428 THE BACILLUS OF ANTHRAX. 
Pathogenesis.—The anthrax bacillus is pathogenic for cattle, 
sheep, horses, rabbits, guinea-pigs, and mice. White rats, dogs, and 
frogs are immune, as is also the Algerian race of sheep. The spar- 
row is susceptible to general infection, but chickens, under normal 
conditions, are not. Young animals are, as a rule, more susceptible 
than adults of the same species. Man does not belong among the 
most susceptible animals, but is subject to local infection as a result 
of accidental inoculation—malignant pustule—and to pulmonic an- 
thrax from breathing air, containing spores of the anthrax bacillus, 
during the sorting of wool or hair from infected animals. In animals 
which havea partial immunity, natural or acquired, as a result of 
inoculations with attenuated virus, the subcutaneous introduction of 
virulent cultures may give rise to a limited local inflammatory pro- 
cess, with effusion of bloody serum in which the bacillus is found in 
considerable numbers ; but the blood is not invaded, and the animal, 
after some slight symptoms of indisposition, recovers. In susceptible 
Fig. 102.—Bacillus anthracis in liver of mouse. x 700. (Fligge.) 
animals injections beneath the skin or into a vein give rise to general 
infection, and the bacilli multiply rapidly in the circulating fluid. 
Death occurs in mice within twenty-four hours, and in rabbits, as a. 
rule, in less than forty-eight hours. The blood of the heart and 
large vessels may be found, in an autopsy made immediately after 
death, to contain comparatively few bacilli; but in the capillaries of 
the various organs, and especially in the greatly enlarged spleen, in 
the liver, the kidneys, and the lungs, they will be found in great 
numbers, and well-stained sections of these organs will give an as- 
tonishing picture under the microscope, which the student should not 
fail to see in preparations made by himself. The capillaries in many 
places will be found stuffed full of bacilli; or they may even be rup- 
