The nomenclature of ulcers is much involved and gives rise to great confusion, chiefly for the reason that no one basis of classification has been adopted. Thus some ulcers are named according to the causes at work in producing or maintaining them—for example, the traumatic, the septic, and the varicose ulcer; some from the constitutional element present, as the gouty and the diabetic ulcer; and others according to the condition in which they happen to be when seen by the surgeon, such as the weak, the inflamed, and the callous ulcer. So long as we retain these names it will be impossible to find a single basis for classification; and yet many of the terms are so descriptive and so generally understood that it is undesirable to abolish them. We must therefore remain content with a clinical arrangement of ulcers,—it cannot be called a classification,—considering any given ulcer from two points of view: first its cause, and second its present condition. This method of studying ulcers has the practical advantage that it furnishes us with the main indications for treatment as well as for diagnosis: the cause must be removed, and the condition so modified as to convert the ulcer into an aseptic healing sore.A. Arrangement of Ulcers according to their Cause. Although any given ulcer may be due to a combination of causes, it is convenient to describe the following groups:Ulcers due to Traumatism. Traumatism in the form of a crush or bruise is a frequent cause of ulcer formation, acting either by directly destroying the skin, or by so diminishing its vitality that it is rendered a suitable soil for bacteria. If these gain access, in the course of a few days the damaged area of skin becomes of a greyish colour, blebs form on it, and it undergoes necrosis, leaving an unhealthy raw surface when the slough separates.Heat and prolonged exposure to the Röntgen rays or to radium emanations act in a similar way. The pressure of improperly padded splints or other appliances may so far interfere with the circulation of the part pressed upon, that the skin sloughs, leaving an open sore. This is most liable to occur in patients who suffer from some nerve lesion—such as anterior poliomyelitis, or injury of the spinal cord or nerve-trunks. Splint-pressure sores are usually situated over bony prominences, such as the malleoli, the condyles of the femur or humerus, the head of the fibula, the dorsum of the foot, or the base of the fifth metatarsal bone. On removing the splint, the skin of the part pressed upon is found to be of a red or pink colour, with a pale grey patch in the centre, which eventually sloughs and leaves an ulcer. Certain forms of bed-sore are also due to prolonged pressure.