These general features are associated with certain microscopical characters found in the tumours or ulcers, so that the nature of any growth――whether malignant or otherwise――can be sometimes determined by the surgeon or physician, and sometimes by the pathologist or microscopist alone, but, as a rule, is most certainly settled by the physician or surgeon acting in conjunction with the microscopist. Yet, and this is important, not every cancer does actually destroy life. Surgeons of the greatest experience, such as the late Sir Alfred Pearce-Gould, have affirmed that undoubted cancers do occasionally undergo spontaneous cure, or at least arrest of growth, _even in the absence of any treatment_. Again, if excision is practised early, and sufficiently extensively, recurrence does not happen, in a certain proportion of cases. Finally, pain is no necessary or inevitable concomitant of cancer. In many cases pain is absent, or almost so; death may be due to mechanical consequences entailed by the growth rather than to destruction of any vital or sensitive part. Now, medical men are in the habit of splitting up the group or class of malignant growths (or “cancers”) into two subsidiary groups or classes. One of these is named Sarcoma; the other Carcinoma. Sarcoma is the name given to a group of malignant growths taking origin in the structures and tissues developed from the “middle layer” of the embryo: the growths themselves――sarcomata――partake the nature of the tissues formed from this middle layer. The other group, of carcinomata, consists of growths taking origin in, and partaking the nature of one or other of the two remaining embryonic layers and the structures developed from them. These two layers form respectively: (1) The skin and related structures, and (2) The lining of the tube passing through the body; its backwaters, out-growths and appendages.