BIOLOGICAL PROPERTIES 565 



of salt. Leave the mixture in the ice-chest for 12 or 20 hours. Decant the liquid 

 and squeeze the residue in a meat press. Add normal soda solution until the reac- 

 tion of the fluid is feebly alkaline then heat to 115 C. for 5 minutes. Filter through 

 Chardin paper and sterilize the dark brown filtrate at 112 C. for 20 minutes. A 

 slight coagulum forms during sterilization but dissolves during the growth of the 

 organism. 



Gelatin. Deep stab culture. At 20 C. growth begins after incubating 

 about 48 hours. Small cloudy spheres appear along the line of the stab and 

 these rapidly become confluent forming a long, whitish streak. Bubbles of 

 gas then appear which split the gelatin and the culture spreads irregularly 

 along these fissures. Liquefaction rapidly follows and involves the whole 

 of the medium. 



Single colonies. On the second or third day small cloudy whitish spots 

 with ill-defined margins appear in the depth of the medium. The medium 

 liquefies around them and bubbles of gas are. formed. 



Agar. Deep stab culture. Growth in the form of a cloudy whitish streak 

 along the line of the stab very quickly appears on incubating at 37 C. The 

 agar is soon split by bubbles of gas and the culture spreads along the fissures. 



Potato. No apparent growth. 



Coagulated serum. The bacillus grows and liquefies the serum. Cooked 

 white of egg is also digested by the bacillus. 



SECTION III. BIOLOGICAL PROPERTIES. 

 1. Vitality and virulence. 



Vitality. Bacilli which are not in the spore condition are soon killed by 

 exposure to air or by heating for a few moments at 60 C. 



Spores are only formed in the complete absence of air but once formed 

 they are highly resistant to the action of oxygen. Ordinary antiseptic 

 solutions are almost without action upon them (Chauveau and Arloing). 

 In the moist state they resist temperatures of 80 C. for several hours and 

 90 C. for more than 30 minutes (Besson). They are only killed by moist 

 heat above 100 C. when contained in dried albuminous material. According 

 to Sanfelice they are not affected by exposure to sunlight for 50 hours nor 

 by desiccation extending over several months. 



Virulence. The virulence of the organism is preserved by the spore : this 

 virulence is maintained indefinitely in cultures, but for purposes of inocula- 

 tion it is always necessary to make a new sub-culture, since the spores alone 

 in ordinary doses are harmless and the toxin is weakened by keeping (infra). 

 If this precaution be not observed the organism may be erroneously thought 

 to have become attenuated. 



All strains of the bacillus are not equally virulent : some are non- virulent 

 even for guinea-pigs (vide ante], but as has already been pointed out these 

 variations are not stable, for the virulence of a slightly virulent bacillus 

 may be easily raised by passage through guinea-pigs. 



Leclainche and Vallee have shown that the method of attenuation by heat devised 

 by Arloing, Cornevin and Thomas for the bacillus of quarter ill (Chap. XXXVII. ), is 

 equally applicable to this bacillus. Heat the blood of an animal dead of malignant 

 oedema in sealed ampoules at 37 C. for 5 days and treat the contents of the ampoules 

 by Arloing's method (p. 556). The resulting powder constitutes an attenuated virus 

 with which animals may be immunized against the disease. 



2. Toxin. 



(i) As early as 1887 Eoux and Chamberland studied the toxin which the 

 bacillus produces in cultures and in the living organism. 



