I 90 BACTERIA 



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On gelatine plates, the colonies appear first as minute white 

 specks, which slowly liquefy the medium. As it grows, hair-like 

 threads branch out into the medium, and the colony resembles 

 the periphery of a chestnut burr; later, the white appearance 

 changes to yellow. In gelatine stab the growth is, at first, 

 whitish along the line of the needle, eventually the gelatine 

 becomes liquid, and a bubble of gas, partly filled with whitish- 

 cloudy liquid gelatine, appears. On agar plates the colonies are 

 ragged, and are surrounded by delicate out-spreading filaments. 

 In deep stab culture, down in the agar and remote from the top, 

 a spreading tree-like form appears, with spike-like growths in the 

 agar. Blood serum is sometimes liquefied. Bouillon is uniformly 

 clouded, gas is generated if sugar is present, and toxin is produced. 

 Milk is, generally, not coagulated. 



All cultures of tetanus must be grown under an atmosphere of 

 hydrogen in media, from which all free 

 oxygen has been driven by boiling, or else 

 abstracted by a mixture of pyrogallic acid 

 and sodium hydrate. It is possible to culti- 

 vate the organism under mica covering, or 

 paraffine poured upon freshly boiled media. 

 If sterile glass tubing is filled, with agar or 

 JT IG rr Tetanus g e l atme > an d inoculated with tetanus bacilli, 

 bacilli showing peri- then sealed, colonies will develop, as perfect 



ril?u. U S w gdla ' anaerobic conditions are thus obtained. 

 (Kolle and Wasser- 



mann.) Often the organism grows best m the pres- 



ence of saprophytic ones. Strongly patho- 

 genic organisms do not grow well in culture media, while com- 

 paratively non- virulent ones grow very well. 



Pathogenesis. Tetanus may follow any wound, no matter how 

 insignificant, though deeply punctured ones, caused by nails or 

 splinters, are more often followed by tetanus infection, especially 

 if the puncture is sealed by blood clots or pus, and so creating an 

 anaerobic condition necessary for growth. If the wound is on the 



