242 PHOTOMICROGRAPHY 



gelatine in the colour with which the bacteria are stained, 

 is generally all that is required. 



Preparation of Bacteria for Photomicrography. The 

 photomicrographs of Bacillus typhosus and Bacillus 

 anthracis were from preparations by Baker ; the typhoid 

 bacillus is stained by a process of deposition in order 

 to render the flagellae distinct, and in consequence a 

 deposit of black spots over the field is unavoidable. 

 Very simple methods, of which the following is an outline, 

 were employed for the other preparations. A small drop 

 of the growth in liquid culture medium, or a small portion 

 of sputum, etc., is placed on a cover-glass, covered with 

 another, and the two glasses pressed together withfinger and 

 thumb to obtain as thin and even a film as possible. The 

 cover-glasses are then slid apart and set aside to dry, and 

 afterwards passed rapidly through a Bunsen flame three 

 times to fix the bacteria. The staining process which 

 follows differs for the different organisms. Formulae for 

 the stains are given on page 266. 



Spirochceta plicatilis from water containing decaying algce. 

 Spirillum from an infusion of Peas (Plates 33 and 34). 

 These were stained by the simplest process, immersion 

 of the cover-glass in a dilute solution of the dye, Gentian 

 violet, for a few minutes, followed by a wash in water, 

 and afterwards in \ % acetic acid if too deeply stained ; 

 finally washed in water and put aside until quite dry, 

 or dehydrated in absolute alcohol and cleared in xylene. 

 A drop of Canada balsam was placed on the centre of the 

 preparation, the cover-glass turned over on to a slip, 

 gently pressed, and the slide allowed to dry. 



Swab from the Throat of a Diphtheria Patient. Plate 33. c 

 showing the Klebs-Loffler bacillus. The preparation was 

 immersed in Loftier 's methylene blue solution for 3 

 minutes, washed in water and finished off as above. 



Bacillus Tuberculosis from Sputum (Plate 34. B). * 

 Carbol-fuchsine warmed in a test-tube was poured on 



