CHANNELS OF INFECTION 



85 



Fig. 12. Anthrax bacteria in a cover-glass preparation of blood 

 showing chains and capsules. 



bone fertilizers, hides, hair or wool from infected countries. 

 When the extent of this traffic is realized, it is easy to under- 

 stand how anthrax has been brought to this countrj^ and why 

 it occasionally appears heie and there over a large part of the 

 continent. Many outbreaks, as well as isolated cases, illus- 

 trating this common method of dissemination are on record. 



J^ 75. Animals attacked. Nearly all animals suffer 

 from anthrax. The herbivora and rodents are most suscepti- 

 ble. It is interesting to note that the Algerian race of sheep 

 are immune. A satisfactory explanation for this striking 

 exception has not been recorded. It has been stated that a 

 single bacterium introduced into the subcutaneous connective 

 tissue of a guinea-pig or mouse is sufficient to kill. Cats, 

 tame and wild rabbits, and hares are the next most susceptible 

 species. It is stated that dogs, pigs, and foxes are very 

 slightly susceptible. Rats, fowls and pigeons are reported to 

 be immune. Fish and amphibia are rarely attacked. 



§ 76. Channels of infection. Three common modes of 

 infection are recognized for anthrax, namely : through the 

 digestive tract, by the skin and by the lungs. In cattle the 

 infection seems to be largely through the alimentary canal ; 

 in horses and sheep by the skin or digestive tract ; in men 



