DISSECTING OBJECTS. 



119 



to a piece of wood, b ; the other is curved as at c, in order 

 to be pressed upon by the thumb or forefinger in the act of 

 cutting. 



The Microtome of M. Straus-Durekheim is constructed on a 

 similar principle, but more simple in form. Its appearance is 

 somewhat like the common shears, used for shearing sheep; 

 the cutting blades being kept apart by their union in the handle, 

 the distance being regulated by a screw and nut. By pressing 

 with the fingers upon the Microtome it will close, and open 

 when they are removed. The length of the cutting blades is 

 l^inch. 



The ordinary scalpels or knives are usually too large for all 

 purposes ; those, however, which are used in operations on the 

 eye will be of service. 



For making fine sections, a scalpel or a razor may be em- 

 ployed, but for soft substances, as the liver, spleen, and kid- 



ney, a knife with two parallel blades, called Valentin's Knife, 

 Fig. 33, may be used with advantage. Dissecting needles 

 may be straight or curved. One of the latter fixed in a pro- 



Fig. 34. 



per handle, is represented in Fig. 34. These are very service- 

 able instruments for separating or tearing asunder delicate 

 tissues. 



