64 SURGERY. 



the exfoliation of the bone, which is a tedious process. The symp- 

 toms denoting the formation of this dangerous abscess, affect the 

 system as wefl as the part ; and the patient would manifest the same 

 restlessness, rigor, and fever, which attend the formation of pus m 

 other parts of the body. 



TREPHINING. 



The scalp is first to be cleanly shaved; and if a wound already 

 exist, the cranium may be exposed simply by enlarging it ; but if 

 no previous wound exist, an incision is to be made, of a crucial, 

 triangular, or semicircular shape,— the latter being most preferred. 

 The pericranium is then to be detached by a scraper, unless the 

 trephine have an additional means for removing it. That portion of 

 the cranium should be selected which is sufficiently near the injured 

 parts to allow of elevation of the fragments, by the introduction of 

 an elevator, and at the same time to be sufficiently firm to bear the 

 pressure of the trephine. The sinuses of the dura mater, the occi- 

 cipital cross, and the course of the middle artery of the dura mater 

 are to be avoided. The centre pin of the trephine is to be withdrawn, 

 after a groove is made sufficiently deep for the play of the teeth of 

 the instrument ; and great care is to be taken, lest the trephme saw 

 through the bone unequally, owing to the want of parallelism of the 

 two tables of the skull. The progress of the operation is to be 

 cautiously watched, and the depth of the groove made by the 

 trephine, ascertained by a toothpick or a small probe. The button-^ 

 like portion of bone frequently comes away in the trephine; it 

 not, it is to be removed by a forceps or elevator ; the rough edges 

 (should any exist) of the internal table, are to be taken away by an 

 instrument called a lenticular. Through the opening thus made, 

 the elevator may be introduced, or the extravasated blood may 

 escape. The opening is subsequently filled up by a dense mem- 

 brane, formed by the pericranium and dura mater. The edge of the 

 opening is somewhat altered by absorption, and some deposit of 

 bone. In some instances of compound fracture of the skull, a promi- 

 nent angle may be sawed off* with Hey's saw, and thus an opening 

 be formed sufficiently large for the admission of the elevator, or the 

 exit of the bloody clot. 



INJURIES AND DISEASES OF THE FACE, NOSE, 



ANDMOUTH. 

 Wounds of the face are usually attended with considerable he- 

 morrhage, which sometimes requires the tying of an artery. Care 

 is required to approximate the edges, in order to prevent deformity 

 and an ugly cicatrix. When the supra-orbital nerve is injured, 

 vision is impaired ; when the portio dura nerve is cut, paralysis 

 of the muscles upon one side of the face results. 



