272 PASTEUR: THE HISTORY OF A MIND 



an inoculated chicken some degrees? The success of 

 the experiment was immediate. A chicken, the feet 

 and hind quarters of which were plunged into water at 

 25 C, so that the temperature of its whole body was 

 lowered to 37-38"^ C, which is the temperature of animals 

 susceptible to anthrax, died of this disease, although 

 resistant to it under normal conditions. If the chicken 

 is taken from the water and heated at the time when 

 the first symptoms of invasion of the tissues appear, 

 it triumphs over all the parasites and recovers. Later 

 Gibier made the reverse experiment, giving anthrax 

 to frogs which are not susceptible to this disease because 

 they are cold-blooded animals, the body temperature 

 being too low. To accustom them little by little to 

 living in warm water, suffices to render them capable 

 of succumbing to anthrax when their body temperature 

 has been thus raised. The interpretation of these two 

 facts is less simple then Pasteur supposed it to be and 

 we shall meet them again very soon in connection with 

 variations in virulence. I cite them only as further 

 evidence of his tendency to relegate everything as much 

 as possible to the domain of physics and chemistry, 

 to study, in the light of these two sciences, the physio- 

 logical properties of the microbe and to oppose these 

 properties to those of the tissues. 



However broad-minded one may be, he is always 

 to some extent the slave of his education and of his past. 

 It is clear that Pasteur inclined naturally to the side 

 of chemistry, and there were not lacking men to reproach 

 him for this. To this chiding he always disdained to 

 respond. Doubtless he thought it was not worth while, 

 and that he must be content to pity those who believed it 

 possible for a vital problem to be something other than a 

 problem of physics and chemistry. This will be still more 

 evident in the study which we shall make of virulence. 



