Vital Resistance 453 



gelatin is followed by the formation of considerable sediment 

 in the lower third or 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, but is not complete for several weeks. 



Agar-agar. When planted upon the surface of agar- 

 agar the spirilla produce a grayish-white, shining, translu- 

 cent growth along the entire line of inoculation. It is in 

 no way peculiar or characteristic. 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. 



Blood-serum. The growth upon blood-serum is also 

 without distinct peculiarities; gradual liquefaction of the 

 medium occurs. 



Potato. Upon potato the spirilla grow well, even when 

 the reaction is acid. In the incubator, at a temperature of 

 37 C., a transparent, slightly brownish or yellowish-brown 

 growth, somewhat resembling that of glanders, is produced. 

 It contains large numbers of long spirals. 



Bouillon. In bouillon and in peptone solution the 

 cholera organisms grow well, especially upon the surface, 

 where a folded, wrinkled pellicle is formed, the culture 

 fluid remaining clear. 



Milk. In milk the growth is luxuriant, but does 

 not visibly alter its appearance. The existence of cholera 

 organisms in milk is, however, rather short-lived, for the 

 occurrence of acidity at once destroys them. 



Vital Resistance. Although an organism that multiplies 

 with great rapidity under proper conditions, the cholera 

 spirillum does not possess much resisting power. Stern- 

 berg found that it was killed by exposure to 52 C. for 

 four minutes, but Kitasato found that ten or fifteen 

 minutes' exposure to 55 C. was not always fatal to it. In 

 a moist condition the organism may retain its vitality for 

 months, but it is very quickly destroyed by desiccation, as 

 was- found by Koch, who observed that when dried in a thin 

 film its power to grow was destroyed in a few hours. Kita- 

 sato found that upon silk threads the vitality might be 

 retained longer. Abel and Claussen * have shown that it 



* "Centralbl. f. Bakt. u. Parasitenk.," Jan. 31, 1895, vol. xvn, No. 4. 



