40 
A D ESCRIPTIOl^ OF ALL TFlE 
Setl. IX. 
by proper dreffings ; at the fame time keeping the joint at reft, and purfuing’ 
the antiphlogiftic courfe. 
» 
(B.) In the operation of the trepan, I have advifed that the cranium ftiould 
not be entirely cut with the faw, but that the operator fhould defift from faw- 
ing when the innermoft lamella becomes fo thin that it can be eafily broken 
off with a levator or forceps ; by which we not .only avoid the danger of the 
inftrument preffmg rudely on the brain, but alfo, in many cafes, the cutting 
of the dura mater, and admiffion of the air to the furface of the brain ; which, 
in experiments I made on half a dozen pigs near thirty years ago, I found in- 
creafed the danger confiderably. 
(C.) In the cafe of air effufed into the cavity of the pleura, for which, fofar 
back as 1758, 1 ventured to propofe the paracentefis of the thorax, I have ad- 
vifed that the operation ftiould be performed with a fmall trocar paffed cautioufty 
in a ftanting direction ; and, after withdrawing the ftilette, and letting out the 
effufed air, that a flexible canula, with a plug fitted to it, ftiould be introduced, 
in order to preferve an outlet to the air till the wound of the lungs be clofed ; 
and that, before withdrawing the canula, any air remaining in the pleura ftiall 
I 
be fucked out with a fyringe or elaftic bottle. And in 1769 a cafe occurred, 
in which, by my direction, that operation was performed nearly in this man- 
ner with relief and fuccefs (^t). 
Inftead of the cautious method above mentioned, Mr Hewfon (i/), and others 
following him, have propofed an incifion by a knife ; which I have found, even 
in experiments on found animals, generally proves fatal, from the violent de- 
gree of inflammation which tl^e free admiffion of the cold air creates. In one 
experiment on a pigj the inflammation from the admiffion of air by a fmall 
incifion 
{t) See an account of this cafe communicated by Mr Kellie, one of the furgeons prefent, to Dr 
Duncan, and publilhcd by him in his Medical Commentaries, Vol. II. p. 427. 
(?/) Med. Ohferv. London 1767, p. 396. 
