Malignant edema is essentially a specific form of _gangrene_ (see Chapter V), and is mentioned here rather because of its specific character. It is characterized by rapidity of spread and the specific nature of the exudate, as well as by the speedy destruction of the tissue involved, and by more or less gas formation. It is not the same as the gaseous phlegmons described by some German surgeons, yet partakes of their general character. _Gas phlegmons_ have been rarely noted, their peculiarity being formation not only of pus, but of more or less offensive gases, which escape when the phlegmon is incised. The gases are mainly due to the presence of _bacillus aërogenes capsulatus_, and gas phlegmons, as such, are to be regarded as instances of mixed or rarely pure infection. Malignant edema is known by the brownish discoloration of the overlying skin, which is streaked with blue where the overfilled veins show through it, while the underlying tissues are sodden with fluid and more or less inflated by the gaseous products of decomposition, so that the finger detects a firm crepitus, as is common in subcutaneous emphysema. From the wound, if there is one, flows a thin, foul-smelling secretion, which may also be expressed from the deeper layers. That the neighboring lymph spaces and nodes are actively involved is evident from the enormous swelling of the latter, as well as from the general condition of the patient. The rapid elevation of temperature with but trifling remissions remains constant until shortly before death. The tongue early becomes dry and cleaves to the palate, its surface being covered with a thick, foul fur. Patients early become apathetic, complaining only of pain and burning thirst. Delirium and coma usually precede death, which may occur in fifteen to thirty hours. After death the cadaver bloats quickly and putrefaction goes on with amazing rapidity. =Postmortem Appearances.=--At the seat of the lesion even muscles and tendons will be found macerated, bone denuded and surrounded by a putrid fluid, the entire region presenting a notable swelling and infiltration of soft parts with reddish fluids and stinking gases. The overlying skin will be stretched, and superficial blisters may deepen the intensity of the process. The veins are clogged with decomposed blood and broken-down thrombi, and in the heart and large vessels will be found putrid liquid as well as gas, to whose presence early and sudden death is probably due. =Prognosis.=--This is unsatisfactory, especially when the bacillus of malignant edema is alone at fault. Patients may escape with their lives, but always at the expense of more or less tissue destruction.