ANTHRAX 81 



are not seen in all preparations. Many bacilli show capsules which 

 are less deeply stained and the contrast is quite striking. It is sup- 

 posed that this capsule protects the bacillus against the destructive 

 action of the secretions of the body cells. At least, bacilli taken from 

 infected animals generally show the capsules, while subcultures seldom 

 do. It has been found that cultures grown in fluid blood serum do 

 show the capsule. These facts indicate that the capsule results from 

 some reaction between the organism and blood. It will continue to 

 live, but will not multiply in the absence of air and consequently must 

 be classed as an aerobe. It grows under a wide range of temperature 

 (15 to 43 C), but its optimum growth is at or near the temperature 

 of the animal body (37 to 38 C.). 



It grows easily on all the ordinary culture media. In undis- 

 turbed bouillon it does not produce a uniform cloudiness, but appears 

 in floccules. On gelatine plates after from two to three days at from 

 18 to 20 C. it develops characteristic colonies. Under a low power 

 these are seen to be not compact as is the case with most bacterial 

 colonies, but loosely aggregated. The edges are not smooth and 

 sharply defined, but more or less fringed. These are known as medusa 

 forms and the fringe is due, as is shown under a higher power, to 

 the growth of the rods from the central mass into the surrounding 

 medium. It forms a proteolytic ferment which gradually digests or 

 liquefies the gelatine and the colonies subside into the craters thus 

 formed. In stick gelatine cultures the bacillus grows along the line 

 and branches off on the sides forming a picture which has been vari- 

 ously designated as a brush or as an inverted pine tree; very slowly 

 liquefaction proceeds from the surface downward. On agar plates the 

 colonies are much like those on gelatine, with the exception that on 

 the former spore formation may be observed. Stick cultures on agar 

 are much like those on gelatine, with no liquefaction and a spreading 

 of the growth over the surface of the medium. It coagulates milk 

 and then digests the coagulum. With an abundant supply of oxygen 

 digestion may proceed so quickly that coagula are not seen. 



The anthrax bacillus multiplies by transverse fission, but when 

 it finds the conditions of life unfavorable, it does not have to strive 

 against untoward circumstances; it simply develops seeds or spores 

 and passes into a resting stage. In this state it does not need air or 



