212 MICRO-ORGANISMS AND DISEASE. [CHAP. 



cultures of the bacillus anthracis, e.g. in broth in which the 

 growth is limited to the bottom of the fluid, the convolutions 

 and the twisted condition of the threads are more pronounced, 

 more cable-like. 



Hay bacillus being motile, every culture of it is uniformly 

 turbid, the bacilli being capable of moving about, and after a 

 day or two of incubation at 35" C. they form a distinct pellicle 

 on the surface of the fluid, which in further stages becomes 

 complete and thick. These pellicles are composed of a 

 dense feltwork of threads of the bacilli, and in them spore- 

 formation is going on. 



By shaking the fluid the pellicle sinks to the bottom, and if 

 the fluid is not exhausted yet, a new pellicle is formed of the 

 same nature. 



In no culture of hay bacillus are there ever observed those 

 cloudy, fluffy, whitish and transparent convolutions that are 

 seen in cultivations of bacillus anthracis carried on at the 

 bottom of fluid broth, and which have been so accurately 

 described by Pasteur. 



Both the hay bacillus and the anthrax bacillus when 

 growing on gelatine mixtures liquefy the gelatine ; both 

 when growing in meat broth turn the at first colourless fluid 

 in the course of incubation to an amber, and further to a 

 brown, tint. 



The hay bacillus is capable of thriving well in acid 

 solutions, it grows copiously in hay infusion, which is of a 

 distinct acid reaction ; the bacillus anthracis, although capable 

 of making a slight progress in acid hay infusion, does 

 not get far, for degeneration soon sets in ; it thrives best in 

 neutral solutions. Hay bacillus thrives also very well in 

 neutral solutions. 



Buchner states, that by successive cultivation of bacillus 

 anthracis under constant variation of the nutritive material, 



