THE FROG 9 



of a honey-bee, and a light object such as some crystals of 

 salt or sugar. Observe the greater distinctness of the gen- 

 eral surface, and the loss of distinctness of the outline, as 

 compared with the results obtained by examining the same 

 objects by transmitted light. 



The student should accustom himself to making delicate 

 dissections under the dissecting lens; the object should be 

 completely covered with water in a small tray or Syracuse 

 watch glass placed on the dissecting stand. 



V. PRELIMINARY EXERCISE ON THE USE OF THE COM- 

 POUND MICROSCOPE. 



With the aid of an instructor, identify the following parts 

 of the microscope: Stage, diaphragm, mirror, tube, ocular 

 or eye-piece, low and high power objectives, coarse adjust- 

 ment, fine adjustment. 



Place the microscope in front of you close to the edge of 

 the table and adjust your chair to the proper height so that 

 by leaning forward you can look down through the tube 

 without discomfort. Better results can be secured if the 

 stage is kept level. 



Place a small transparent object, which will be furnished 

 mounted on a slide and covered with a cover glass, in the 

 center of the stage. The use of the clips for fastening the 

 object glass in place is, as a rule, to be avoided, since they 

 interfere with delicate manipulation of the slide. Adjust 

 the concave mirror and the diaphragm so that light passes 

 through the object. 



A. Use of the Low Power. With the low power ob- 

 jective in line with the tube, and the eye on a level with the 

 stage, turn the coarse adjusting screw so as to lower the 



