Natural Infection. 9 



or less fat in the prepared product (Lelmert). Lastly, tlie soil, 

 as well as the food and drinking water may occasionally become 

 infected by drainage water and waste from tanneries, wool- 

 works and horse-hair mills (Grebe, Ulilich; Gartner & Dam- 

 mann found that while keeping the skins in the lime pit during 

 the process of tanning the anthrax spores are not destroyed). 



The introduction of a large quantity of spores is necessary for an 

 active infection, and accordingly anthrax infections usually appear 

 only after the ingestion of a considerable quantity of infected food or 

 drinking water. The necessary quantity of spores varies with the indi- 

 vidual susceptibility or resistance which may be influenced by internal 

 and external conditions. Animals which are affected with the so-called 

 "latent infection" (or the above mentioned "spore carriers") not 

 infrequently develop the disease as a result of external weakening influ- 

 ences through colds, physical exertion, starvation, etc. Furthermore, 

 by repeated though slight intercurrent attacks the resistance of the 

 animals is reduced, and under such conditions the anthrax bacilli 

 begin to multiply, and thus produce the specific affection. (According 

 to Oppermann healthy sheep may be infected by the feeding of 200,000 

 spores, while sheep which were previously starved were infected by 

 feeding 51,000 spores). A reduction in the natural resistance is also 

 claimed to be caused by protective inoculation, according to Leclainche 

 & Vallee, and some of the losses from inoculation may be explainable 

 in this way. 



Carnivorous animals usually become infected after ingest- 

 ing meat or blood of anthrax animals. If the meat is fresh it 

 contains only bacilli which are usually destroyed in the stomach. 

 On the other hand, if the meat has stood for a sufficient length 

 of time for the spores to develop on its surface and a large 

 amount is ingested at one time the spores may pass through 

 the stomach and germinate in the intestinal tract. In some 

 instances, indeed, it may be assumed that even fresh anthrax 

 meat may cause infection, provided the animals have eaten at 

 one time such a large quantity as to cause a portion of it to 

 leave the stomach undigested. In all cases there exists the 

 possibility of the infection occurring through the mucous mem- 

 brane of the mouth and pharynx, particularly in the presence 

 of bone splinters ; from the clinical appearance of the affection 

 in hogs which is usually manifested as a pharyngitis and ulcer- 

 ative stomatitis, it seems evident that the entrance of anthrax 

 bacteria into the tissues occurs through the pharynx. 



The milk of affected animals does not transmit the infec- 

 tion as the bacilli do not pass into the milk from the blood 

 unless during the last hours of life. Moreover, the milk secre- 

 tion ceases almost completely very early in the disease. 



Anthrax very rarely develops through skin abrasions, and 

 only in those instances in which the injury to the skin extends 

 through the epithelial layer. In this way bacilli as well as 

 spores may enter the tissue fluids, and in such cases the in- 

 fection is transmitted through the blood, the excretions and 



