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Show 52:6 X'ERICRANIUM. rsmcmnrrm. For example, the portion A, fig. 1, has been included in the trephine; but when the instrument had cut through the outer table, the inner table, B, being loose and splintered oil" from the firm part of the skull, yields to the pressure. There- ,fore, when we withdraw the saw occasionally, to clean it, we ii it be much exposed. If the pulsation of the dura ma- ter be very strong, and there be danger of its cutting on the sharp bone, small sindons of the same soft dressings may be introduced into the opening of the bone, and a due pres sure be kept on them, by a compress and bandage. ; 31.5: have to observe the degree of looseness of the circle included in it. Again, supposing that we have to operate at A, fig. 2, in order to elevate B, although the circle seems to be on the firm bone, yet we have to recollect that almost always, the lower table being very brittle, the inner table of the depressed portion is of more extent than the apparent field of the depressed portion B; and consequently, when we have cut through the outer table of A, we begin to depress and jar on 45"?)"7 U," Q tunnel" ‘1 g} the extremity of B. The great nicety of performing the operation of trepan, consists in observing well, in the first place, what point holds the bone firm ; and whether the larger depressed piece may be brought through the opening of the skull, when we have perforated in this place or that. The last advice I give relates to the use of the lever or elevators. Where there are lesser pieces which may be picked away, the operation of sawing may often, by raising these, be avoided; for the depressed piece may thus be entirely loosened, or we may then get the elevator so introduced as to raise the depressed bone. In my list of instruments, I have provided several of these elevators, and the meaning i8, that they should be very seldom used singly; for unless the one side of the bone be held from sinking and being dct pressed, whilst the other is elevated, it will be pressed down so as to injure the parts beneath. The lever may be used with advantage when the trephine is to be put on a piece of bone somewhat loose; for by that means the bone may be fixed and kept from jarring. The dressings used for the wound after trepan, are of the simplest kind. Slips of lint, imbued with oil or soft oint~ ment, are introduced under the flap, and on the dura mater. 52;; l-‘ND OF VOLUME FIRE! |