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Page:Popular Science Monthly Volume 32.djvu/553

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blood or to appear secondarily at different places in the body of the same patient. The malignant tumors, on the other hand, are those which are not limited by a capsule. They reach out and involve all kinds of tissue which happen to be near them; they infect the blood, and new colonies form at points situated at a distance from the parent growth. There is hardly a doubt but that malignant growths are quite local at the outset, but, like red ants, the microbes make more and more nests in the same field. As with red ants, too, we often fail to eradicate the colony, because many members may be away from home at the time when the nests are destroyed.

Malignant tumors have been produced in the dog by inoculation from an infected dog, in the horse by inoculation from the dog, and the horse has been inoculated from the horse. We are afraid that cancer is inoculable between animals and man, and between man and man, but on this point medical literature at present furnishes little reliable testimony.

Why it is that the cancer microbes which enter a cut on the surgeon's finger do not regularly produce cancer in the surgeon is a fact not easily explained. It is, however, a well-known fact, that certain other species of microbes are very particular about sites for their homes, and we may suppose that the cancer microbe finds a suitable field for growth in a relatively small number of persons.

When a malignant tumor is developing at any one point the lymphatic vessels in the vicinity are involved at an early date, and they eventually serve as channels for the passage of the disease into the blood.

If a far advanced primary growth of cancer could be stained in its entirety with a black dye, and if the patient were transparent, we should probably see that the tissues round about the growth were dusky, and that a thin, smoky coloring extended through the lymphatic vessels to the veins into which they empty. As a malignant tumor increases in size at its original situation the nerve filaments are pinched, and pain is caused as a rule; but sometimes the growth will progress with little or no accompanying pain.

When an operation by a competent surgeon is performed during the early stages of the disease, it may be eradicated completely; and even in cases in which considerable headway has been gained the surgeon is able to give long periods of immunity from the return of the growth. Patients, however, are unfortunately familiar with the traditions of old-time wound treatment, and the dread of an operation is so great that they seldom act in the matter until it is too late to hope for a cure.

The operation for the removal of a malignant growth causes no real suffering when it is done by the surgeons of to-day, who employ anesthetics for preventing pain during an operation and antiseptics for limiting inflammation afterward. The scientific antiseptic methods of wound treatment deal directly with species of microbes with which