362 



SPECIFIC MICRO-ORGANISMS 



in surface waters but certain waters, as for example ttie Ganges 

 River, destroy the cholera spirilla very quickly. This property 

 has been ascribed to a weak acidity of the water. 



Fig. 141. — Cholera vibrios, longer forms at higher magnification, showing long 

 flagella. (From Kolle and Schiirmann after Zettnow.) 



Animals are not naturally susceptible to cholera. 'Koch gave 

 to a guinea-pig 5 c.c. of a 5 per cent solution of sodium carbonate 



• «. 



Pig, 142. — Involution forms of the spirillum of cholera. (Vo« Ermengem.) 



through a tube, and then 5 to 10 c.c. of water containing cholera 

 spirilla. The animal then received i c.c. of tincture of opium 



