288 CLINICAL BACTERIOLOGY. 



are subject to great variations in size. In cultures the bacillus 

 is prone to be considerably longer than in the animal organism. 

 In the blood of human beings it is shorter than in that of ro- 

 dents; in cattle it is shorter than in white mice and in guinea- 

 pigs. The broad side of the bacillus is slightly rounded. The 

 surfaces of two adjacent bacilli in direct contact are, however, 

 plane. In the blood of animals suffering from anthrax the 

 bacilli are at times collected into small filaments of two or 

 four, or at most five, members. Only attenuated bacilli, just 

 capable of causing death in experimental animals, form long 

 filaments in the organs of the animals. Such filaments are 

 usual in the body of the frog. In cultures, on the other hand, 



Fig. 63. Bacillus anthracis, stained to show the spores ; X 1000 

 (Frankel and Pfeiffer). 



the anthrax-bacillus exhibits an especial tendency to the forma- 

 tion of long, intertwining chains. Frequently, bacilli obtained 

 from the lesions of the disease present a bright border that 

 some observers have looked upon as a capsule. This supposed 

 capsule may be demonstrated by the staining method of Johne 

 in the following manner : The preparation made from the blood 

 or visceral fluid and dried in the air is passed three times 

 through the flame ; stained for from fifteen to thirty seconds 

 in a slightly warmed, two per cent, aqueous solution of 

 gentian-violet ; washed in water ; exposed for ten minutes to 

 the action of a one per cent, solution of acetic acid ; and ex- 

 amined in water. It is important to make the examination in 

 water, as the mucoid capsule is not visible when the specimen is 



