Natural Infection. 7 



spores. When taken into the digestive tract with the food or 

 water some survive the action of the gastric juice and pass 

 through the stomach unimpaired, germinating in the alkaline 

 contents of the intestines where they multiply b}^ fission. The 

 bacilli enter the lymph spaces of the intestines and finally reach 

 the blood through the lymph stream. 



The contamination of the food with bacilli and spores 

 usually takes place from the infected soil on which it was grown. 

 Anthrax bacilli which in some way, especially by means of 

 blood or intestinal contents of affected animals, are deposited 

 in the superficial layers of the soil may there remain alive for 

 some time, and under favorable moisture and temperatures 

 multiply or form spores. The spores are for a long time capa- 

 ble of propagation, resisting dryness and moisture, cold and 

 heat, as well as putrefaction, until favoral)le germinating con- 

 ditions arise, whereupon the bacilli continue to multiply and 

 produce new spores. Under unfavorable conditions, such as 

 excessive dryness or cold, the bacilli are destroyed, but the 

 spores resist such influences. In this manner the soil of a 

 certain locality which has once become infected may remain a 

 source of infection for a very long time. 



The elevation as well as the moisture and temperature of 

 the soil are naturally of great importance. The infective agent 

 thrives best in moist soil rich in organic matter, generally in 

 swampy, marshy soil, or in localities subject to periodical inun- 

 dations. In such places anthrax usually appears when by a 

 rapid recession of the ground-water the superficial layers of 

 the soil become exposed, and then, in the presence of proper 

 moisture and temperature, germination of the spores and mul- 

 tiplication of the bacilli results. Consequently the disease is 

 observed most frequently during the summer time, particularly 

 in warm days following a period of rainy weather. 



Forage plants are very apt to transmit the disease since 

 the animals always ingest with their food a certain quantity of 

 dirt which adheres to the dried and stored feed. Further, in 

 the infected localities the water contained in pools as well as 

 that from springs may become contaminated. As a matter of 

 fact various outbreaks in pastures may be due to the use of 

 certain springs, particularly if they are shallow. 



The infectious material contaminates the soil in many ways. 

 The running surface water may carry along the spores and 

 deposit them elsewhere. Likewise, the wind may carry them 

 to previously uninfected localities from places where the water 

 has receded and the surface layer of the soil has become dried. 

 Most frequently, however, the soil becomes infected by carcasses 

 or parts of carcasses as well as by the excrements of affected 

 animals. While the bacilli do not produce spores in the carcass, 

 yet they pass to the outside, either through the body orifices 

 or through decomposition of the carcass, when they form 



