164 VETERINARY STUDIES 



(2) When infection is introduced by inoculation through 

 the skin, there results the condition known as external anthrax, 

 carbuncular disease, inoculation anthrax, or malignant pustule. 

 This may be occasioned by insects, especially of the blood-suck- 

 ing varieties, such as the various horse or gad flies; probably, 

 also, by some varieties of the mosquito. The infection may 

 come through wounds made by infected instruments or uten- 

 sils; or by wounds coming in contact with virulent material. 

 In the Lower IMississippi Valley the external form occurs very 

 frequently, and some outbreaks extend over considerable terri- 

 tory, among horses and mules, on account of the vast numbers 

 of horseflies during the summer months. 



(3) Infection may occur through the digestive tract. This 

 internal, or intestinal, form of anthrax is generally produced 

 by taking the virus in contaminated food or water. 



Methods of introduction and spread. — Anthrax virus may be 

 introduced by imported hides, hair, wool, etc., from foreign 

 countries infected with anthrax. Fertilizing materials manu- 

 factured from animals affected with the disease may be a source 

 of infection, also running water may become contaminated and 

 spread infection along its course. The refuse water from tan- 

 neries has been known to disseminate infection from anthrax 

 hides. Insects, after feeding upon infected blood and tissues, 

 may carry the virus to healthy animals at a distance. Insects 

 may probably, also, infect food materials in troughs and man- 

 gers, by conveying virulent matter on their bodies and feet. 

 Carrion birds, through the medium of their excrement or soiled 

 feet, may infect pastures on which they alight. Carnivorous 

 and omnivorous animals, as dogs and hogs, running at large, 

 after feeding upon anthrax carcasses, may carry away viru- 

 lent blood on their feet; and if these animals themselves die, 

 they become fresh centers of the disease. 



Foodstuffs, as grass, cereal grains and their by-products, hay, 

 etc., raised upon lands infected with anthrax spores, may carry 

 those spores and spread the disease. Human beings coming in 

 contact with virulent anthrax material, and having their clothes, 

 shoes, hands, etc., soiled thereby, may spread the disease to 

 animals. Neglect to properly dispose of anthrax carcasses is, 

 perhaps, the factor most responsible for the continuance and 

 spread of anthrax. 



Period of incubation.— The time that elapses between infee- 



