ON DRAWING. 3 
IV.—ON DRAWING. 
It is absolutely essential to draw your dissections, and this 
must on no account be omitted. Keep a separate book for 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 drawing systematically : 
1. Always make your drawing to scale, 2.¢., either the exact 
size of the natural object, or half or double or treble that size 
as the case may be. 
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, Always name the several parts shown in your drawing, 
and mark also the scale adopted. Thus, if your drawing be 
of the natural size mark it thus— x1; if it be double the size 
of the object mark it x 2; if half the size, x 4, and so on. 
5. Coloured pencils are very useful, and water-colour paints 
still better. Always keep certain colours for particular organs 
or tissues ; ¢.g., when drawing the skeleton colour the cartilage 
blue, the cartilage bones yellow, and the membrane bones either 
red or white ; when drawing the bloodvessels colour the arteries 
red and the veins blue. 
V.—THE USE OF THE MICROSCOPE. 
The microscope consists essentially of a stand and a body, the 
Jatter of which bears at each end the lenses by which the magni- 
fying power is obtained. 
The stand is an upright pillar, 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 
perforated in the middle by a hole, the size of which can be 
varied by means of diaphragms. Through this hole light is 
directed on the object to be examined by means of a mirror 
