#Acute Emphysematous# or #Gas Gangrene# was prevalent in certain areas at various periods during the European War. It follows infection of lacerated wounds with the _bacillus ærogenes capsulatus_, usually in combination with other anaërobes, and its main incidence is on the muscles, which rapidly become infiltrated with gas that spreads throughout the whole extent of the muscle, disintegrating its fibres and leading to necrosis. The gangrenous process spreads with appalling rapidity, the limb becoming enormously swollen, painful, and crepitant or even tympanitic. Patches of coppery or purple colour appear on the skin, and bullæ containing blood-stained serum form on the surface. The toxæmia is profound, and the face and lips assume a characteristic cyanosis. The condition is attended with a high mortality. Only in the early stages and when the infection is limited are local measures successful in arresting the spread; in more severe cases amputation is the only means of saving life. #Cancrum Oris# or #Noma#.--This disease is believed to be due to a specific bacillus, which occurs in long delicate rods, and is chiefly found at the margin of the gangrenous area. It is prone to attack unhealthy children from two to five years of age, especially during their convalescence from such diseases as measles, scarlet fever, or typhoid, but may attack adults when they are debilitated. It is most common in the mouth, but sometimes occurs on the vulva. In the mouth it begins as an ulcerative stomatitis, more especially affecting the gums or inner aspect of the cheek. The child lies prostrated, and from the open mouth foul-smelling saliva, streaked with blood, escapes; the face is of an ashy-grey colour, the lips dark and swollen. On the inner aspect of the cheek is a deeply ulcerated surface, with sloughy shreds of dark-brown or black tissue covering its base; the edges are irregular, firm, and swollen, and the surrounding mucous membrane is infiltrated and œdematous. In the course of a few hours a dark spot appears on the outer aspect of the cheek, and rapidly increases in size; towards the centre it is black, shading off through blue and grey into a dark-red area which extends over the cheek (Fig. 23). The tissue implicated is at first firm and indurated, but as it loses its vitality it becomes doughy and sodden. Finally a slough forms, and, when it separates, the cheek is perforated. Meanwhile the process spreads inside the mouth, and the gums, the floor of the mouth, or even the jaws, may become gangrenous and the teeth fall out. The constitutional disturbance is severe, the temperature raised, and the pulse feeble and rapid. The extremely fœtid odour which pervades the room or even the house the patient occupies, is usually sufficient to suggest the diagnosis of cancrum oris. The odour must not be mistaken for that due to decomposition of sordes on the teeth and gums of a debilitated patient.