VIRULENT DISEASES. 189 



Pasteur, in obedience to the necessity he felt to get at 

 the fundamental truth of things, and also in his eager 

 desire to discover some decisive proofs as to the 

 etiology of this terrible disease, resolved in his turn 

 to attack the subject. 



Dr. Koch had stated in his memoir that the little 

 filiform bodies, seen for the first time by Davaine in 

 1850, had two modes of reproduction one by fission, 

 which Davaine had observed, and another by bright 

 corpuscles or spores. The existence of this latter 

 mode of reproduction Pasteur had already discovered 

 in 1865, reasserted and illustrated in 1870, as being 

 common to the filaments of the butyric ferment, and 

 to all the ferments of putrefaction. Was Dr. Koch 

 ignorant of this important fact, or did he prefer by 

 keeping silence to reserve to himself the advantage of 

 apparent priority ? 



In order to solve the first difficulty which pre- 

 sented itself to his mind that is to say, the question 

 as to whether splenic fever was to be attributed to a 

 substance, solid or liquid, associated or not associated 

 with the filaments discovered by Davaine, or whether it 

 depended exclusively upon the presence and the life of 

 these filaments Pasteur had recourse to the methods 

 which for twenty years had served him as guides 

 in his studies on the organisms of fermentation. 

 These methods, delicate as they are, are very simple. 

 When he wished, for example, to demonstrate that the 



