498 Mr. H. Swithinbank. Effect of Exposure to 



of the commencement of the experiment. I can only attribute this 

 immunity to a very high degree of natural resistance which at times is 

 met with in all experimental animals, and which we are compelled to 

 allow for. 



Eighteen animals were born during the course of the experiment, at 

 intervals of 4, 5, 9, and 13 weeks, all of whose parents subsequently 

 were found to be tuberculous. These were killed and examined at 

 intervals, and in not one of them was there evidence of tuberculosis. 

 It would therefore be not unreasonable to suppose that, although 

 desiccation for a period of fourteen days proved insufficient to destroy, 

 under these conditions, the virulence of the sputum, yet this was 

 accomplished at some point between this and four weeks. What this 

 point is, a further experiment on similar lines when sufficient sunlight 

 is available, will be necessary to elucidate. I propose to carry this out 

 in the early summer of next year. 



" Effect of Exposure to Liquid Air upon the Vitality and Viru- 

 lence of the Bacillus Tuberculosis." By H. Swithinbank. 

 Communicated by Sir James Crichton Browne, E.B.S. 

 Eeceived June 11, — Eead June 20, 1901. 



A series of experiments carried out early in the year 1900 with 

 the object of testing the effect of the temperature of liquid air upon 

 the vitality and virulence of the bacillus tuberculosis produced results 

 which, although in complete accord as far as the question of vitality 

 was concerned with those arrived at by Professor Macfadyen in the 

 carefully planned experiments reported to the Eoyal Society on the 

 1st February and the 5th April, 1900, raised some doubt in my mind 

 as to whether the abnormally low temperature, continued for a 

 lengthened period, might not have some modifying effect upon the 

 virulence of the organism. I decided therefore, in the month of 

 January of this year, to put the question to the test of an experi- 

 ment which I hoped would be conclusive. 



The questions to be solved appeared to me to be — 



1. Whether exposure for varying periods to the temperature of 

 liquid air had any effect upon the vitality of the bacillus tuberculosis. 



2. Whether such exposure in any way modified its virulence. 



3. Whether time was a factor in the question. 



4. Whether, as is the case at the higher end of the thermometric 

 scale, successive alternations of temperature had any special effect. 



5. Whether actual contact* with liquid air, if obtainable, produced 

 any special results. 



# The word "contact" is used throughout, but it is doubtful whether actual 



