Speculation 



353 

 Man 



susceptible; birds, reptiles and amphibians usually immune, 

 is susceptible in varying degree. 



Anthrax was one of the first infectious diseases proved to depend 

 upon a specific micro-organism. As early as 1849 Pollender* dis- 

 covered small rod-shaped bodies in the blood of animals suffering 

 from anthrax, but the exact relation which they bore to the disease 

 was not pointed out until 1863, when Davaine,fbya series of in- 

 teresting experiments, proved their etiologic significance to most 

 unbiased minds. The final confirmation of Davaine's conclusions 

 and actual proof of the matter rested with Koch,| who, observing 



Fig. 128. Bacillus anthracis; showing the capsules. From a case of human 

 infection. Magnified 1000 diameters (Schwalbe). 



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 is a large rod-shaped organ- 

 ism, of rectangular form, with slightly rounded corners. It meas- 

 ures 5 to 20 JJL in length and from i to 1.25/4 in breadth. It has a 

 pronounced tendency to form long threads, in which, however, the 

 individuals can usually be made out, the lines of junction of the com- 

 ponent bacilli giving the thread somewhat the appearance of a 

 bamboo rod. In preparations made by staining blood or other 

 animal juices the bacilli often appear surrounded by transparent 

 capsules. Such are not found in specimens made from artificial 

 cultures. 



Sporulation. The formation of endospores is prolific in the pres- 



* "Vierteljahrsschr. fur ger., Med.," 1855, Bd. vm. 

 t "Compte-rendu," 1863, Ivii. 

 t "Beitrage zur Biol. d. Pflanzen," 1876, n. 

 23 



