for Destroying a Stone in the Bladder, 23 



E, Fig. 3y which exactly fills up the interval between the tubes, 

 and in which there are four holes for the passage of the springs, 

 which have a small bit at one end turned down to prevent their 

 being drawn through, and the temper of the steel is lowered, so as 

 to admit of their being freely bent : they are passed from within 

 outwards through two of the knobs, and brought back by the 

 others, so as to form two loops, with which it is proposed to fix the 

 stone ; they cross each other and pass through a ring H, which 

 rises and falls as you increase or diminish the bow of the springs. 

 The other ends pass down in the grooves before-mentioned, and 

 are fixed in the collar I. Fig. 1, by the screws K K, and by means 

 of which they are slid up and down, either together or separately ; 

 L is a screw which fixes the collar when the stone is caught by the 

 loops ; m m is an elastic wire wound round the part of the inner tube, 

 which is not enclosed in the canula, and serves to prevent the 

 springs from bending outwards when pushed up ; N N is a drill ; 

 the part of which that works in the curve is constructed in the 

 same manner as the flexible part of the inner tube, but the metal 

 is thicker, to give strength to bear the pressure necessary to per- 

 forate a stone ; the other end is made of pinion wire, which passes 

 through corresponding grooves in the pulley O, which enables it 

 to be pushed forward at the same time that it is turned ; the ex- 

 tremity works like a swivel in the socket P, attached to the ring 

 R. The drill head takes off, that different sked ones may be 

 used ; they are made to cut one way only, as the flexible part, 

 though quite firm enough when turned in one direction, in the op- 

 posite would have a tendency to unwind, if.it met with much re- 

 sistance. 



To make use of this instrument, the canula, with the stilet in 

 it, is passed ; the latter is then withdrawn, and the second tube, 

 with the watch springs attached, is pushed through it, and the 

 end fixed in a hole in the upright S ; the collar is then slid up, 

 and the springs bow out in the manner represented in the plate : 

 the springs may be worked up and down till the calculus is 

 caught ; it is then fixed by means of the screw in the collar, and 

 in this way can be retained more firmly than with any forceps ; by 



