T R E 



T R E 



»niinary niglit-cap of fiifficient fize to be put on with 

 facility. It may be fecured with bits of tape, which are to 

 te tied under the jaw. 



The aperture in the (kull ufually becomes clofed with 

 foft granulations, which flowly acquire :■ hard confiftence. 

 Thefe almoft conftantly grow from ir;- edge of the per- 

 foration, and feldom from the furface of the dura mater. 

 While the cicatrix is foft, it ftiould be protefted from ex- 

 ternal injury with a thin piece of horn or metal. Ex- 

 foliations from the margin of the perforation fometimes re- 

 tard the healing of the wound ; but now that the praftice 

 of dreffing with dryinj; fpirituous applications has been ex- 

 ploded, and the removal of any part of the fcalp is con- 

 demned by all the bed fnrgeor.s, thefe uapleafant confe- 

 quences are rendered much lefs frequent than in former days. 



Trepanning, in Sheep, the operation of extrafting 

 the bags or cyfls that contain a watery fluid from the 

 heads of thefe animals, wliich are the caufe of difeafe. See 

 Sturdy. 



TREPASSER's Bay, or Trepnjt Bay, in Geography, 

 a bay on the fouth coaft of Newfoundland. N. lat. 46° 50'. 

 W.long. 53°. 



TREPEIA, a town of Servia; 5 miles N.E. of 

 Novibafar. 



TREPHINE, in Surgery. The operation of trepanning 

 is now frequently called the operation of trephining, from 

 it3 being generally performed in this country with a trephine, 

 which is a more modern inftrument than the trepan. The 

 trephine confifts of a iimple cylindrical faw, with a handle 

 placed tranfverfely, like that of a gimblet ; and from the 

 centre of the circle, which the teeth of the faw defcribe, a 

 fliarp httle perforator projefts, named the centre-pin. 

 The upper part of the centre-pin is made to fcrew into a 

 correfponding hole at the infide of the top of the faw, and is 

 capable of being taken out or put in at the furgeon's option, 

 by means of a little key for the purpofe. Its ufe is to fix 

 and fteady the trephine, when the inllrumcnt firft begins 

 to work, that is, before the teeth of the faw have made a 

 fuflicient circular groove, in which they can feciu-ely move. 

 But as foon as an adequate groove is formed, the centre-piu 

 muft always be taken out ; becaufe it is now unneceflary, 

 and, if not removed, it would not only retard the progrefs 

 of the operation, but inevitably penetrate the dura mater 

 and brain, when the teeth of the faw had cut to a certain 

 depth through the cranium. Some trephines contain centre- 

 pins, which are contrived to Aide up or down, and to admit 

 of being, fixed in either fituation, by turning a little fcrew. 

 This method feems to us both ingenious and convenient. 



The cylindrical part of the trephine is often termed the 

 iroiuti of the inftrument. The furgeon {hould always have 

 at leaft two or three cylindrical faws cf various fizes ; for it 

 is a commendable rule never to faw away any more of the 

 cranium, or indeed of any other bone, than is abfolutely re- 

 quifite for the accompli(hment of fome affignable objeCl. 

 There is no occafion, however, for having more than one 

 handle, which may be made to fit any of the faws. 



The trepan is worked in the manner of a wimble, the 

 inftrument turning round and round upon its own axis ; but 

 the trephine only performs femicircular movements, which 

 the furgeon imparts to it by the pronation and fupinaiion of 

 his hand. As its teeth are arranged perpendicularly, they 

 cut whether the inftrument is turned from the left to the 

 right, or from the right to the left. 



Certainly cafes do frequently prefent themfelves, in which 

 trephining is abfolutely neceflary ; and yet there is no oc- 

 cafion for removing a complete circular portion of the 

 cranium j the taking away of a piece of fmaller fize, and 



difierent {hape, would fometimes be much more advan- 

 tageous. A very good inftrument for effe&ng this pur- 

 pofe is a common trepKinr, terminating only in a femicir- 

 cular faw, inftead of a circular one. With this the furgeon 

 can cut acrofs the bafe of certain deprefled portions of 

 bone, and tiike them away, without any occafion for re- 

 moving alfo a circle of the cranium. 



The faws, however, whicli Mr. Hey has defcribed, (hould 

 conftantly be kept in every cafe of trephining inftruments. 

 This praftical writer remarks, that " the purpofes for 

 which any portion of the cranium is removed, are, to enable 

 the furgeon to extraft broken fragments of bone, to elevate 

 what is depreffed, and to afford a proper ifl"ue to blood or 

 matter that is, or may be confined, &c. 



" When a broken frnj^ment of bone is driven beneath the 

 found contiguous part of the cranium, it frequently happens 

 that the extraftion cannot be executed wnthout removing 

 fome of the unbroken part under which the fragment is 

 deprefted. This might generally be effeded with very little 

 lofs of found bone, if a narrow portion of that which lies 

 over the broken fragment could be removed. But fuch a 

 portion cannot be removed by the trephine. This inftru- 

 ment can only faw out a circular piece. And as, in execut- 

 ing this, the central pin of the faw muft be placed upon 

 the uninjured bone, it is evident that a portion of the found 

 bone, greater than half the area of the trephine, muft be 

 removed at every operation. When the broken and de- 

 prefled fragment is large, a repeated application of the 

 trephine is often neceflary, and a great dellruttion of found 

 bone muft be the confequence. 



" When the injury confifts merely of a fifl^are with de- 

 preflion, a fmall enlargement of the filfure would enable the 

 furgeon to introduce the point of the elevator, fo as to raife 

 the deprefled bone. But a fmall enlargement of the fiflure 

 cannot be made with the trephine. When it is necefl'ary to 

 apply the elevator to diff^erent parts of the d*!prefled bone, 

 a great deal of the found cranium muft be removed, where 

 a very narrow aperture would have been fuflicient. 



" The fame reafoning will apply to the cafe of openings 

 made for the purpofe of giving a difcharge to extravafated 

 blood or matter. 



" If a faw could be contrived, which might be worked 

 with fafety in a ftraight, or gently curvilineal direftion, it 

 would be a great acquifition to the praftical furgeon. 

 Such a faw I can now wit!i confidence recommend, after a 

 trial of twenty years, during which time I have rarely ufed 

 the trephine in fraftures of the fl<ull. Its ufe has been 

 adopted by my colleagues at the General Infirmary in Leeds ; 

 and will be adopted, I hope, by every furgeon who has 

 once made trial of it." Mr. Hey next informs us, that the 

 inftrument was firft fliewn to him by Dr. Cockell of Ponte- 

 fraft ; but that there is a faw, formed on the fame principle, 

 in Scultetus's Armamentai-ium Chirurgicum. The faws 

 alluded to are very ftiort ones, fixed at the end of a longifh 

 ftraight handle ; their edges are made either ftraight, or 

 femicircular. The latter conftruftion qualifies the inftru- 

 ment for cutting in a curvilineal direction, which is often 

 proper. The edge of the faw (hould always be made a 

 Httle thicker than the reft of the blade, by which means it 

 will work in the groove, which is cut, with more facility. 



Saws made on the principle juft defcribed, are alio of 

 infinite ufe in cutting away difeafed portions of other bones, 

 befides the ikull, exoftofes, &c. In cafes of necrofis, when 

 a dead part of a bone is quite wedged in the fubftance of 

 the furrounding new bony matter, Mr. Hey's laws may 

 often be advantageoufly employed for cutting away the 

 parts which mechanically prevent the detachment of the 



dead 



