Anthrax. 237 



Certain conditions, however, contribute to the propagation and 

 reception of the bacillus and these may be considered as accessory 

 causes. 



Animals susceptible. The receptivity of the animal exposed 

 is of first importance. Young animals are the most susceptible. 

 The small rodents, the mouse, Guinea pig and rabbit are suscep- 

 tible in the order named, followed by the sheep and horse and 

 these again by the camel and ox. Among the wild herbivora the 

 goat, deer, and stag have a high susceptibility. Man is less sus- 

 ceptible yet contracts the disease readily by inoculation, inhala- 

 tion or ingestion. Swine and dogs are comparatively little suscep- 

 ible, yet they often contract the disease by eating the carcasses 

 or discharges of anthrax animals. White rats and birds are held 

 to be insusceptible, yet the latter contract the disease readily 

 when the vitality of the system has been reduced by immersing 

 the body in water, or giving antipyrine. A similar result is 

 observed in the otherwise immune frog if the body is heated 

 above the normal cold blooded temperature. The receptivity 

 may vary, however, in the same genus and species. The Alger- 

 ian sheep is virtually immune from anthrax, perhaps because its 

 ancestors have been so constantly exposed that only the insuscep- 

 tible strains survived. Swine, birds and carnivora may have 

 similarly acquired a fair measure of immunity by the survival of 

 the fittest. Apart from this, however, a flesh diet is to a certain 

 extent protective, thus Feser's rats if fed vegetable food proved 

 susceptible to inoculated anthrax, while if fed on animal food they 

 were comparatively immune. 



The animal that has survived an attack of anthrax is thereafter 

 strongly immune. This serves to partly explain the apparent 

 immunity of animals bred in an anthrax district, the young animal 

 becoming habituated to infinitesimal doses of the toxins, conveyed 

 in the secretions of the uterine glands or mammse. 



SoilSs a factor so far as it preserves and propagates the bacillus. 

 As already stated, soils that are naturally wet by reason of their 

 impermeable character, their position on or near the water level, 

 their conformation in basins which dry out in late summer or 

 autumn, are especially favorable to preservation of the bacillus. 

 Again soils that are especially rich by reason of an excess of 

 decomposing vegetable and animal remains, or because of exces- 

 sive manuring, tend to preserve and multiply the microbe. Rich, 



