ACTION OF HEAT 309 



Bulloch and Macleod l state that the acid-fast substance 

 of the tubercle bacillus is an alcohol. Hot xylol will 

 remove this substance from the tubercle bacillus, and 

 ether or 5 per cent, caustic soda that from the smegma 

 bacillus ; the organisms after this treatment are no longer 

 " acid-fast." 



Maragliano states that toxic bodies are present in the 

 blood and urine of tuberculous individuals. Cellulose also 

 seems to be present in small amount in the bacilli (it has 

 also been found in tuberculous nodules). 



Tubercle bacilli, living or dead, are with great difficulty 

 absorbed when in any quantity. The dead bacilli when 

 injected under the skin invariably cause suppuration, and 

 several months later it is still possible to detect in the pus 

 numerous bacilli which stain well ; introduced into the 

 circulation of rabbits they give rise to nodules in the lungs 

 similar to the tuberculous nodules produced by living 

 bacilli (Koch). 



Action of heat and antiseptics on the tubercle bacillus. 

 The thermal death-point of the bacillus has been the 

 subject of some controversy. Sternberg found that tuber- 

 culous sputum exposed for ten minutes to a temperature 

 of 90, 80, and 66 C. failed to infect guinea-pigs in inocu- 

 lation, while another specimen of the same sputum heated 

 for ten minutes to a temperature of 50 C. produced tuber- 

 culosis in a guinea-pig, so that from these experiments the 

 thermal death-point lies between 50 and 66 C. 



Yersin in 1888, by culture methods, failed to obtain 

 any growth from bacilli which had been heated to 70 C. 

 for ten minutes, while those heated to 55 C. and 60 C. 

 gave growths in glycerin broth in ten days and twenty-two 

 days respectively. Macfadyen and the writer, in the 

 course of some experiments on the sterilisation of milk 

 found that milk to which powdered dried sputum had been 



1 Journ. of Hygiene, vol. iv, 1904, p. 1. 



