Another very curious thing in accidents is the instantaneity with which muscles which are _ordinarily_ under the dominion of the will, become reluctant to obey it, or altogether repudiate its authority. In all fractures, of course, the most material thing is absolute repose; and there is very little chance of a man moving his rib when it is broken. He instinctively begins to expand his chest, for the admission of the necessary air, by other muscles, usually to the exclusion of those which are attached to the broken bone.
The Lung, which may be considered as a series of tubes, some conveying blood, and others air, is often wounded; but the blood immediately stops the leak, from its tendency to coagulate when out of the vessels; and no harm ensues. Occasionally, however, a circumstance occurs, which, until it is understood, appears curious and alarming. Either from the extent, the scratching of the surface, or some other peculiarity in the wound of the lung, the air escapes from it, and the patient is as it were blown up, as to the chest, neck, and face, by the air impelled from the lung beneath the skin into the connecting tissue, exactly in the same manner as the butcher does when he is preparing veal. This blowing-up is called, from the Greek word for it, _Emphysema_; and it was on this feature in these accidents that Mr. Abernethy wrote a short paper.
There is not much which is absolutely new in it. It is chiefly remarkable for the clear manner in which it places before us what is required, as distinguished from what is officious and unnecessary, and, in fact, reduces the treatment to that of ordinary cases, with one clearly defined modification.
He shows his familiarity with Pneumatics, so far as they are touched by the case, just as he does his knowledge of Chemistry elsewhere. The exceptional cases, in which the air is confined in the chest, the mode of procuring it an exit by operation, and the condition regulating this proceeding, are very simply and clearly laid down.
The paper also contains remarks on the collapse of the lungs when the chest is opened, and on certain exceptions which have been observed, which, from their general interest and suggestive character, will well repay an attentive perusal.