22 GENERAL BIOLOGY 



fully and note where the cut may be made to expose the part 

 wanted with the least injury to the surrounding parts. Do 

 not grasp nerves or bloodvessels with the forceps, but hold 

 the tissue at one side of them. Do not allow scraps to 

 accumulate on the specimen; with a pipette wash away 

 the debris which gathers on the specimen under water, and 

 change the water frequently. 



Instruments must be kept clean and sharp to accomplish 

 the best results, therefore do not use scissors or scalpel to 

 cut hard objects and do not allow the instruments to be- 

 come rusty. 



Clean and dry the instruments, after using, and smear 

 them with a little oil or vaseline. 



The scissors are used almost exclusively when cutting is 

 to be done. Each blade of the scissors holds the object for 

 the other blade, whereas the scalpel tends to push out of 

 the way the object to be cut, and also often leads to the 

 cutting of underlying tissues that should not be injured. 

 While cutting with one hand, whether with the scissors or 

 scalpel, always use the forceps in the other to steady the 

 object and to hold the edge of the cut. 



The Microscope 



Since the compound microscope is the instrument most 

 indispensable to the biological student some knowledge of 

 its construction and manipulation should precede its im- 

 mediate application to the work in which it is used. The 

 following study of its parts and their relations may there- 

 fore be made in the order indicated. 



1. Parts, (a) The base, a heavy support bearing (6) the 

 column to which is fastened (c) the stage, a horizontal sup- 

 port for objects to be examined. In the center of the stage 



