166 BACTERIOLOGY 



temperature as well as in the incubator, but not below 12 

 or 14 C., and their highest limit of vitality is at 45 C. If 

 the cells are frozen they again recover, according to Frisch, 

 the capability of further development w r hen the temperature 

 is raised. The formation of spores can be observed with 

 distinctness. 



The cells stain readily with aniline dyes, and do not 

 discharge their colour if Gram's method be employed, a 

 behaviour which is of particular importance for the detec- 

 tion of the bacilli in the blood or organs. A minute portion 

 of the spleen is usually taken, rubbed between two cover- 

 glasses, and submitted to Gram's process of staining ; but 



Chains of anthrax bacilli 



Solitary bacilli 



Spaces between the 

 ^ rods of a chain 



Bacilli containing spores 

 FIG. 63. BACILLI OF ANTHRAX. 



the heating must not be carried too far, otherwise the 

 protoplasm inside the. limiting membrane of the cell will 

 undergo fine granulation. Carbolic fuchsine or carbolic 

 methyl blue are also used for rapid staining. The cells 

 sometimes have their ends thickened into knobs and with 

 shallow excavations, so that an oval light spot appears 

 between the individual cells, or, owing to the thickened 

 nodes, they assume the figure of a bamboo rod. This latter 

 appearance is w r ell brought out by double staining with 

 Bismarck brown and methyl blue. 



When the anthrax bacillus is grown in bouillon, long 

 fibres are obtained which are felted together in the form of 

 a tress of hair, an appearance w r hich becomes visible in 



