l8 HINTS TO STUDENTS ON PRACTICAL WORK 



you see with the naked eye. The microscope is merely 

 an instrument which extends the power of the eye 

 so that it can detect the fine details of structure. 



(6) Never put on the high power unless the object 

 is covered with a coverslip, or you will be almost certain 

 to get the mounting medium on to the lens of the 

 objective. 



(7) Never focus the high power carelessly, or you 

 will jam it on to the slide, spoil the object, and very 

 likely injure the objective. When you have put on 

 the high power, note its distance from the coverslip 

 by looking from the side (you will soon learn to judge 

 about the distance at which it is in focus). Correct 

 the distance with the coarse adjustment carefully, till 

 you judge it is about right, and then look through the 

 microscope and focus accurately with the fine adjust- 

 ment. 



Observation and Drawing of Structure. 



Careful observation, followed by accurate drawing 

 of the structures of plants and animals, whether seen 

 with the naked eye, with a hand lens or under the 

 microscope, is an indispensable means of acquiring a 

 sound first-hand knowledge of biology. It is also one of 

 the best methods of training the mind to form and retain 

 clear mental pictures, and this power is most valuable 

 in almost every occupation of life, most notably in the 

 everyday work of the medical man. It is therefore of 

 great importance that the student should seriously 

 bend his mind from the start to learning how to 

 represent what he sees in drawings and diagrams. 



The power of making good representations on paper 

 of what one sees varies very much in different people 

 some find it comparatively easy, others very difficult. 



