140 Chapter VI 



develop fairly luxuriantly at the low temperature of 12 C. Under 

 these conditions all the inoculated frogs, even those which had 

 resisted the inoculation with ordinary bacteria (grown at 37'5 C.), 

 died within a period of 48 to 56 hours, containing many bacilli in 

 the blood and organs. Dieudonn^ has not studied the essential 

 mechanism that accompanies this loss of immunity; but it is very 

 probable that, for one thing, we have here to do with a reinforcement, 

 special for the frog, of the bacillus that has become accustomed 

 to develop at a low temperature. This bacillus must multiply, in 

 frogs that have been maintained at a low temperature, much more 

 rapidly and profusely than would the ordinary bacillus. On the other 

 hand, the susceptibility of Dieudonne"'s frogs must depend on a less 

 resistance of the organism under the conditions of his experiments. 

 Unfortunately, we cannot find in his memoir sufficient data on these 

 points; he does not even state the temperature at which the frogs 

 that had been inoculated with bacteria adapted to cold lived. 

 Dieudonne invokes the analogy of his results with those obtained 

 [149] in the case of the immunity and susceptibility of frogs as regards 

 a septicaemic bacillus. 



This bacillus (Bacillus ranicida) has been made the subject of 

 an interesting study by Ernst 1 . It is a small, very slender bacillus, 

 which, in frogs, produces a fatal malady epidemic in spring, but 

 ceasing completely during summer. Taking this fact as a basis, 

 Ernst has succeeded in conferring immunity upon frogs in autumn 

 by placing them in an incubator at 25 C. In spite of the injection 

 of a considerable dose of the small bacillus, the frogs living at this 

 temperature remained in good health, whilst control animals exposed 

 to a low temperature died of septicaemia. The counter-test was 

 made in summer. Inoculated frogs that were kept in the laboratory 

 were unaffected, whilst those that had been kept in a refrigerating 

 apparatus at 6 10 C. invariably died. It may be asked, Is this 

 evident influence of temperature on immunity and receptivity exer- 

 cised on the organism of the frog or upon the pathogenic bacillus ? 

 In the case where a bacillus can only develop at low temperatures 

 its harmlessness at the higher temperature may be readily under- 

 stood. The experiments of Ernst have demonstrated, however, that 

 this small bacillus develops much better at 22 C., and even at 30 C., 

 than at lower temperatures. It must be concluded, therefore, 

 that the high temperature which confers immunity acts not by 

 1 Zieglers Beitr. z.path. Anat., Jena, 1890, Bd. vra, S. 203. 



