DISSECTING INSTRUMENTS. 



347 



making long incisions in larger animals, and C for both 

 purposes, and for transverse sections of soft parts as well. In 

 the absence of these, the scalpels employed in the medical 

 schools may be used; generally speaking, however, they are 

 far too large for microscopical dissection ; the small instru- 

 ments contrived for operations on the eye will be found much 

 more suitable, and a case of the latter will be a good substi- 

 tute for the greater part of the instruments above described. 



Valentin's Knife. — One of the most frequent operations in 

 microscopical investigations is the making of fine sections; for 

 this purpose, the scalpels before noticed, or a 

 razor, may be employed; but for large sub- 

 stances that are soft, like the liver, spleen, and 

 kidney, the double-bladed knife, the invention 

 of Professor Valentin, may be used with ad- 

 vantage. This, as represented by A, fig. 231, 

 consists of two double-edged blades, one of 

 which is prolonged by a flat piece of steel to 

 form a handle, and has two pieces of wood 

 rivetted to it for the purpose of its being 

 held more steadily to this blade ; another is 

 attached by a screw ; this last is also length- 

 ened by a shorter piece of steel, and both it 

 and the preceding have shts cut out in them 

 exactly opposite to each other, up and down 

 which a rivet, a, with two heads, is made to 

 slide, for the purpose either of allowing the 

 blades to be widely separated or brought so 

 close together as to touch ; one head of this 

 rivet is smaller than the hole in the end of the 

 slit, and can be drawn through it so that the 

 blade seen in the front of the figure may be 

 turned away from the other in order to be 

 Fig. 231. sharpened or to allow of the section made by 

 it being taken away from between the blades. The blades 

 are constructed after the plan of a double-edged scalpel, but 

 their opposed surfaces are either flat or very slightly concave, 

 so that they may fit accurately to each other, which is effected 



