=Causes.=--The causes of tumors are almost wholly unknown. There is no other branch of medicine which is receiving more scientific study the world over than cancer, and some definite and helpful knowledge may soon be expected. A cancer can be communicated by introduction of cancerous material into healthy tissues. This and other reasons have led many to believe that the disease was caused by a special germ; a chemical cause is thought to be the origin of cancer by other authorities. Neither of these theories has been substantiated and we are still completely at sea in the matter. Cancer appears to be excited sometimes by local irritation, as in the lip by the constant irritation of the hard, hot stem of a clay pipe; cancer of the tongue by the irritation of a rough, sharp tooth. Blows and injuries are also occasional agencies in the development of cancer. Malignant growths not rarely arise from moles and warts. =Treatment.=--Early removal by the knife is the only form of treatment which is to be considered in most cases. Delay and neglect are suicidal in malignant disease. Cure is successful in just so far as the operation is done early. If dread of surgical operation were not so prevalent, the results of removal of cancer would be immeasurably better. The common, bad results of operation--that is, return of the disease--are chiefly due to the late stage in which surgeons are compelled to operate through the reluctance of the patient and, strangely enough, often of his family medical man. Cancer should be removed in so early a stage that its true nature can often not be recognized, except by microscopical examination after its removal. If Maurice Richardson's rule were followed, many cancers would never occur, or would be removed before they had developed sufficiently to show their nature. All treatment by chemical pastes and special remedies is simply courting fatal results. Most special cures advertised to be performed in sanitoriums are money-getting humbugs. Even the X-ray has proved useless except in the case of most superficial growths limited to the skin or when directed against the scar left by removal of a cancer; and while the growth may disappear during treatment, in a large proportion of cases there is a recurrence. But when tumors are so far advanced that removal by the knife is inoperable, then other means will often secure great relief from suffering and will prolong life for a very considerable period in many cases.