VALENTIN S KNIFE. 



201 



covered with white wax, and then immerse it in the water- 

 trough ; the more delicate the structure, the sooner after 

 death should it be examined, especially animal tissues. 

 With some vegetable structures, the dissection should be 

 carried on under water. The sepa- 

 ration of the woody and vascular 

 tissues, and the spiral vessels, is best 

 effected by maceration and tearing 

 with fine needles. 



Valentin's Knife. For making fine 

 sections of large substances, or those 

 soft in structure, such as the liver, 

 spleen, kidney, &c., the double-bladed 

 knife, the invention of Professor 

 Valentin, may be used with advan- 

 tage. An improved construction of 

 this knife, by the late Mr. John 

 Quekett, is represented in fig. 129. 1 

 It consists of two blades, one of 

 which is prolonged by a flat piece of 

 steel to form a handle, and having 

 two pieces of wood riveted to it, for 

 the purpose of its being held more 

 steadily ; to this blade another one 

 is attached by a screw ; this last is 

 also lengthened by a shorter piece of 

 steel, and both it and the preceding 

 have slots cut out in them exactly 

 opposite to each other, up and down 

 which slot a rivet with two heads is 

 made to slide, for the purpose either 

 of allowing the blades to be widely 

 separated or brought so closely to- 

 gether as to touch. One head of this 

 rivet, being smaller than the hole in 

 the end of the slot, can be drawn Fi s- 129. 



through it ; so that the blade seen in the front of the figure 

 may be turned away from the other in order to be sharpened, 



(1) Another fcim of this instrument is constructed by Mr. Matthews the 

 blades being made with a convex instead of a straight edge, 'their distances from 

 each other being regulated by a milled-head screw, and their separation for 

 cleaning being more readily accomplished. 



1 1 



