218 LOUIS PASTEUR. 



spects from the parasite of splenic fever. If splenic 

 fever blood filled with filaments of the parasite be 

 enclosed in a vessel protected from the air say, in a 

 tube closed at its two extremities in a few days, eight 

 or ten at the most, and much fewer in summer, the 

 parasite disappears, or rather is reduced to fine amor- 

 phous granulations, and the blood loses all its viru- 

 lence. If the same system of shutting out the air be 

 employed with the blood of a fowl charged with the 

 microbe of fowl cholera, this microbe will be preserved 

 with its virulence for w r eeks, months, even years. 

 Pasteur has been able to keep for three years tubes 

 thus sealed, a drop of blood from which when culti- 

 vated in fowl infusion, sufficed to infect the birds in 

 the poultry yard with cholera. And not only is the 

 microbe preserved thus in the blood contained in the 

 tube; the same occurs if fowl infusion be put into 

 tubes and then sealed by the flame of a lamp. 



When, in course of time, such tubes lose their 

 virulence, it is because the vitality of the organism is 

 extinct. The moment the contents of the tube cease 

 to be virulent, it is a sign that the contagium is di-ad. 

 It is useless, then, to attempt to cultivate it : the 

 microbe cannot be revived. 



Here, then, is a third virulent disease, also produced 

 by a microscopic organism. The characteristics of fowl 

 cholera are very different from those of splenic fever 

 and acute septicernia, and these three microbes do not 



