396 Proceedings of the Royal Institution. 



when rotated by means of the bow as before, excavates the stone, 

 leaving nothing but a thin shell formed of its outer layers, which the 

 vvithcli:aw?vl of the branches of the forceps will usually be sufficiecit 

 to ,9f^sjbi: should it, however, resist their force, the indicator may be 

 used as a " .percusseur," and one or two strokes of the simple st^el 

 rod upon the shell will inevitably reduce it to fragments. , ^^ > , 



Such is the economy of the excavating apparatus, which, for the 

 destruction of large round stones, is incomparably the best instru- 

 ment yet invented : but the seizure and destruction of flat stones, ox 

 the flattened shell-like fragments of larger calculi, have presented 

 many difficulties to the operating lithotritist. 



The " shell-breaker," or brise-coque, would seem to obviate these. 

 It lias been said to be merely an unprovement on the brise-pierre of 

 Amusat: inti-uth, the chief difference between them is, that, although 

 both are ingenious instruments, the one is hig;hly useful, the other 

 inapplicable in practice. 



The shell-breaker both seizes and crushes the calculi or fragments 

 without the assistance of drill or perforation. Hence, it is necessa- 

 rily made very powerful in its branches, and to allow such strength 

 in its construction, without increasing too much the size of the tube, 

 it consists but of two branches, which entirely fill up the canula, and 

 are terminated by strong roughened jaws, which open by a spring 

 placed between them, and receive the calculus, when detruded from 

 the canula, and, closing in their retreat, crush the hardest stone or 

 fragment between their hawk-bill ends. Motion is communicated to 

 tliese branches by a double rack and two wheels contained within the 

 handle, the inward and outward progress being commanded by a 

 sprinar catch which resrulates the rack. 



It has been usual to operate on an ordinary bed or couch, and to 

 fix the lithotritic instruments in a spring vice held by an assistant, 

 while the surgeon completed the perforation of the calculus by the 

 drill and bow ; but when a much more powerful means, viz. the ex- 

 cavator, is employed, it becomes necessary that the instruments 

 should be held more steadily; and for this purpose Baron Huerte- 

 loup has constructed a very ingenious bed, the " lit rectangle," to the 

 front of wliich there is a moveable vice attached, and which can.^lso 

 be lowered as a whole, by moveable liind legs, so as to form an in- 



