ANTHRAX. 



335 



their etiological significance. The further confirmation 

 of Davaine's conclusions and actual proof of the matter 

 rested with Pasteur and Koch, who, observing that the 

 bacilli bore spores, cultivated them successfully outside 

 the body, and then produced the disease by the inocula- 

 tion of pure cultures. 



The anthrax bacilli (Fig. 109) are large rods with a 



FIG. 109.- 



-Bacillus anthracis : colony three days old upon a gelatin plate ; ad- 

 hesive preparation; x 1000 (Frankel and Pfeiffer). 



rectangular form, caused by the very slight rounding of 

 the corners. They measure 5-20 ft in length and are 

 from i fJL to 1.25 fJ. in breadth. The pronounced tendency 

 is toward the formation of long threads, in which, how- 

 ever, the individuals can generally be made out ; at times 

 isolated rods occur. In the threads the bacilli seem en- 

 larged a little at the ends, and give somewhat the appear- 

 ance of a bamboo cane. The formation of spores is pro- 

 lific : each spore has a distinct oval shape, is transparent, 

 and does not alter the contour of the bacillus in which it 

 occurs. Spores are generally formed in the presence of 

 oxygen upon the surfaces of the culture-media. When a 

 spore is placed under favorable conditions for its devel- 

 opment and is carefully watched, it may be observed to 



