THE ANAEROBIC BACILLI 729 



organism with especial frequency, probably because of its presence 

 in the dejecta of some of the domestic animals. 



Biological Characteristics. The bacillus of tetanus is generally 

 described as an obligatory anaerobe. While it is unquestionably 

 true that growth is ordinarily obtained only in the complete absence 

 of oxygen, various observers, notably Ferran 5 and Belfanti, 6 have 

 successfully habituated the bacillus to aerobic conditions by the 

 gradual increase of oxygen in cultures. Habituation to aerobic con- 

 ditions has usually been accompanied by diminution or loss of 

 pathogenicity and toxin-formation. Anaerobic conditions may like- 

 wise be dispensed with if tetanus bacilli be grown in symbiosis with 

 some of the aerobic bacteria. The addition to culture media of suit- 

 able carbohydrates, and of fresh sterile tissue, has also been found to 

 render it less exacting as to mechanical anaerobiosis. 7 



Anaerobically cultivated, Bacillus tetani grows readily upon meat- 

 infusion broth, which it clouds within twenty-four to thirty-six hours. 



Upon meat-infusion gelatin at 20 to 22 C. the tetanus bacillus 

 grows readily, growth becoming visible during the second or third 

 day. There is slow liquefaction of the gelatin. 



On agar, at 37.5 C., growth appears within forty-eight hours. 

 Colonies on agar. plates present a rather characteristic appearance, 

 consisting of a compact] center surrounded by a loose mesh work of 

 fine filaments, not unlike the medusa-head appearance of subtilis 

 colonies. In agar stabs, fine radiating processes growing out in all 

 directions from the -central stab tend to give the culture the appear- 

 ance of a fluff of cotton. Milk is a favorable culture medium and is 

 not coagulated. On potato, growth is delicate and hardly visible. 



The most favorable temperature for the growth of this bacillus 

 is 37.5 C. Slight alkalinity or neutrality of the culture media is 

 most advantageous, though moderate acidity does not altogether 

 inhibit growth. All the media named may be rendered more favor- 

 able still by the addition of one or two per cent of glucose, maltose, 

 or sodium formate. 8 In media containing certain carbohydrates, 

 tetanus bacilli produce acid. In gelatin and agar, moderate amounts 

 of gas are produced, consisting chiefly of C0 2 , 9 but with the admix- 



5 Ferran, Cent. f. Bakt., xxiv, No. 1. 



6 Belfanti, Arch, per le sci. med., xvi. 



7 Th. Smith, Brown, and Walker, Jour. Med. Res., N. S., ix, 1906. 



8 Kitasato, Ztschr. f. Hyg. 1891. 



9 v. Eisler and Pribram in Kraus and Levaditi, Handbuch, etc., Jena, 1907, 



