DISSECTING INSTRUMENTS. 345 



wedge open certain closed parts without the risk of cutting 

 them. Scissors in which the blades are curved, as shown at 

 D or at E in fig. 227, are also very necessary. 



Cutting Forceps. — This instrument, the invention of Mr. 

 William Valentine, is represented by C, fig. 227; the sides are 

 rivetted at the end, as those of the ordinary forceps, but the 

 cutting part consists of two scissor-shaped blades, which over- 

 lap each other, and are prevented from crossing over too far 

 by a small steel pin, the blades are bent at an angle with the 

 sides, and by this means the instrument can be very conve- 

 niently employed for dissecting under a lens of half-an-inch 

 focus. An instrument constructed somewhat after the same 

 principle as the above, is known as the Microtome, the inven- 

 tion of M. Straus Durckheim ; it consists of two sides, like 

 a pair of dissecting forceps, but each terminated by a scissor- 

 shaped blade, arranged so that its cutting edge is perpendicular 

 to the broad surface of the side; in order to prevent the blades 

 from opening too wide, a screw with a fly nut is attached to 

 one blade, and the other moves freely upon it ; the screw is 

 also provided with another nut situated between the blades, 

 the latter may be adjusted so as to prevent the blades from 

 being closed beyond a certain point, whilst the former serves 

 to regulate the space that the blades may be kept open by the 

 spring. The sides are not rivetted together as in the dissect- 

 ing forceps, but are united by a hinge-joint, in order that they 

 may be separated for the pui-pose of sharpening the blades. 

 Spring Scissors. — These are represented by fig. 229, and 



Fig. 229. 



consist of a pair of very small scissors, the blades of which are 

 kept open by a spring, a. One of the handles is attached to a 



