2o8 Kc"M LiJ?rumnit for Trepanning. 



tion, the bone at that fide to which it is moft inclined will 

 fooneft give '.vay, and confequently the brain may be injured 

 before the furgeou is apprifed of it. Such accidents, it is 

 well known, have frequently happened. Sometimes, too, 

 the centre-pin, from agitation or inattention of the furgeon, 

 -has been left in the inllrument to the end of the operation, 

 and, after pafling through the bone, has perforated the brain. 



Befides thcfe, and feveral other obvious objeftions, the 

 number of neceflary auxiliary inftruments fufficiently evinces 

 the propriety of attempting to fimplify and improve the pre- 

 fent mode of operating. 



The manner of perforating the fkuU by the inftruments 

 now in ufe is, firft, with the perforator, to make a fniall hole 

 in the bone of a fufficient depth to receive the centre- pin of 

 the faw, then to apply the inftrument, and to continue faw- 

 ing till the groove is deep enough to preferve the inftrument 

 fteadily without the centre-pin : the inftrument then is with- 

 drawn, and the pin removed by means of the key. The 

 furgeon now proceeds to finifli the operation, and, having 

 replaced the inftrument, works through the bone with the 

 grcateft caution, taking care to withdraw and replace the 

 initrument from time to time, in order not only to clear 

 away the duft that fills up the teeth of the faw, but to dif- 

 cover whether the portion of bone to be removed is nearly 

 feparated. 



By this way of operating it is evident a confiderable por- 

 tion of the time is taken up even in preparing for the opera- 

 tion, befide what ia loft during the courfe of it. To fave time 

 in this, as in every other operation, muft be confidered as a 

 matter of great confequence both to the patient and furgeon. 

 With a view to ftiow how this may be accompliftied, it will 

 be neceffary to mention in what manner the operation may 

 be conduced with the inftrument now to be propofeil. " 



The patient being prepared for the operation, and the in- 

 ftrument applied, as in the plate, care muft be taken to make 

 the fawinor-teeth round the whole circumference touch the 

 furface of the bone equally. This can eafily be done ; for, 

 thouoh the inequality of the bones on which the inftrument 

 is placed be fuch as to prevent the faw from acting on all 



pointji 



