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A considerable pressure or contusion of the chest, or any violent concussion of the lung, may produce a laceration in that viscus, without injury being done to the parietes of the thorax, and may give place to the infiltration of air into the areolar texture, interlobular emphysema. Laeunec has described another species of emphysema of the lungs, Vesicular emphysema, Aeropneumonasie, Aeropneurnonectasie of Piorry, consisting in excessive dilatation of the air-cells, some of which become as large as hemp-seed,ultimately break, and give rise to irregular vesicles at the surface of the lung, some of which are as large as a hazel-nut. Physical signs. The thorax externally, generally or locally, appears unnaturally convex and prominent. The intercostal spaces are widened, but depressed. The inspiratory efforts are increased. The sound on percussion is morbidly clear, but not tympanitic. On auscultation, the inspiratory murmur is feeble or suppressed. The expiration, which is more frequently audible, is prolonged, laborious and wheezing. There are no certain physical signs which can distinguish interlobular emphysema from the vesicular. Emphysema under the pleuro-pulmonalis is termed, by Piorry, Aerethmopneumonie.