OPENING THE TRACHEA BY DILATATION. 289 
shoulder of the blade until the wings or arms are compressed 
towards each other, when the trocar becomes immediately 
disengaged, and can be instantly withdrawn. 
The mode in which I propose to use it is this : A suitable 
incision having been first made through the integument in 
the mesial line, the operator takes the instrument in his 
right hand, and then, by directing it backwards and down- 
wards, in a direction very much indicated by its own curve, 
introduces it, between two of the rings, into the trachea. 
Then compressing the little curved arms with his left hand, 
he at once disengages and withdraws the trocar, and has now 
his right hand free to turn the revolving nut, which will keep 
the sides of the canula in any degree of dilatation which may 
be required. 
The instrument now’ submitted is extremely rude, and 
only meant to exemplify the principle of that w^hich is pro- 
posed for the consideration of the profession. It will be 
seen that I have been even obliged to construct the divari- 
cating springs, on wdiich the perfect working of the instru- 
ment so much depends, of bits of w halebone, not being able 
to meet with a smith here who could properly attach them 
for me. I hope, then, that all due allowance wdll be made 
for the imperfections in the finish and construction. The 
rationale of the device will, I hope, be understood and appre- 
ciated from this model. 
The trocar blade,' if the instrument be skilfully con- 
structed, will without difficulty cut its way into the trachea, 
while the “tactus eruditus” will at once admonish the 
surgeon when he has arrived there. Should an irregular 
arterial branch cross the site of his operation, it will roll 
aside from the touch of such an instrument and escape 
division, w r hile the tapering form of the instrument not only 
favours the dilatation of the structures to be traversed, but, 
by its wedge-like action, is well calculated to prevent 
haemorrhage, should a vein be opened, while the operator 
gains this additional advantage, that he fixes in the trachea 
his canula by one and the same act which opens the passage. 
Mr. Smiley said he had used a pointed trocar on three 
different occasions, and gave it as his opinion that the in- 
strument forwarded by Dr. Johnson was calculated to be of 
great service to the profession ; though, at the same time, he 
did not think it w ould supersede the necessity of making a 
larger opening into the trachea. Where there w r as haemor- 
rhage, or any urgent necessity for opening the trachea, they 
might insert the instrument, and in the course of a few hours 
afterwards an opportunity would be afforded for enlarging 
