THE LABORATOEY OF THE ECOLE NORMALS. 293 



healthy adults. It was a new microbe, causing a 

 disease unknown up to that time. To Pasteur it 

 seemed, in the case of the experiments made with the 

 mucus from the child's palate, to be simply an ac- 

 companiment of the rabic virus. 



This microbe of the saliva is very easily cultivated 

 in sterile infusions that of veal, for example and 

 successive cultures can be made in the usual way. 

 The virulence continues. Could the virulence be at- 

 tenuated, asked Pasteur, by the action of the oxygen of 

 the air ? This would, by a new example, go to esta- 

 blish the generalisation of the method of attenuation by 

 oxygen. The attempt succeeded. When care is taken, 

 as with the attenuation of the fowl cholera contagium, 

 not to allow more than some hours' interval to elapse 

 between one cultivation and the succeeding one, the 

 virulence of the successive cultivations of the microbe 

 of the saliva is preserved in some sort indefinitely. In 

 other words, if it be arranged that the cultures succeed 

 each other every twelve hours, the rabbits inoculated 

 from the last cultures die as quickly as those inocu- 

 lated from the first. Thuillier had had the patience 

 to make, in this manner, eighty cultures in contact 

 with air, and eighty cultures in a vacuum ; the mi- 

 crobe of the saliva being both aerobic and anaerobic. 

 The eightieth culture killed as quickly as the first. 

 But by allowing the successive cultures to remain for 



