I. CANCER OF THE MOUTH The term cancer of the mouth is commonly used to define those malignant tumors which arise in the mucous membranes of the oral cavity beginning anteriorly at the mucocutaneous junction of the lips and extending posteriorly to the level of the free edge of the soft palate, the tonsil and the base of the tongue. Cancer of the mouth may be divided into several varieties based on the anatomic site of the origin of the tumor; namely, lip, cheek, gum, floor of mouth, tongue, palate and tonsil. From the practical point of view growths arising in these different areas present distinct clinical problems especially with regard to treatment, and in the evaluation of an individual case it is essential that the primary site of origin of the tumor be definitely determined. ETIOLOGY Cancer of the mouth comprises about 4 per cent of all human cancer,