THE USE OF THE MICROSCOPE 3 



your drawings, and draw every dissection you make. Do not be 

 discouraged if you find it difficult at first : you will never 

 regret time spent on it. 



The following rules will be useful to those who have not 

 learnt to draw systematically : 



1. Make your drawing to scale, i.e., either the exact size of 

 the natural object, or half or double or treble that size, as the 

 case may be, remembering always that a drawing can hardly be 

 made too large. 



2. In commencing a drawing, first determine by careful 

 measurement the positions of the principal points, and sketch 

 in lightly the whole outline before finishing any one part. 



3. If the object you are drawing is bilaterally symmetrical, 

 draw a faint line down the middle of your paper, and sketch in 

 the left-hand half first ; by measuring from your median line 

 it will be very easy to make the two halves symmetrical. 



4. Name on your drawing the several parts shown, and mark 

 also the scale adopted. If your drawing be of the natural size 

 mark it thus — x 1 ; if it be double the size of the object mark 

 it X 2 ; if half the size, x |, and so on. 



5. Draw on one side of the page only : and write an explana- 

 tion of your drawing on the opposite page. 



6. Always make your drawing in pencil first, since much 

 clearer outlines can be obtained with pencil than with chalk, 

 but for complicated drawings coloured pencils are very useful, 

 and water-colour paints still better. Keep certain colours for 

 particular organs or tissues ; e.g., when drawing the skeleton 

 colour the cartilage blue, the cartilage bones yellow, and the 

 membrane bones either red or white ; when drawing the blood- 

 vessels colour the arteries red and the veins blue. 



7. Draw only what you see. 



IV.— THE USE OF THE MICROSCOPE. 



The microscope consists essentially of a stand and a body, the 

 latter of which bears at its ends the lenses by which the magni- 

 fying power is obtained. 



The stand is an upright piUar, the lower end of which is 

 attached to a heavy foot to ensure steadiness. A little way 

 above the foot the stand supports a horizontal plate — the stage 

 — on which the object to be examined is placed. The stage is 



