BACILLUS ANTHRACIS AND ANTHRAX 779 



If anthrax bacilli are cultivated for prolonged periods upon 

 media containing hydrochloric or rosolic acid or weak solutions of 

 carbolic acid, 8 cultures may be obtained which do not sporulate 

 and which seem permanently to have lost this power, without 

 losing their virulence to the same degree. Similar results may be 

 obtained by continuous cultivation at temperatures above 42 C. 

 By this procedure, however, virulence, too, is considerably di- 

 minished. 



Resistance. Because of its property of spore formation, the 

 anthrax bacillus is extremely resistant toward chemical and physical 

 environment. The vegetative forms themselves are not more resist- 

 ant than most other non-sporulating bacteria, being destroyed by 

 a temperature of 54 C. in ten minutes. Anthrax spores may be 

 kept in a dry state for many years without losing their viability. 9 

 While different strains of anthrax spores show some variation in 

 their powers of resistance, all races show an extremely high resist- 

 ance to heat. Dry heat at 140 C. kills them only after three 

 hours. 10 Live steam at 100 kills them in five to ten minutes. Boil- 

 ing in water destroys them in about ten minutes. Low temperatures 

 have but little effect upon them. Ravenel 11 found that, frozen by 

 liquid air, they were still viable after three hours. 



The variability shown by different strains of spores in their 

 resistance to heat is even more marked in their behavior toward 

 chemicals. 12 Some strains will retain their viability after exposure 

 to 5 per cent carbolic acid for forty days, 13 while others are destroyed 

 by the same solution in two days. Corrosive sublimate, 1 :2,000, 

 kills most strains of anthrax in forty minutes. 



Direct sunlight destroys anthrax spores within six to twelve 

 hours. 14 



Pathogenicity. The anthrax bacillus is pathogenic for cattle, 

 sheep, guinea-pigs, rabbits, rats, and mice. The degrees of sus- 

 ceptibility of these animals differ greatly, variations in this respect 

 existing even among different members of the same species. Thus, 



8 Chamberland et Roux, Comptes rend, de 1'acad. des sci., xcvi, 1882. 



9 Surmnnt et Arnould, Ann. de 1'inst. Pasteur, 1894. 



10 Koc.h und Wolff hiigel, Mitt. a. d. kais. Gesundheitsamt, 1881. 



11 Raw'n-rl, Medical News, vii, 1899. 



12 FranM, Zeit. f. Hyg., vi, 1889. 



13 Koch, loc. oit. 



14 Momont, Ann. de Finst. Pasteur, 1892. 



