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 



FIG. 27. 



'amera Lucicia 



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. 



A great 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. 



