We have found the following method satisfactory in out-patient practice. The patient lying on a couch, the limb is raised about eighteen inches and kept in this position for five minutes--till the excess of blood has left it. With the limb still raised, the ulcer with the surrounding skin is covered with a layer, about half an inch thick, of finely powdered boracic acid, and the leg, from foot to knee, excluding the sole, is enveloped in a thick layer of wood-wool wadding. This is held in position by ordinary cotton bandages, painted over with liquid starch; while the starch is drying the limb is kept elevated. With this appliance the patient may continue to work, and the dressing does not require to be changed oftener than once in three or four weeks (W. G. Richardson). When an ulcer becomes acutely _inflamed_ as a result of superadded infection, antiseptic measures are employed to overcome the infection, and ichthyol or other soothing applications may be used to allay the pain. The _phagedænic ulcer_ calls for more energetic means of disinfection; the whole of the affected surface is touched with the actual cautery at a white heat, or is painted with pure carbolic acid. Relays of charcoal poultices are then applied until the spread of the disease is arrested. For the _irritable ulcer_ the most satisfactory treatment is complete excision and subsequent skin-grafting. CHAPTER VI GANGRENE Definition--Types: _Dry_, _Moist_--Varieties--Gangrene primarily due to interference with circulation: _Senile gangrene_; _Embolic gangrene_; _Gangrene following ligation of arteries_; _Gangrene from mechanical causes_; _Gangrene from heat, chemical agents, and cold_; _Diabetic gangrene_; _Gangrene associated with spasm of blood vessels_; _Raynaud's disease_; _Angio-sclerotic gangrene_; _Gangrene from ergot_. Bacterial varieties of gangrene. _Pathology_--clinical varieties--_Acute infective gangrene_; _Malignant œdema_; _Acute emphysematous_ or _gas gangrene_; _Cancrum oris_, _etc_. Bed-sores: _Acute_; _chronic_. Gangrene or mortification is the process by which a portion of tissue dies _en masse_, as distinguished from the molecular or cellular death which constitutes ulceration. The dead portion is known as a _slough_. In this chapter we shall confine our attention to the process as it affects the limbs and superficial parts, leaving gangrene of the viscera to be described in regional surgery. TYPES OF GANGRENE Two distinct types of gangrene are met with, which, from their most obvious point of difference, are known respectively as _dry_ and _moist_, and there are several clinical varieties of each type. Speaking generally, it may be said that dry gangrene is essentially due to a simple _interference with the blood supply_ of a part; while the main factor in the production of moist gangrene is _bacterial infection_.