Vital Resistance 631 



teristic of the bacillus are formed with exceptional rapidity. 

 In bouillon containing this high percentage of salt the stalac- 

 tite formation is beautiful and characteristic. 



Blood-serum. Upon blood-serum growth at the tem- 

 perature of the incubator is luxuriant and forms a moist 

 layer, of a yellowish-gray color, unaccompanied by lique- 

 faction of the serum. 



Potato. Upon potato no growth occurs at ordinary 

 temperatures. When the potato is stood in the incubator 

 for a few days, a scanty, dry, whitish layer develops. 



Abel found the best culture medium to be 2 per cent, alka- 

 line peptone solution containing i or 2 per cent, of gelatin, 

 as recommended by Yersin and Wilson. 



Vital Resistance. Kitasato found that the plague 

 bacillus did not seem able to withstand desiccation longer 

 than four days ; but Rappaport * found that they remained 

 alive when kept dry upon woolen threads at 20 C. for 

 twenty-three days, and Yersin found that although it could 

 be secured from the soil beneath an infected house at a depth 

 of 4-5 cm., the virulence of such bacilli was lost. 



Kitasato found that the bacillus was killed by two hours' 

 exposure to 0.5 per cent, carbolic acid, and also by exposure 

 to a temperature of 80 C. for five minutes. Ogata found 

 the bacillus instantly killed by 5 per cent, carbolic acid, and 

 in fifteen minutes by 0.5 per cent, carbolic acid. In o.i per 

 cent, sublimate solution it is killed in five minutes. 



According to Wyman,' the bacillus is killed by exposure 

 to 55 C. for ten minutes. The German Plague Commission 

 found that the bacilli were killed by exposure to direct sun- 

 light for three or four hours ; and Bowhill f found that they 

 are killed by drying at ordinary room temperatures in about 

 four days. 



Wilson t found the thermal death- point of the organism 

 one or two degrees higher than that of the majority of non- 

 sporulating pathogenic bacteria, and that the influence of 

 sunlight and desiccation cannot be relied upon to destroy it. 



Rosenau found temperature the most important factor, 



* Quoted by Wyman. 



t "Manual of Bacteriological Technique and Special Bacteriology," 

 1899, p. 197. 



t "Journal of Medical Research," vol. vi, No. 1, p. 53, July, 1901. 



Bulletin No. 4 of the Hygienic Laboratory of the U. S. Marine 

 Hospital Service, 1901. 



