164 PUBLIC HEALTH BACTERIOLOGY 



that it is easily demonstrable. It is known as the 

 " capsule " and varies in thickness from being only just 

 visible to 4 or 5 times the size of the bacterium itself. It 

 is mostly seen in preparations taken directly from animal 

 tissues or fluids or exudates, or from cultures in media 

 containing animal serum or milk. It is best seen in the 

 Diplococcus pneumoniae, Micrococcus tetragenus, B. 

 aerogenes capsulatus, and the bacilli of the Friedlaender 

 group. Hiss's method : Make a cover-slip film, and 

 preferably by using a drop of animal serum instead of 

 water. Dry in air and fix by heat. Stain for a few 

 seconds with dilute fuchsin or gentian-violet (1 of saturated 

 alcoholic solution in 19 of aq. dest.), meanwhile heating 

 the preparation over a flame until steam arises. Wash 

 off dye with 20 per cent watery solution of copper 

 sulphate. Blot dry (do not wash with water), and mount 

 direct in Canada balsam. The capsule appears as a faint 

 blue halo around a dark purple cell-body. 



Spore Staining. Prepare film as usual and fix in the 

 flame. Place in CHC1 3 for two minutes. Wash in water. 

 Place in 5 per cent chromic acid for half a minute to two 

 minutes. Wash in water. Float cover-slip, film side down, 

 on carbol-fuchsin solution in a small porcelain basin and 

 heat stain gently until it steams ; continue in stain for 3 to 

 5 minutes. Decolorize in 5 per cent sulphuric acid for 5 to 

 10 seconds. Wash in water. Stain with saturated watery 

 methylene-blue for 30 to 60 seconds. Wash and examine ; 

 or dry, and mount in balsam. The spores are stained red 

 and the cell bodies blue. 



Spores are believed to be an encysted or resting stage 

 of bacteria, and not a method of reproduction, or rather 

 multiplication. In most cases only one spore is produced 

 by one bacillus, and the latter becomes extinct when the 

 spore is fully developed. Spore formation is not very 

 common among bacteria, and is found almost exclusively 

 among the bacilli, less commonly in the spirilla, and rarely, 

 if at all, in micrococci. The anaerobic bacilli are almost 

 all spore-forming, but amongst aerobes the only sporing 

 bacterium pathogenic to man is the anthrax bacillus. 

 This materially facilitates and simplifies the disinfection 

 and treatment of infectious diseases, as spores are extremely 



