CHAPTER XXVII. 



Study of Bacterium Anthracis, and of the Effects Produced by Its Inocu- 

 lation into Animals Peculiarities of the Organism Under Varying Con- 

 ditions of Surroundings Anthrax Vaccines Anthrax Immune Serum. 



THE discovery that the blood of animals suffering from 

 splenic fever, or anthrax, always contains minute rod-shaped 

 bodies (Pollender, 1855; Davaine, 1863), led to a group of 

 investigations that have not only fully familiarized us with 

 the nature of this malady in particular, but have perhaps 

 contributed more, incidentally, to our knowledge of bac- 

 teriology in general than studies upon any other single 

 infective process or its causative agent. 



The direct outcome of these investigations is that a rod- 

 shaped micro-organism, now known as bacterium anthracis, 

 is always present in the blood of animals suffering from this 

 disease; that this organism can be obtained from the tissue 

 of those animals in pure cultures; and that such artificial 

 cultures of bacterium anthracis when introduced into the 

 bodies of susceptible animals can again produce a condition 

 identical with that found in the animal from which they 

 were obtained. The disease is a true septicemia, and after 

 death the capillaries throughout the body are always found 

 to contain the typical rod-shaped organism in larger or 

 smaller numbers. 



This organism, when isolated in pure culture, is a bac- 

 terium which varies considerably in length, ranging from 

 short rods, 2 to 3/z in length, to longer threads, 20 to 25/z 

 556) 



