GENERAL BIOLOGY 



and make the drawings large enough so that all details can be 

 represented without confusion. 



2. To draw to scale : Place paper at base of microscope and 

 endeavor to trace outlines as seen with left eye while seeing point 

 of pencil at same time with right eye. The pencil point must appear 

 to coincide with the part of the object being drawn. Do not move 

 the eyes. 



IV. EXAMINATION OF COMMON OBJECTS. 



1. Mount a few fibres of wool, cotton, linen and silk in water 

 on different slides, cover with cover glasses and examine first un- 

 der a low power, then under a high one. How do the fibres differ ? 

 Sketch and label one of each under the lower power and then under 

 the high power of the microscope, drawing to scale. 



2. Examine a drop of emulsion (oil suspended in water) and 

 notice peculiar effects of refraction when lenses are focused upon 

 different portions of a drop. 



3. Examine bubbles of air in water. These may be obtained by 

 running water under a cover glass supported at one side by a bit 

 of paper and then tapping on the cover glass with a needle. What 

 differences can you see between these and oil drops ? 



[8] 



