radiation used to illuminate the specimen and the physical properties of 

 the specimen. When the image is formed by visible light as in the ordi- 

 nary light microscope, it can be examined directly with the eye or re- 



eyep iece 



stage 



rack and 

 pinion 



mirror 



Figure 11-8. Drawing of a Compound Microscope with its Principle 

 Parts Labeled. (From Ham, A. W., 1957. "Histology;" 3rd ed., J. B. Lippin- 

 cott Co., Philadelphia, Pa., Fig. 14, p. 19.) 



corded on a photographic film. Images formed by shorter wavelength 

 radiations, such as the ultraviolet, to which the eye is not sensitive must 

 be examined by means of a recording device such as a photoelectric cell 

 or photographic plate. 



The physical properties of the specimen most commonly exploited in 



224 / CHAPTER 11 



