| OCR Text |
Show or W" bum-SN? . Ta 320 ranlcmmmu. PERICRANIUM. at present used of great size) be not applied on the sound bone, without necessity. 52]. free of its edge, or before the instrument has cut through we shall be pressing on the loose bone, and endangering the dura. mater. Suppose that the depressed bone is fixed as in (1), then we apply the perforator near the margin, and one half of the cir» cular saw operates on the depressed portion, the other on the sound bone. The sound bone is loose before the other, in which case the object of the operation is accomplished ; for by getting out the portion (2), the elevator or lever may bt' introduced under the depressed portion. If it shall appear that in the end it may be necessary to fix a trephine on the insulated portion of bone, it is better to do it at first; because after a circular portion is taken out on the margin of the depressed bone, it may have become loose, and will no longer bear the pressure of the instrument upon it, although, owing to its shelving edges, it is still impossible [fir/WI lllllltlltltl'll , If A be a. depressed piece of bone, quite below the level of the skull, it may happen, that, owing to the shattered part G, A is loose, and it may be raised simply by the lever introduced at B. But if this should not do, and the bone should he too firmly fixed for this simpler operation, then the tree phiue is to be applied. The common directions are such as would make us set it at D. But as by this means the whole space of the skull from E to D would be laid open, I would if possible apply it at F, upon that part of the bone which is to be taken away ; and as the bone is firm and wedged here, i should do this with safety. I should expect that by tak- ing out the circular portion 1', I should be enabled to piCk away the pieces, G, and thus open the fracture from F to E, and loosen the whole extent of the base of the depressed piece, by which it was held firm. But should this not be the ease, then we might apply the trephine at D, on the sound bone. But again, should A not be so far reduced below the level of the sound bone as to be free of the trephine (as indeed it seldom will he), should the edge of the depressed bone shCIVC nuder the firm bone, as it generally does, then we must keep to elevate the bone. Sometimes the portion of the inner table under the trephine (where we are operating on the sound outer table) may be loose, and we may be working it against the dura mater long before the instrument has passed through at any one point. WON! Ml |
