176 LOUIS PASTEUE. 



VIRULENT DISEASES. 



SPLENIC FEVER (CHAEBON) SEPTICAEMIA. 



' HE that thoroughly understands the nature of fer- 

 ments and fermentations,' said the physicist Eobert 

 Boyle, ' shall probably be much better able than he 

 that ignores them, to give a fair account of divers 

 phenomena of certain diseases (as well fevers as 

 others), which will perhaps be never properly under- 

 stood without an insight into the doctrine of fermen- 

 tations.' 



At all times, medical theories, more particularly 

 those which concern the etiology of virulent diseases, 

 have had to encounter the opposition of explanations 

 invented to account for the phenomena of fermenta- 

 tion. When Pasteur in 1856 began his labours on 

 these subjects, the ideas of Liebig were everywhere 

 revived. Like the ferments, so the viruses and 

 processes of disease were considered as the results of 

 atomic motions proper to substances in course of 

 molecular change, and able to communicate themselves 

 to the diverse constituents of the living body. 



The researches of Pasteur on the part played by 



