388 APPLICATION OF METHODS OF BACTERIOLOGY 



It grows best at a temperature of from 35° to 38° C. Below 

 24° C. there is usually no development, but in a few cases 

 it has been seen to grow at as low a temperature as 18° C. 

 Above 42° C. development is checked. 



It grows as well without as with oxygen. It is therefore 

 one of the facultative anaerobic forms. 



Cultivation of this organism is most successful when 

 some one of the serum-agar or agar-gelatin mixtures is 

 employed. (See the medium.) 



It may be stained with the ordinary aniline staining- 

 reagents. For demonstrating the capsule the method of 

 Gram and the acetic-acid method give the best results. 

 (See Stainings.) 



This organism is conspicuous for the irregularity of its 

 behavior when grown under artificial conditions: usually it 

 loses its pathogenic properties after a few generations; but 

 again this peculiarity may be retained for a much longer 

 time. Often it fails to grow after three or four trans- 

 plantations on artificial media, though at times it may be 

 carried through many generations. 



Inoculation into Animals. — ^The results of inoculations with 

 pure cultures of this organism are also conspicuous for their 

 irregularity. When the organism is of full virulence the 

 form of septicemia above described is usually produced, but 

 at times it is found to be totally devoid of pathogenic powers : 

 between these extremes cultures may be obtained possess- 

 ing every variation in the intensity of their disease-produc- 

 ing properties. The principal pathological conditions that 

 may be produced by the inoculation of susceptible animals 

 with this organism are, according to the degree of its viru- 

 lence, acute septicemia, spreading inflammatory exudations, 

 and circumscribed abscesses. All three of these conditions 



