INTRODUCTION 



L'homme en ce siecle a pris une connaissance toute nouvelle des ressource des 

 la nature et, par 1'application de son intelligence il a commence a les faire 

 fructifier. II a refait, par la geologie et la paleontologie, 1'histoire de la terre, 

 entrained elle-meme par la grande loi de 1'evolution. II connait mieux, grace a 

 Pasteur surtout, les conditions d'existence de son propre organisme et peut entre- 

 prendre d'y combattre les causes de destruction. Monod, L' 'Europe Con- 

 temporaine. 



WHETHER to admire more the man or his method, the life or 

 the work, I leave for the readers of this well-told story to 

 decide. Among the researches that have made the name of 

 Pasteur a household word in the civilised world, three are of 

 the first importance a knowledge of the true nature of the 

 processes in fermentation a knowledge of the chief maladies 

 which have scourged man and animals a knowledge of the 

 measures by which either the body may be protected against 

 these diseases, or the poison neutralised when once within the 

 body. 



I. 



Our knowledge of disease has advanced in a curiously 

 uniform way. The objective features, the symptoms, natur- 

 ally first attracted attention. The Greek physicians, Hippoc- 

 rates, Galen, and Aretaeus, gave excellent accounts of many 

 diseases ; for example, the forms of malaria. They knew, too, 

 very well, their modes of termination, and the art of prognosis 

 was studied carefully. But of the actual causes of disease they 

 knew little or nothing, and any glimmerings of truth were 

 obscured in a cloud of theory. The treatment was haphazard, 

 partly the outcome of experience, partly based upon false 

 theories of the cause of the disease. This may be said to have 

 been the sort of knowledge possessed by the profession until 



