22 A MANUAL OF BACTERIOLOGY 



The blue colour is a great help to the eyes, and 

 also throws up the stained specimen with more dis- 

 tinctness.' 



Microplwtograpliic Apparatus. The application of 

 photography as a means of illustrating microscopic 

 preparations has been, on the whole, successful. 

 Koch, Crookshank, Van Ermengern, and others, have 

 produced beautiful photographs of microbes and 

 sections of diseased tissues. For this purpose many 

 different kinds of apparatus have been devised ; but 

 one of the best is represented in Fig. 4. It consists 

 of two tables (A and S) for the microscope and 

 camera respectively ; two diaphragm carriers (E and 

 F) for use with sunlight ; an electric lamp (C) ; a 

 holder for taking absorption cells (H); a water 

 chamber for absorbing heat rays (T); a camera (K); 

 a collective lens-system for projecting the image of 

 the carbon points on the focussing screen (L) this 

 is required when the electric lamp is used ; a micro- 

 scope (M) ; and focussing apparatus (a, b, b', h). 

 This apparatus can be used with sunlight, 1 lime- 

 light, electric-light, and lamp-light. For micro- 

 photographic purposes, microscopic preparations are 

 best when stained yellow, black, or brown, and 

 mounted in either Canada balsam (dissolved in 

 xylol) or a saturated solution of potassium acetate. 

 Several authors have recommended the use of the 

 isochromatic dry-plates, and first-class photographs 

 have been obtained by them. 2 



1 When sunlight is used, a heliostat is also necessary. 



2 See Crookshank's Photography of Bacteria; and Van Enn- 

 engem in Bulletin de la Soc. Beige de Microscopie, No. 10, 1884. 



