THE BACILLUS OF ANTHRAX. 423 



anthrax in susceptible animals as certainly as does the blood of an 

 animal recently dead from the disease. 



Owing to the fact that this was the first pathogenic bacillus cul- 

 tivated in artificial media, and to the facility with which it grows in 

 various media, it has served more than any other microorganism for 

 researches relating to a variety of questions in pathology, general 

 biology, and public hygiene, some of which are discussed in other 

 sections of this volume. 



BACILLUS ANTHRACIS. 



Synonyms. Milzbrandbacillus, Ger.; Bacteridie du charbon, Fr. 



First observed in the blood of infected animals by Pollender (1849) 



and by Davaine (1850). Etiological relation affirmed by Davaine 



FIG. 98. Bacillus anthracis, from a culture, showing development of long threads in convo- 

 luted bundles, x 300. (Klein.) 



(1863), and established by the inoculation of pure cultures by Pasteur 

 (1879) and by many other investigators. 



Morphology. Rod-shaped bacteria having a breadth of 1 to 

 1.25 /*, and 5 to 20 ^ in length; or, in suitable culture media, growing- 

 out into long, flexible filaments, which are frequently united in 

 twisted, cord-like bundles. These filaments in hanging-drop cul- 

 tures, before the development of spores, appear to be homogeneous ; 

 or the protoplasm is clouded and granular, but without distinct seg- 

 mentation. But in stained preparations the filaments are seen to be 

 made up of a series of rectangular, deeply stained segments. In 

 hanging-drop cultures the ends of the rods appear rounded, but in 

 stained preparations from the blood of an infected animal they are 

 seen to present a slight concavity, and a lenticular interspace is 

 formed where two rods come together. The diameter of the rods 



