476 PATHOGENIC MICROORGANISMS 



very severely, van Ermengem found the bacilli in large numbers lying 

 between the muscle fibers in the ham, and was able to cultivate the same 

 microorganism from the stomach and spleen of one of those who died of 

 the infection. 



The results of van Ermengem have been confirmed by Romer,' and 

 others. 



Morphology and Staining. — Bacillus botulinus is a large, straight rod 

 with rounded ends, 4 to 6 micra in length by 0.9 to 1.2 micra in thickness. 

 The bacilli are either single or grouped in very short chains. Involu- 

 tion forms are numerous on artificial media. The bacillus is slightly 

 motile and possesses from four to eight undulated flagella, peripherally 

 arranged. Spores are formed in suitable media, most regularly in 

 glucose-gelatin of a distinctly alkaline titer. The spores are oval and 

 usually situated near the end of the bacillus, rarely in its center. Spores 

 are formed most abundantly when cultivation is carried out at 20° 

 to 25° C, and are usually absent when higher temperatures are em- 

 ployed. 



The bacillus is easily stained by the usual aqueous anilin dyes, and 

 retains the anilin-gentian- violet when stained by Gram. It is necessary, 

 however, in carrying out Gram's stain to decolorize carefully with alco- 

 hol since overdecolorization is easily accomplished, leaving the result 

 doubtful. 



Cultivation. — The bacillus is a strict anaerobe. In anaerobic en- 

 vironment it is easily cultivated on the usual meat-infusion media. It 

 grows most readily at temperatures about 25° C, less luxuriantly at 

 temperatures of 35° C. and over. 



The bacillus is delicately susceptible to the reaction of media, 

 growing only in those which are neutral or moderately alkaline. 



In deep stab cultures in one per cent glucose agar, growth is at first 

 noticed as a thin, white column, not reaching to the surface of the 

 medium. Soon the medium is cracked and split by the abimdant 

 formation of gas. On agar plates, the colonies are yellowish, opalescent, 

 and round, and show a finely fringed periphery. 



On gelatin, at 20° to 25° C, growth is rapid and abundant, and 

 differs little from that on agar, except that, besides the formation of 

 gas, there is energetic fluidification of the medium. On glucose-gelatin 

 plates, van Ermengem describes the colonies as round, yellowish, 

 transparent, and composed of coarse granules which, along the periphery 



> Bomer, Cent. f. Bakt., xxvii, 1900. 



