#Moist Gangrene# is an acute process, the dead part retaining its fluids and so affording a favourable soil for the development of bacteria. The action of the organisms and their toxins on the adjacent tissues leads to a rapid and wide spread of the process. The skin becomes moist and macerated, and bullæ, containing dark-coloured fluid or gases, form under the epidermis. The putrefactive gases evolved cause the skin to become emphysematous and crepitant and produce an offensive odour. The tissues assume a greenish-black colour from the formation in them of a sulphide of iron resulting from decomposition of the blood pigment. Under certain conditions the dead part may undergo changes resembling more closely those of ordinary post-mortem decomposition. Owing to its nature the spread of the gangrene is seldom arrested by the natural protective processes, and it usually continues until the condition proves fatal from the absorption of toxins into the circulation. The _clinical features_ vary in the different varieties of moist gangrene, but the local results of bacterial action and the constitutional disturbance associated with toxin absorption are present in all; the prognosis therefore is grave in the extreme. From what has been said, it will be gathered that in dry gangrene there is no urgent call for operation to save the patient's life, the primary indication being to prevent the access of bacteria to the dead part, and especially to the surface exposed at the line of demarcation. In moist gangrene, on the contrary, organisms having already obtained a footing, immediate removal of the dead and dying tissues, as a rule, offers the only hope of saving life. VARIETIES OF GANGRENE #Varieties of Gangrene essentially due to Interference with the Circulation# While the varieties of gangrene included in this group depend primarily on interference with the circulation, it is to be borne in mind that the clinical course of the affection may be profoundly influenced by superadded infection with micro-organisms. Although the bacteria do not play the most important part in producing tissue necrosis, their subsequent introduction is an accident of such importance that it may change the whole aspect of affairs and convert a dry form of gangrene into one of the moist type. Moreover, the low state of vitality of the tissues, and the extreme difficulty of securing and maintaining asepsis, make it a sequel of great frequency.