the so-called benign tumors. The destructive tumors are called cancers. Almost any tissue in the body, almost any cells may, under certain conditions, begin to grow in this malignant, cancerous manner and, according to the kinds of cells that have thus proliferated, different types of cancer have been distinguished, as, for instance, carcinoma — the cancer of the cells covering the surface of the body and the body cavities, the epithelial cells; and sarcoma — the cancer of the tissues connecting the various surface and glandular structures of the body. But these are, for our purposes, differences of minor importance. The essential fact is this : in cancer we are dealing with a cell multiplication similar to that which leads to the building up of the normal organism^ the difference between normal growth and cancerous growth being as follows :
During the development from the egg to the adult organism, the multiplying cells and the developing tissues show a definite relation to one another, which is essentially hereditarily fixed. In cancer, however, certain cells or tissues fall out of this normal scheme of predetermined