Proceedings of the Royal Institution. 395 



itself in length, wliich is four-sided, so that the chief channel is sub- 

 divided into five compartments, a square central one, and four cir- 

 cumferential passages, through each of wliich latter passes one 

 branch of the forceps, which here consists of four instead of three 

 tentacula. Three of the branches are terminated at their vesical ex- 

 tremes by simple curves, the fourth and longest by a grooved knob, 

 wliich closes in the whole, and facilitates the introduction. The four 

 branches of the forceps being separate from each other, and sliding 

 in separate grooves, may hence, by knobs fixed to their manual ends, 

 be each moved independently of the other, or by a case which in- 

 closes the knobs of all, be made to act simultaneously; thus com- 

 bining, with all the advantages of the common forceps, the very 

 important privilege of separate, and more or less conjoint action. 

 The four-branched instrument, by the withdrawal of one of its ten- 

 tacles, may also be converted into a superior three-branched forceps, 

 as the span of its branches will be the diagonal of its square, instead 

 of the mere base of an equilateral triangle, as in the former case ; 

 so that stones of much greater magnitude can be seized, and with 

 much less extension of the instrument : furthermore, the knobbed 

 tentacle, when withdrawn, will still more widen the grasp of the 

 other three, and keep them fully and firmly apart. The separate 

 motions of the tentacles will also allow each to be separately pulled 

 toti, so that every one can be firmly acting on the stone, a very im- 

 portant circumstance. Tlie knobbed tentacle may, subsequently to 

 the prehension of the stone, be detruded, and it will also close upon 

 ^; and when all four branches act, the retention is the most firm that 

 can be conceived. Through the central cavity the subsidiary instru- 

 ments are introduced ; these consist of a simple steel rod, called the 

 y Indicator," and a very delicate three-branched " assistant forceps," 

 (pince servante,) designed to bring the calculus within the grasp of 

 the larger and stronger instrument, should it not, in the first instance, 

 be easily apprehended. The instruments destined to destroy the stone 

 consist of a pointed steel rod, the " perforator," which, rotated by a 

 common drill bow, makes a hole in the stone ; and the " excavator," 

 (^vi4eur) which is a somewhat similar rod, the end of which is a 

 V^ powerful rasp or file, which can be inclined, by means of a 

 B6te#, to any anglfe the size of the calculus may require, and whidi, 



