FOWL CHOLEBA. 213 



a professor of the veterinary school of Toulouse, M. 

 Toussaint, recognised it, in his turn, in 1879, and sent 

 to Pasteur the head of a cock which had died of 

 the cholera. But, however skilful they were, these 

 observers had not succeeded in deciding the question 

 of parasitism. None of them had hit upon a suitable 

 cultivating medium for the parasite, nor had they 

 reared it in successive crops. This, however, is the 

 only method of proving that the virulence belongs 

 exclusively to a parasite. 



It is absolutely necessary, in the study of maladies 

 caused by microscopic organisms, to procure a liquid 

 where the infectious parasite can grow and multiply 

 without possible mixture of other organisms of differ- 

 ent kinds. An infusion of the muscles of the fowl, 

 neutralised by potash, and rendered sterile by a tem- 

 perature of 110 to 115 degrees, has proved to be 

 wonderfully appropriate to the culture of the microbe 

 of fowl cholera. The facility of its multiplication in 

 this medium is almost miraculous. In some hours 

 the clearest infusion begins to grow turbid, and is 

 found to be filled with a multitude of little organisms 

 of an extreme tenuity slightly strangulated at their 

 centres. These organisms have no movement of their 

 own. In some days they change into a multitude 

 of isolated specks, so diminished in volume that the 

 liquid, which had been turbid to the extent of resembling 

 milk, becomes again almost as clear as at first. The 



