394 Proceedings of the Royal Institution, 



gnle." Tilfe invetiiiofi of tlie JireWbtis in^trumeTits we believe to rest 

 with Gruithiuseli, Civiale, and Le Roy; l)ut they have each been 

 hnproved by Baron Hiierteloup in design and construction. The 

 following, which are well fitted to seize and destroy stones exceeding 

 fourteen lines in diameter, and those which are flat, we are informed 

 belong solely to the latter. 



It is a fact well known, that when the stone is large, the bladder 

 in general is small ; not only relatively, but absolutely smaller than 

 when the stone is of moderate dimensions ; and, furthermore, that 

 the bladder contracts frequently upon the stone, and assumes a pre- 

 ternatural muscularity, the inner surface having not only a rugose, 

 but a columnar character. This, of course, will prevent that viscuS 

 from being freely distended by injection, will keep the stone nearer 

 the neck of the bladder, and might interfere with the fully extended 

 tentacula of the three-branched forceps. The larger the calculus i^ 

 the more numerous of course must be the perforations made in it 

 before its substance will break down, and even with the excentric or 

 virgule drills, the process would still be tedious, although much more 

 speedy than if simple perforations alone were made. The irregula- 

 rity of stones likewise gives rise to difficulty in their apprehension 

 and firm retention, as it seldom happens that all the claws, moving 

 simultaneously, close upon the calculus, especially if it be a large 

 one ; so that when pressed upon by the drill, it is apt to slip or to 

 elude the grasp. 



Furthermore, that form of the three-branched forceps previously 

 described, the whole of the tentacula of which are in union, and 

 of necessity move together, can never, at its utmost stretch, project 

 a span of more than one-third of its circumference ; and even this 

 diminishes rapidly towards the canula, there being no means of 

 keeping the springs at any greater width from each other. '' 



To overcome these difficulties all the instruments have been modi- 

 fied, and others added, by Baron Heurteloup, who designates this 

 improved apparatus, which is fitted to destroy stones twenty-four 

 lines in diameter, " Evideur h forceps,*' (excavator with forceps j) 

 and it consists of several parts, which may be briefly thus described : 

 The straight cantila, instead of being a simple cylinder, as in the 

 other apparatus, contains fixed within it another tube nearly equal to 



