Pulmonary interstitial emphysema occurs more often than is generally realised. It can be found after severe contusion of the chest cage in the absence of rib fractures and it is frequently associated with pulmonary haemorrhage. Radiological evidence of pulmonary interstitial emphysema may be given not only indirectly by the presence of mediastinal emphysema or of a pneumothorax, but also directly by radiological signs in the lung. This is now confirmed by autopsy in our Case 2. The radiological signs in the lung may be observed either within an opacity caused by pulmonary haemorrhage or outside it. They are easier to perceive when the air is enclosed in sizeable spaces. The following appearances have been observed: (a) translucencies surrounded by a very thin wall, similar to emphysematous bullae; (b) translucencies surrounded by a slightly thicker marginal zone, suggestive of “air-filled pseudo-cysts” (c) translucencies with a characteristic sinuous outline as if formed by a number of smaller vesicles. S...