58 



CLINICAL BACTERIOLOGY AND HEMATOLOGY 



characteristic appearance if the anthrax bacilli are present in 

 pure culture. The growth takes place in lines which project 

 nearly at right angles to the line of inoculation, and grow more 

 vigorously the nearer they are to the surface. The result is the 

 development of a culture which has a strong resemblance to an 

 inverted fir-tree (Fig. 20). In another day or two the gelatin will 

 begin to show a certain amount of liquefaction, which begins at 

 the surface. 



The appearances in the plate culture are 

 perhaps not quite so characteristic, but they 

 are manifested in impure cultures. The 

 young colonies of anthrax bacilli have a 

 whorled appearance, which has been com- 



FiG. 21. — YonNG Colony of Anthrax Bacillus 

 (x 15). (Crookshank.) 



Fig. 20.— Stab Cul- pared to a barrister's wig or to the head of 

 TnRE OF Anthrax '^ % mi 1 



Bacillus. (Crook- Medusa (Fig. 2 i). The plate should be placed 



^"*'^'^-) upon the stage of the microscope, and 



examined for these colonies with the low 

 power. If one is found, a clean cover-glass should be pressed 

 upon it, lifted up with a needle, so as to bring up the colony with 

 it, fixed by heat, and stained with carbol thionin or methylene 

 blue. The colonies are most characteristic after two days' 

 incubation ; at a later period the gelatin is liquefied and spores 

 are formed. 



A culture which presents these cultural and morphological 

 appearances may be considered to be one of anthrax with almost 

 absolute certainty, though other tests (notably animal tests) would 

 be applied in a laboratory. 



