It has been said that we must be regulated in our proceedings very much by the existence or not of external wound; that we must be cautious in cutting down upon fractures of the cranium where there is no wound, and so converting a simple into a compound fracture. In fact, so much is the danger increased, it is alleged, by the existence of wound, that the symptoms must be very urgent indeed which would demand division of the integuments in order to admit of examination of the fracture, the application of the trephine, or the elevation of the bone; whilst, on the contrary, if the fracture is exposed by the accident, very slight symptoms will fully warrant performance of the operation of trephine. In other words, it is said that simple fractures should be left to nature, unless under very urgent and alarming circumstances, and that compound ones ought almost always to be interfered with. But the facts are otherwise. The greatest danger of compound fractures of the cranium does not arise from the admission of air. It is not the wound of the scalp, but the mechanical irritation of the brain and its membranes that proves dangerous. Injuries of the cranium inflicted by sharp bodies, such as divide the scalp and cause compound fractures, are generally attended with splintering of the internal table, and require the trephine. The existence of this sort of fracture of itself, without a single bad symptom, without any present disturbance of the sensorial functions, is a sufficient warrant for the application of the trephine, so as to permit the removal of the detached portions of the inner table: and this should be done before inflammatory symptoms have shown themselves. The brittleness of the internal layer of the skull is well known. In fractures inflicted with sharp and pointed instruments, as a bayonet or pike, the corner of a sharp stone, or the heel of a horse’s shoe, the external opening is often very small, it is a mere puncture; in the bone there is a central depression, from which fissures proceed around in a radiated form, and hence the injury has been termed punctured, or starlike fracture. But though the external wound is apparently insignificant, the vitreous table is extensively separated, and, perhaps, broken into innumerable minute and sharp spicula. These sharp portions are driven down upon the dura mater, and by them the membrane is often severely lacerated. If these be not removed soon after the accident, inflammatory action is almost invariably lighted up on the surface of the brain; and we cannot expect to allay or avert such action by general antiphlogistic means, however energetically applied, so long as their exciting cause remains. It is in such cases, I repeat, that the operation of trephining is imperiously called for. Sometimes, however, patients are found to recover from punctured fracture of the cranium, without the operation having been performed, as in the following case, the