386 PHARMACEUTICAL BACTERIOLOGY 



Rats (bearing the infected fleas) are the principal carriers of this 

 disease, and the experience in San Francisco (1906-1909) has demonstrated 

 that plague disappears as soon as the plague infested rats disappear. De- 

 stroy rats and mice and see to it that the home is free from fleas. Plague 

 is a quarantinable disease and the federal authorities are constantly on 

 the lookout to prevent the importation of this disease. The Oriental 

 ports are the chief sources of infection. 



Yersin's anti-plague serum and Haffkine's bacterin have been used with 

 considerable success as prophylactics and also with some success as cures. 



I. Asiatic Cholera. This is another filth disease essentially of Oriental 

 origin, particulaly prevalent in the crowded unsanitary cities of India 

 and Asia. It is a quarantinable disease. The primary cause is the non- 

 sporogenous Bacillus cholera (Spirillum cholera) also known as the 

 comma bacillus of Koch. The principal sources of the infection are pol- 

 luted water and food, particularly the former. In fact the sources of in- 

 fection and modes of entry into the digestive tract are not unlike those 

 of typhoid. Cholera is highly infectious and usually occurs epidemically, 

 often spreading over wide areas. Human excrement carries the infection 

 and when this material is used as fertilizer, which is done in China and 

 other Oriental countries, it becomes the means of initiating and continuing 

 the spread of the disease. The importing by the Chinese of human ex- 

 crement and animal dung for medicinal purpose should be prohibited 

 as it may be the means of starting an epidemic of cholera in the United 

 States, even though it is unlikely that the infection will survive 

 the trip. 



Fortunately the cholera bacillus is easily killed by heat, disinfectants, 

 and by drying. The temperature of boiling water kills it in five minutes. 

 In water it may retain its vitality for a long time. Furthermore, it is not 

 a strict (obligative) parasite and may multiply outside of the body under 

 favorable conditions. Flies carry the infection from cholera stools to 

 articles of food. 



Haffkine's attenuated cholera bacterin has been employed successfully 

 as a prophylactic. The method of use consists first in the hypodermic in- 

 jection of a weak virus, that is, cultures attenuated by long cultivation at a 

 high temperature (39 C)., and following this later, in five days, with a 

 virulent culture. More recently Kolle has used cultures killed by heating 

 for one hour at 58 C., which has given good results in numerous tests made 

 during a cholera epidemic in Japan. Pf eiffer and others have experimented 

 extensively with cholera-immune serum and have demonstrated that this 

 has marked lyctic properties. The cholera bacilli when placed into the 

 serum first lose motility, then swell up into coccus-like forms and finally 

 dissolve. This property is said to be due to two substances, one found in 



