TUMOR, in surgery, any morbid parasitic growth, generally, though not always, attended by swelling. Tumors are primarily divided into two classes, the first innocent, including non-malig nant, solid, benign, or sarcomatous, and the second malignant growths. Tumors of the first type occur in comparatively few tissues, and do not alter the adja cent parts unless the tumor produces pressure and partial inflammation; they have no tendency to ulcerate or slough, and, if extirpated by a surgical opera tion, they do not grow again. They vary considerably in structure, being fatty, cellular, fibrous, fibroid or tendonous, en cysted, vascular, cartilaginous, osseous, or fibro-cartilaginous. Fatty and carti laginous tumors often reach a size so large that they weigh many pounds. They should be excised while they are small. A tumor of the second type, on the contrary, may arise in almost any part of the body, though some parts are more liable than others to attacks. They
tend to propagate their morbid action to the adjacent parts, or, by means of the blood, even to spots remote from their formative seat; they ulcerate or slough, and, when extirpated by surgical opera tion, grow again, either at the original or some other place. The cancer and tubercle are leading types of malignant tumors. A third type of tumor, the semi-malignant, is intermediate between the first two, and includes some forms of sarcomic and of melanotic tumor, the painful subcutaneous tumor or tubercle, nievi, polypi, etc. Melanosis is commoner in horses than in the human subject, and chiefly in white or gray horses. Various tumors are inter-thoracic, affecting the heart, the lungs, etc. There are also tu mors of the brain, of the liver, the rec tum, etc.; and in women the uterus and the vagina are specially liable to be af fected with tumor.