428 PATHOGENIC BACTERIA. 



varied involution-forms. The liquefaction reaches the 

 sides of the tube in from five to seven days. Liquefac- 

 tion of the medium is not complete for several weeks. 

 According to Frankel, in eight weeks the organisms in 

 the liquefied culture all die, and cannot be transplanted. 

 Kitasato, however, has found them living and active on 

 agar-agar after ten to thirty days, and Koch was able 

 to demonstrate their vitality after two years. 



When planted upon the surface of agar-agar the spi- 

 rilla produce a grayish-white, shining, translucent growth 

 along the entire line of inoculation. It is in no way 

 peculiar. The vitality of the organism is retained much 

 better upon agar-agar than upon gelatin, and, according 

 to Frankel, the organism can be transplanted and grown 

 when nine months old. 



The growth upon blood-serum likewise is without dis- 

 tinct peculiarities, and causes gradual liquefaction of the 

 medium. 



Upon potato the spirilla grow well, even when the 

 reaction of the potato is acid. In the incubator at a 

 temperature of ^7° C. a transparent, slightly brownish 

 or yellowish-brown growth, somewhat resembling the 

 growth of glanders, is produced. It contains large 

 numbers of long spirals. 



In bouillon and in peptone solution the cholera organ- 

 isms grow well, especially upon the surface, where a 

 folded, wrinkled mycoderma is formed. Below the my- 

 coderma the culture fluid generally remains clear. If 

 the glass be shaken and the mycoderma broken up, 

 fragments of it sink to the bottom. 



In milk the development is also luxuriant, but takes 

 place in such a manner as not visibly to alter its appear- 

 ance. The existence of cholera organisms in milk is, 

 however, rather short-lived, for the occurrence of any 

 acidity at once destroys them. 



Wolffhugel and Riedel have shown that if the spirilla 

 are planted in sterilized water they grow with great ra- 

 pidity after a short time, and can be found alive after 



