BACTERIA AND ICE 163 



ture of liquid air. The specimens of the con- 

 sumption bacillus employed were originally 

 obtained from the human subject, and they 

 were exposed for periods varying from six hours 

 to six weeks to - 190 C. In each case the 

 malignant properties of the tubercle bacillus after 

 exposure were tested by their direct inoculation 

 into animals, and the results compared with those 

 which followed similar inoculations made with 

 bacilli which had not been frozen in this manner, 

 but had been grown in ordinary circumstances. 

 In no single case, Mr. Swithinbank tells us, were 

 these frozen tubercle bacilli deprived of their 

 "virulence, and the length of exposure, at any rate 

 as far as could be judged after six weeks, appeared 

 to make no difference in this respect. It is true 

 that the pathogenic action of the frozen bacilli 

 appeared to be somewhat retarded that is, they 

 took rather longer to kill animals than the ordinary 

 unfrozen bacilli but in every case their inoculation 

 produced the typical tuberculous lesions associated 

 with them. 



Of particular interest, however, in view of what 

 has been already discovered about the lethal effect 

 upon bacteria of violent alternations of tempera- 

 ture, are Mr. Swithinbank's observations on the 

 vitality of the tubercle bacillus when exposed to 

 such extreme variations of temperature as are 



