474 



Anthrax 



proved their etiologic significance to most unbiased minds. 

 The final 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 produced the disease by 

 the inoculation of pure cultures. 



Morphology. The anthrax bacillus (Fig. 141) is a large 

 rod-shaped organism, of rectangular form, with slightly 

 rounded corners. It measures 5-20/2 in length and from 

 i fj. to i.25// in breadth. It has a pronounced tendency 



Fig. 141. Bacillus anthracis; colony three days old upon a gelatin 

 plate; adhesive preparation. x'lOOO (Frankel and Pfeiffer). 



to form long threads, in which, however, the individuals 

 can usually be made out, the lines of junction of the 

 component bacilli giving the thread somewhat the appear- 

 ance of a bamboo rod. 



Speculation. The formation of endospores is prolific: 

 each spore has a distinct oval shape, is transparent, situated 

 at the center of the bacillus in which it occurs. It does not 

 alter the contour of the bacillus. The spores are formed 

 only in the presence of oxygen upon the surfaces of the 

 culture media. When a spore is placed under conditions 

 favorable to its development, it increases in length and 

 ruptures at the end, from which the new bacillus escapes. 



