248 ANTHRAX BACILLUS 



and staphylococcus are also antagonistic to anthrax, but to a less 

 degree. 



Modes of Infection under Natural Conditions. Robert Koch has done 

 more than anyone else to show how anthrax is spread by the secretions 

 of sick animals and from cadavers. The excreta and the hemorrhagic 

 discharges from the mouth, nose, and anus contain anthrax bacilli, 

 which are likely to invade barns and pastures. Bacilli are also spread 

 when cadavers are skinned and opened and when they are buried super- 

 ficially. Spore formation occurs under all these conditions. While 

 anthrax bacilli themselves easily perish in the presence of numerous 

 putrefactive bacteria, spores when once formed are very resistant 

 and can survive in moist and dry soil for two or three years, in water 

 for seventeen months, and in cesspools for fifteen months. After 

 spores have formed they may be spread by infected hides and by hay 

 collected from infected pastures and stored in barns. Ravenel was able 

 to show that anthrax was spread by a tannery working with infected 

 hides; others have demonstrated the persistence of anthrax spores for 

 twelve to twenty years in sand in which an anthrax cadaver had been 

 superficially buried. Kitasato, on the other hand, demonstrated that 

 there is no spore formation in an infected cadaver buried as deep as 

 six feet. By far the most common route of infection is by the ingestion 

 of food contaminated with anthrax spores. The vegetative form, i. e., 

 the bacillus, when taken into the healthy stomach, is probably always, 

 at least generally, destroyed by the gastric juice; but the spores pass 

 the stomach and germinate in the intestines, where the bacilli multiply 

 and break through the mucous membrane into the general circulation. 

 Domestic animals also show an inoculation anthrax through wounds 

 of the buccal mucosa or skin. Pulmonary inhalation anthrax prob- 

 ably does not occur among domestic animals. Intestinal anthrax is 

 not always contracted in the pasture, and may, during winter, be 

 contracted from stored infected hay. 



It has been observed that anthrax sometimes occurs sporadically 

 in a single animal or a few individuals of a herd while the great 

 majority escape entirely. Sobernheim believes this to be due to a 

 mild unnoticed form of anthrax common among cattle and sheep in 

 anthrax-infected neighborhoods, which leads to immunization of the 

 majority of the herd by a natural mild infection. 



Anthrax in man occurs chiefly in persons who are exposed to the 

 disease by means of infected hides, wool, and other similar carriers. 

 The most common form is the local wound infection, the anthrax 

 carbuncle; the inhalation pulmonary form follows, and the ingestion 

 intestinal form is least common. The cutaneous form usually ends in 

 recovery, while the pulmonary and intestinal forms, as a rule, lead 

 rapidly to a fatal termination. 



Diagnosis. While the clinical symptoms and anatomical findings 

 in anthrax are quite characteristic, they more or less resemble those 

 of emphysematous anthrax or black-leg, malignant edema, hemor- 



