BACTERIAL VARIETIES OF GANGRENE The acute bacillary forms of gangrene all assume the moist type from the first, and, spreading rapidly, result in extensive necrosis of tissue, and often end fatally. The infection is usually a mixed one in which anaërobic bacteria predominate. The anaërobe most constantly present is the _bacillus ærogenes capsulatus_, usually in association with other anaërobes, and sometimes with pyogenic diplo- and streptococci. According to the mode of action of the associated organisms and the combined effects of their toxins on the tissues, the gangrenous process presents different pathological and clinical features. Some combinations, for example, result in a rapidly spreading cellulitis with early necrosis of connective tissue accompanied by thrombosis throughout the capillary and venous circulation of the parts implicated; other combinations cause great œdema of the part, and others again lead to the formation of gases in the tissues, particularly in the muscles. These different effects do not appear to be due to a specific action of any one of the organisms present, but to the combined effect of a particular group living in symbiosis. According as the cellulitic, the œdematous, or the gaseous characteristics predominate, the clinical varieties of bacillary gangrene may be separately described, but it must be clearly understood that they frequently overlap and cannot always be distinguished from one another. #Clinical Varieties of Bacillary Gangrene.#--#Acute infective gangrene# is the form most commonly met with in civil practice. It may follow such trivial injuries as a pin-prick or a scratch, the signs of acute cellulitis rapidly giving place to those of a spreading gangrene. Or it may ensue on a severe railway, machinery, or street accident, when lacerated and bruised tissues are contaminated with gross dirt. Often within a few hours of the injury the whole part rapidly becomes painful, swollen, œdematous, and tense. The skin is at first glazed, and perhaps paler than normal, but soon assumes a dull red or purplish hue, and bullæ form on the surface. Putrefactive gases may be evolved in the tissues, and their presence is indicated by emphysematous crackling when the part is handled. The spread of the disease is so rapid that its progress is quite visible from hour to hour, and may be traced by the occurrence of red lines along the course of the lymphatics of the limb. In the most acute cases the death of the affected part takes place so rapidly that the local changes indicative of gangrene have not time to occur, and the fact that the part is dead may be overlooked. [Illustration: FIG. 22.--Gangrene of Terminal Phalanx of Index-Finger, following cellulitis of hand resulting from a scratch on the palm of the hand.]