32 Introductory Biology 



Until the end of the nineteenth century the making of complete micro- 

 scopes was largely done by individuals who made one microscope at a 

 time. The metal parts were made by hand and the lenses ground and 

 polished with rather simple equipment. Increasing demands for more 

 microscopes suggested to manufacturers that specialists (scientists, design- 

 ers, engineers, specialized workers, etc.) must be trained and standards 

 set and that microscopes must be built on an assembly line basis. The 



EYEPIECE 



COARSE ADJUSTMENT 



BODY TUBE 



DUAL-CONE 



NOSEPIECE 



OBJECTIVES 



COVER GLASS 

 AND SLIDE 



CONDENSER 



LOWER IRIS 

 DIAPHRAGM 



FORK-TYPE 

 SUBSTAGE 

 MOUNTING 



MIRROR 



MICROMETER-TYPE 

 FINE ADJUSTMENT 



STAGE CLIP 



STAGE 





ARM 



NCLINATION 

 JOINT 



SUBSTAGE 

 ADJUSTMENT 



PILLAR 



-BASE 



Fig, 5. — Modern microscope with more important parts labeled. (Courtesy of 

 Spencer Lens Co. [Scientific Instrument Division of American Optical Co.]) 



twentieth century has seen many improvements in the manufacture and 

 usefulness of the various types of microscopes (Figs. 5 and 6). Some of 

 the more recent improvements include ultramicroscopes, ultraviolet 

 microscopy, dark-field microscopy, phase microscopy, and electron mi- 

 croscopy. 



When particles too small to be seen with a microscope under ordinary 

 conditions are illuminated by a strong beam of light parallel to the sur- 



