22. HISTOLOGY OF MEDICINAL PLANTS 
pinion for moving the slide to left or right, and another rack and 
pinion for moving the slide forward and backward. 
CAMERA LUCIDA 
The camera lucida is an optical mechanical device for aiding 
the worker in making drawings of microscopic objects. The 
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Fic. 27.—Camera Lucida 
instrument is particularly necessary in research work where it 
is desirable to reproduce an object in all its details. In fact, all 
reproductions illustrating original work should be made by 
means of the camera lucida or by microphotography. 
Agreat many different types of camera lucidas or drawing 
apparatus are obtainable, varying from simple-inexpensive to 
complex-expensive forms. Figs. 26, 27, and 28 show simple 
and complex forms. 
as 
