The most strikingly suggestive proof of the native-born character of cancer comes from two of its biologic characters. The first is that its habit of beginning with a mass formation, rapidly deploying into columns and driving its way into the tissues in a ghastly flying wedge, is simply a perfect imitation and repetition of the method by which glands are formed during the development of the body. The flat, or epithelial, cells of the lining of the stomach, for instance, begin to pile up in a little swarm, or mass, elongate into a column, push their way down into the deeper tissue, and then hollow out in their interior to form a tubular gland. The only thing that cancer lacks is the last step of forming a tube, and thereby becoming a servant of the body instead of a parasite upon it. Nor is this process confined to our embryonic or prenatal existence. Take any gland which has cause to increase in size during adult life, as, for instance, the mammary gland, in preparation for lactation, and you will find massing columns and nests of cells pushing out into the surrounding tissue in all directions, in a way that is absolutely undistinguishable in its earlier stages from the formation of cancer. It is a fact of gruesome significance that the two organs--the mammary gland and the uterus--in which this process habitually takes place in adult life are the two most fatally liable to the attack of cancer. Another biologic character is even more striking and significant. A couple of years ago it was discovered by Murray and Bashford, of the English Imperial Cancer Research Commission, that the cells of cancer, in their swift and irregular reproduction, showed an unexpected peculiarity. In the simplest form of reproduction, one cell cutting itself in two to make two new ones, known as mitosis, the change begins in the nucleus, or kernel. This kernel splits itself up into a series of threads or loops, known as the chromosomes, half of which go into each of the daughter cells. When, however, sex is born and a male germ-cell unites with a female germ-cell to form a new organism, each cell proceeds, as the first step in the process, to get rid of half of these chromosomes, so that the new organism has precisely the normal number of chromosomes, half of which are derived from the father and the other half from the mother germ-cell. This, by the way, is the mechanical basis of heredity.