rNTEODUOTION XXI 



tion of parts. Shading is seldom desirable. Draw every- 

 thing to scale, and mark on the drawing the scale adopted. 

 Always sketch in the outline faintly at first, then fill in the 

 details. When the specimen is bilaterally symmetrical, draw 

 a faint line to represent the median line, sketch the outline 

 of the left, then of the right side, and fill in the details. 

 Make every drawing large enough to show all of the parts 

 plainly. Name every part or organ in every drawing. It 

 adds much to the appearance and value of the drawings if 

 they be colored with water-colors, using the dull tints for 

 the larger and the bright colors for the small organs. In a 

 set of drawings of the same specimen always use one color 

 for the same system or organ. Indicate arteries in red, 

 veins in blue, and other parts in their natural colors. 

 Drawings must not be made too sm,all 



Using the Microscope 



1. Take the instrument from the case together with the 

 eye-piece and objective to be used, then close the case and 

 set it aside out of the way. 



2. Examine every part of the instrument to be sure that 

 it is clean. Wipe oflE the dust by brushing lightly with a 

 sofi clean cloth. 



3. If there be anything but dust on the objective, wipe 

 the latter with a soft, moist cloth, then dry immediately 

 with a soft cloth. If this fail to remove the dirt, take the 

 objective to the instructor. Do not use chamois skin or 

 soiled cloths of any kind. A worn linen or silk handker- 

 chief, kept perfectly clean and free from dust, is as good as 

 anything that can be found to clean the microscope. 



4. Put in the eye-piece ; screw on the objective. 



5. Incline the tube at a convenient angle. 



6. Turn the tube down to about one fourth of an inch 

 from the stage. £e exceedingly careful to avoid contact 

 of the front lens with the stage or with anything upon 

 it. 



