PLATE 34. 



Bacteria. 



A BACTERIA FROM AN INFUSION OF PEAS x 1250 



The preparation contains several forms of bacteria derived from 

 air-borne spores which have settled in an infusion of peas and 

 developed in a few days. The most noticeable is a comparatively large 

 organism containing granules which have taken up and hold the 

 stain more tenaciously than the rest of the protoplasm. 



Stained in gentian violet. 



B Bacillus tuberculosis x 1250 



A cover-glass preparation of Sputum made to determine the 

 existence of tuberculosis. 



The bacilli stained red with carbol fuchsine, the nuclei of the 

 pus cells countcrstaincd in methylene blue. 



Objective Leitz -^" oil immersion Achromat. N.A. 1.30. 



Ocular Zeiss Projection x 4. 



Condenser ... Watson's Holos. immersion, N.A. 1.30, oiled to 



slip, full aperture. 



Illuminant ... Liliput 4 amp. arc. 

 Aux. Condenser Double convex lens, giving parallel beam. 



Screen Wrattcn's B (green) and E (orange). 



Plate Imperial N.F. 



Exposure ... ... 5 sec. and 10 sec. 



Developer ... Pyro-soda. 



The manipulative details for the photomicrography of bacteria are 

 given on page 240. The use of a wide cone of light, and of yellow- 

 green monochromatic light \= 5600-6100 to increase contrast and 

 improve definition should be noted. 



The methods of preparation arc given on page 242. 



Bacteria as test objects. The sharpness of the images of bacteria 

 taken under these conditions is a good criterion of the qualities of an 

 objective. The beaded structure of B. tuberculosis is characteristic. 



Photos. W. B. R. , (To follow Plate 33 and page 240. 



