§ XII.] 



Anthrax. 



123 



Bacillus Anthracis is distinguished under the microscope by 

 the absence of independent motion and by the form of its ger- 

 mination from B. subtilis, which is very much like it in almost 

 all respects, except that it is usually more slender and is not 

 parasitic. To these must be added in 

 ordinary cases the macroscopic dis- 

 tinction, that B. Anthracis at the 

 highest point of its development forms 

 a floccose sediment in nutrient solu- 

 tions, while B. subtilis forms the dry 

 membrane on the surface mentioned 

 on page 12. Some exceptional phe- 

 nomena will be noticed further on. 



Anthrax chiefly attacks mammals, 

 and among these the most liable to 

 it are herbivorous animals, especially 

 rodents and ruminants ; of the species 

 which have been observed, domestic 

 mice, guinea-pigs, rabbits, sheep, and 

 homed cattle are the most susceptible 

 in the order of naming. The next in 

 the degree of liability are omnivorous 

 animals, and among them men ; then 

 come the carnivores, and among these cats, for instance, are 

 more frequently attacked than dogs. Birds also are said to be 

 susceptible to the disease, though this has been disputed ; Gibier 

 found that frogs, and Metschnikoflf that lizards (Lacerta viridis) 

 were susceptible when they were kept at about the temperature 

 of the bodies of warm-blooded animals. We will pass over 



Fig. 17. Bacillus Anthracis. a portion of a group of vigorously growing 

 filaments ; the segmentation into cells is not visible, but has nevertheless 

 taken place, b three successive stages of a germinating spore ; close by is 

 a ripe spore s before germination, c rod from the blood of an infected 

 guinea-pig some hours after the death of the animal, after treatment with 

 distilled water, a and b from cultures on microscope-slides in solution of 

 extract of meat. Magu. 600-700 times. 



Fig. 1 7. 



