296 PKACTICAL PHOTO-MICROGKAPHY 



Illuminant, Welsbach incandescent gas. 



Condenser, achromatic. 



No auxiliary condenser. 



Screen, saturated solution of auramine, 1 mm. thick. 



Camera -extension, 5 ft. 9 in. 



Plate, Imperial orthochromatic. 



Exposure, 4 minutes. 



Development, pyro-soda. 



The chief difficulty in photographing such a preparation 

 arises from the fact that the sections are seldom thin, and 

 therefore several planes have to be brought into approximate 

 focus at the same time. The only way of successfully dealing 

 with the matter is to reduce the aperture of the sub-stage 

 condenser as far as practicable without loss of definition. It 

 therefore results, as shown in this photograph, that no part 

 of the object is in what might be called critical focus, a 

 compromise having to be effected so that only moderately 

 good definition can be obtained. 



PLATE VI, FIG. 2. Bacillus pestis in Blood (Bubonic 

 Plague), x 750. 



Stain, methylene-blue. 



Objective, -^-inch oil-immersion, by C. Eeichert. 



Ocular, none. 



Illuminant, oil lamp. 



Condenser, Swift achromatic. 



No auxiliary condenser. 



Screen, filter-yellow-K, 1 mm. thick. 



Plate, Imperial orthochromatic. 



Exposure, 6 minutes. 



Development, pyro-soda. 



PLATE VI, FIG. 3. Bacillus tuberculosis. Giant Cell in 

 Lung, x 1000. 



Stain, Ziehl-Neelsen carbol-fuchsin and methylene-blue. 



Objective, ^-inch oil-immersion, by W. Watson & Sons. 



Ocular, none. 



Illuminant, blow- through lime -light jet. 



Condenser, Swift achromatic. 



No auxiliary condenser. 



Cam era -length , 5 ft. 6 in. 



