226 MICROBIOLOGY 



tipper part of the tube appears as a tough, stringy, fluffy mass. 

 A general clouding of the liquid is produced only by vigorous 

 shaking. 



Milk. Milk is slowly acidified and slowly coagulated. 

 This action is chiefly upon the casein ; very few, if any, changes 

 are produced either in the sugars or in the fats of the milk. 

 The acids formed are, according to Iwanow, 6 chiefly formic, 

 acetic, and caporic. 



Life conditions and properties. The anthrax bacterium 

 is aerobic and facultative anaerobic. In the animal body it 

 occasionally forms capsules. In artificial cultures in the pres- 

 ence of oxygen, it sooner or later invariably forms_spores. The 

 spores appear after the culture has reached its maximum of 

 development. Sporulation never occurs in the animal body, 

 probably because of the absence of sufficient free oxygen. 

 Spores are formed most extensively 7 at temperatures ranging 

 from 20 to 30 C. Spore formation ceases below 18 C. and 

 above 42 C. For different strains these figures may vary 

 slightly, as has been shown by the results of various observers. 

 Spores appear most rapidly and regularly upon agar and 

 potato media. 



If anthrax bacteria are cultivated for prolonged periods 

 upon media containing hydrochloric or rosalic acid or weak 

 solutions of carbolic acid, 8 cultures may be obtained which do 

 not develop spores and which seem permanently to have lost 

 the power to produce them without losing their virulence to 

 the same degree. Similar results may be obtained by continu- 

 ous cultivation at temperatures above 42 C. By this pro- 

 cedure, however, its virulence is diminished or entirely lost. 



Pathogenesis. Of the experimental animals, white and 

 field mice and guinea pigs are most susceptible. The Algerian 

 sheep shows a marked resistance, while the European variety 

 is highly susceptible. The gray rat is much more resistant 



6 Iwanow. Ann. de 1'Institut Pasteur, 1892. 

 T Koch, loc. cit. 



8 Chamberland et Roux. Compt rendu de 1'Acad. des Sci., VoL 

 XCVI (1882). 



