ANTHRAX SPORES 309 



geneous appearance of the protoplasm changes and be- 

 comes granular. Ultra-violet rays are stated by Mme. 

 Henri to produce marked mutations of the anthrax bacillus 

 (see p. 6). Spores are formed in all culture media when 

 there has been free access of oxygen, as in surface cultures 

 on potato and agar, but in a deep broth culture, where 

 the supply is limited, spore-formation is absent or very 

 scanty. Spores are never met with in the living animal ; 

 they only appear some hours after death, or when matter 

 containing the bacilli comes in contact with air, as in the 

 bloody discharges from the body. It has therefore been 

 supposed that oxygen is necessary for spore-formation 

 to take place, but this does not seem to be the whole 

 explanation, for spores form in an atmosphere of nitrogen, 

 though they do not do so in one of hydrogen. The life 

 history of the organism and the development of spores 

 can be watched in a hanging-drop specimen prepared by 

 inoculating a droplet of broth with the blood of an infected 

 animal. The preparation may be observed on a warm 

 stage, or be examined at stated times, being kept in the 

 intervals in the blood-heat incubator. At the end of 

 twenty-four hours the short filaments, which alone are 

 present in the blood, will have grown so long that they 

 stretch across the field, while the protoplasm has become 

 granular and minute shining points are visible here and 

 there. In another twenty-four hours the filaments 

 extend, the protoplasm becomes still more granular, and 

 the shining spots are now well-marked ovoid, highly 

 refractile bodies the mature spores. In old cultures 

 the rods and filaments almost disappear, numbers of 

 spores alone remaining. These spores, when placed 

 under favourable conditions of moisture, warmth, and 

 nutriment, again produce rods and filaments ; at the 

 extremity of the long diameter a little bud appears, 

 grows in length and ultimately becomes a mature rod, 



