THE MICROSCOPE 



53 



nence to one part of the specimen and repress others. 

 It is difficult to combine in one photograph structures 

 found in different fields. Mechanical accessories for 

 delineation of miscroscopic images are far more useful 

 than the microphoto- 

 graphic apparatus. 

 The essential parts of 

 the mechanical appa- 

 ratus are a prism and 

 a mirror so placed that 

 the image produced by 

 the ocular will be 

 reflected upon a draw- 

 ing surface. The re- 

 flecting device is so 

 constructed that the 

 worker may observe 

 the specimen and at 

 the same time see the 

 drawing surface. The 

 apparatus is termed a 

 camera ludda and is 

 more carefully de- 

 scribed hi a subsequent 

 chapter. With the 

 camera lucida one can 

 obtain drawings in 



which relative pro- FIG. 26. Microphotographic Apparatus. 



. . T (Bausch & Lomb.) 



portions are preserved, 



may combine in one drawing objects seen in different 



fields and may emphasize certain structures and ignore 



others. 



Free-hand drawing of microscopic images requires 



