VIRULENT DISEASES. 181 



him to go forward. In February 1876 Tyndall wrote 

 to him thus : 



' In taking up your researches relating to infusorial 

 organisms, I have had occasion to refresh my memory 

 of your labours ; they have revived in me all the ad- 

 miration which I felt on first reading them. It is my 

 intention to follow up these researches until I shall 

 have dissipated every doubt that has been raised as to 

 the unassailable exactitude of your conclusions. 



' For the first time in the history of science we are 

 able to entertain the sure and certain hope that, in 

 relation to epidemic diseases, medicine will soon be 

 delivered from empiricism, and placed upon a real 

 scientific basis. When this great day shall come, 

 humanity will recognise that it is to you the greatest 

 part of its gratitude is due.' 



Pasteur approached the study of viruses by seeking 

 to penetrate into all the causes of the terrible malady 

 called splenic fever (charbon, Germ. Milzbrand). Each 

 year this disease decimates the flocks not only in France 

 but in Spain, in Italy, in Eussia, where it is called the 

 Siberian plague, and in Egypt, where it is supposed to 

 date back to the ten plagues of Moses. Hungary and 

 Brazil pay it a formidable yearly tribute ; and to come 

 back to France, the losses have amounted in certain 

 years to from fifteen to twenty millions of francs. 

 For centuries the cause of this pest has eluded all re- 

 .search ; and further, as the malady did not always 



