126 THE ACUTE SELF-LIMITED INFECTIONS 



but does not clot milk. It resists 60 C. or 142 F. for one 

 hour, but boiling kills at once. It multiplies at the tempera- 

 ture of foodstuffs, and freezing does not destroy it under three 

 days. Drying kills certainly in twenty-four hours in diffuse 

 light. Sunlight kills within one hour. The figures indicate 

 some resistance to heat and light, but against chemicals this 

 is not maintained; 1 to 10GO bichloride is fatal in ten minutes; 

 1 per cent, carbolic acid a little longer; lime in any form is 

 rapidly fatal to the spirillum. 



FIG. 38. Spirillum of Asiatic cholera: /, stained by ordinary method; 

 //, stained to show flagella. (Abbott.) 



Animals do not contract cholera either spontaneously or 

 artificially, but they may be killed by the germs or their 

 poisons. The active acquired immunity they get by repeated 

 injections has been described. It has not been found practical 

 to obtain any serum from animals which can be injected into 

 human beings as a treatment. Dead spirilla, however, can 

 be injected into well persons as a protective measure, 

 precisely as is done for typhoid and plague, and with good 

 results. 



