96 MICRO-ORGANISMS AND DISEASE [chap. 



in half a minute, those of bacillus subtilis (hay bacillus) are 

 not killed at this temperature in less than five to seven 

 minutes, and some spores (in some species of bacillus mes- 

 entericus) require ten and even fifteen minutes' exposure. 



Owing to the great resistance of spores to heat it is possible 

 and is easy in a mixture of non-sporing and sporing bacilli 

 to separate the former from the latter, by subjecting the fluid 

 containing the mixture to a temperature of 70° C. for five or 

 ten minutes, here by all non-sporing forms are killed whereas 

 the spores remain unharmed, and cultures made from the so 

 heated mixture produce growths of the spores only. 



I will take a case in point. If a guinea-pig be injected 

 subcutaneously in the groin with a fair quantity of recently 

 manured garden earth, it dies as a rule in twenty-four to 

 thirty-six hours from Koch's malignant oedema ; the mal- 

 odorous sanguineous fluid in the subcutaneous tissue of the 

 groin, thigh, abdomen, and chest contains large numbers of 

 motile and non-motile bacilh, some of these latter contain- 

 ing bright oval spores ; the fluid is collected in a sterile 

 test-tube and this is kept exposed for ten minutes to a tem- 

 perature of 70° C, then anaerobic cultures are made in 

 grape sugar gelatine by deep inoculation. The tubes are 

 then sealed and incubated at 20° C. The growth that 

 makes its appearance now is a pure growth of the anaerobic, 

 liquefying bacillus of Koch's malignant oedema. But if 

 a culture be made with the subcutaneous fluid not heated, 

 generally only a copious growth of a bacillus similar to the 

 bacillus coli is produced, at best an abundance of the latter 

 and a very scarce growth of the former (Koch's malignant 

 oedema) is produced. And the same method of separating 

 the spores of any other microbe : anthrax, symptomatic 

 anthrax, tetanus bacillus, butyricus from a non-sporing 

 microbe that happened to be coexistent in a given material: 



