292 PEACTICAL PHOTO-MICBOGKAPHY 



Condenser, Swift achromatic, with top combination re- 

 moved, and central stop to obtain dark-ground illumination. 



Parallel beam projected into condenser by means of ordinary 

 bull's-eye. 



Screen, green pot-glass. 



Plate, Edward's isochromatic, medium rapidity. 



Exposure, 30 seconds. 



Development, pyro-soda. 



PLATE V, FIG. 1. Tripanosoma gambiense. x 450. 



Stained by Piomanowsky-Leishman method. (Methylene- 

 blue-eosin.) 



One-quarter-inch objective, by James Swift & Son. 



Projection-ocular, 4. 



Camera-extension, 2 ft. 9 in. 



Illuminant, one-ampere Nernst lamp. 

 Zeiss auxiliary collecting-lenses Nos. I and III, projecting 

 an enlarged image of the illuminant on to the sub-stage iris- 

 diaphragm. 



Leitz oil-immersion condenser with top removed, working 

 therefore as a dry condenser of relatively low aperture, but 

 sufficient N.A. to completely fill the back lens of the objective. 



Green screen composed of two separate solutions of acid- 

 green and tartrazine in cells 5 mm. thick. The specimen 

 being double stained red and blue, this ensures the utmost 

 contrast. 



Exposure, 30 seconds. 



Plate, Edward's isochromatic, medium speed. 



Development by pyro-soda, but rather weak in pyro to bring 

 out the utmost detail in the body part of the organisms. These, 

 and similar organisms, should be treated much in the same way 

 as in photographing bacteria. The largest possible illumi- 

 nating-cone should be used to ensure that the flagellae are 

 brought out as fine and sharp as possible. 



PLATE V, FIG. 2. Diatom : Orihonies splendida. x 500. 



Objective, ^-inch, dry, No. 6 (N.A., 0-85) ; tube-length, 

 160 mm. by C. Keichert, Vienna. (This objective was one 

 of a series, placed at the disposal of the writer by the 

 courtesy of Messrs. H. F. Angus & Co. of Wigmore Street. 

 London.) 



