[ rar ] 
in the fame form for a feries of years; and confidering that this 
operation muft have been often neceflary, from the accidents 
which have never ceafed to occur, it is a matter of fome furprife 
that the inconveniencies attending the two inftruments now 
generally ufed, namely, the trepan and the trephine, fo called, 
have not been in fome meafure removed. The only attempt that 
has fallen under my obfervation was by Mr. John Douglas, a 
figure of whofe inftrument may be feen in the Edinburgh Medi- 
cal Effays *, and thus defcribed, “ Two brafs plates kept together 
“ by four pillars of brafs, with a handle moving a tooth wheel, 
“« which turns a pinion to which the focket for receiving a com- 
“ mon faw-head of a trepan is fixed.’ This defcription is fol- 
lowed by a remark, “ That the faw will be turned more equally 
“ with this inftrument than with the hand alone; but whether 
“ the rattling and trembling which the wheels make are fuflicient 
“ to counterbalance this advantage, I fhall not determine.” By 
this we may fuppofe it has never been introduced into praétice. 
To the above objection might be added, the chance that a ma- 
chine of the conftruction now defcribed might be liable eafily to 
be put out of order. Though the ingenuity of the invention 
muft be acknowledged, and no doubt Mr. Douglas was well fatis- 
fied that fomething to render the operation of trepanning more 
expeditious, fafe and eafy, was wanting. 
Every Surgeon will admit that both the trepan and trephine 
are attended with inconveniencies; as a° proof of this, I need 
Vou. IV. R only 
* Vol. V. Table iv. Fig. 6. page 374. 
