402 Anthrax 



Morphology. The anthrax bacillus is a large 'rod-shaped 

 organism, of rectangular form, with slightly rounded cor- 

 ners. It measures 5 to 20 ^ in length and from i to 

 1.25 ^ in breadth. It has a pronounced tendency to 

 form long threads, in which, however, the individuals can 

 usually be made out, the lines of junction of the com- 

 ponent bacilli giving the thread somewhat the appear- 

 ance of a bamboo rod. In preparations made by staining 

 blood or other animal juices the bacilli often appear sur- 

 rounded by transparent capsules. Such are not found in 

 specimens made from artificial cultures. 



' 



'. 



.. 



-y* ; # 



,,; <T, 

 I ' 



\ * 



Fig. 124. Bacillus anthracis, stained to show the spores. X 1000 

 (Frankel and Pfeiffer). 



Sporulation. The formation of endospores is prolific: 

 each spore has a distinct oval shape, is transparent, situated 

 at the center of the bacillus in which it occurs. It does not 

 alter the contour of the bacillus. The spores are formed 

 only in the presence of oxygen upon the surfaces of the 

 culture-media. When a spore is placed under conditions 

 favorable to its development, it increases in length and 

 ruptures at the end, from which the new bacillus escapes. 

 The spores of the anthrax bacillus, being large and readily 

 obtainable, form excellent subjects for the study of spore- 

 formation and germination, for the study of the action of 

 germicides and antiseptics, and for staining. 



