3 i8 PATHOGENIC BACTERIA. 



The luxuriant development of the spirilla in gelatin 

 produces considerable solid material to sediment and fill 

 up the lower third or lower half of the liquefied area. 

 This solid material consists of masses of spirilla which 

 have probably completed their life-cycle and become 

 inactive. Under the microscope they exhibit the most 

 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 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 37 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- 



