[ 40 ° ] 
for the PafTage of the Wire. Without this Solidity 
and this NarrOwnefs of the PafTage of the Wire, the 
Catheter would not be firm ; and the Wire itfelf,. 
liable to waver, would not run true, but would im- 
part its W eaknefs, or Want of juftnefs, to the move- 
able Piece C, which is the Guide of this Operation. 
This Body, G , is folder’d to the Piece I) at H, 
making it enter fquare into the faid Piece * D , till it 
meets the Slider B, which I fuppofe intirely within 
the Piece F). The Rings are very large and ftrong, 
for the Conveniency of ufing it. 
This Catheter is made of Silver, from the Rings 
inclufive to F: AH the reft, together v/ith the Wire, 
ought to be of the hardeft Gold; becaufe it is on 
this End of the Catheter that the greateft Strefs is 
laid; and Silver has not Firmnefs enough to refift the 
Efforts that thefe Pieces muft fuftain. And particu- 
lar Care muft be taken, that all the Angles and Pro- 
minences be render'd very fmooth. 
I enter into thefe Details of the Make of the In- 
ftrument, becaufe I have learn’d, to my Coft, that the 
Workmen do not think of them. 
Fig-. 2. (hews the whole Mechanifm of this Cathe - 
ter> by reprefenting it open, and fuch as it is in the 
Bladder while the Incifion is making. 
The Piece B , of Fig. i. is here funk in its Sheath 
T); whereby the fmall Style or Wire is thruft to- 
wards the crooked End of the Catheter , and, at the 
fame time, pufhes the End b of the fmall moveable 
Piece C towards this fame Parr. The Catheter being 
thus open in the Bladder, when the Operator draws 
the Inftrumcnt towards him, it is Popp’d by the Neck 
of this Organ, at the Place mark’d dd $ and then the 
Angle 
