INFECTION AND RESISTANCE 



CHAPTER I 



INFECTION AND THE PROBLEM OF VIRULENCE 



THE early history of our knowledge of infectious disease is that 

 of fermentation. It was a philosopher, Robert Boyle, writing in the 

 17th century, who prophesied that the problem of infectious dis- 

 ease would be solved by him who elucidated the nature of fermenta- 

 tion. His prediction was fulfilled 200 years later by the train of 

 investigations begun by Cagniard-Latour and by Schwann, and car- 

 ried to a brilliant culmination by Pasteur. It was the discovery of 

 the living nature of ferments and the specific nature of the various 

 micro-organisms which caused the several forms of fermentation, 

 and especially of putrefaction, which made possible rational investi- 

 gations in the field of infectious disease and led by analogy, first to 

 logical speculation then to actual experimental proof of the etiolog- 

 ical relationship between the minute forms of life and the com- 

 municable diseases. 



It is not much more than 50 years since Pollender described the 

 anthrax bacillus in the blood and spleens of animals dead of this 

 disease. In this short period the large number of maladies of ani- 

 mals and human beings caused by micro-organisms belonging both 

 to the varieties spoken of as bacteria and to those classified as 

 protozoa has necessitated the segregation of this branch of knowl- 

 edge into a separate chapter. 



The period of etiological investigation is now approaching its 

 maturity. The causative agents of most of the more common infec- 

 tious diseases have been discovered, and the biology of many of the 

 pathogenic micro-organisms has been thoroughly studied both in 

 their artificial cultures and in the infected animal body. In spite 

 of a considerable accumulation of facts, however, the science of 

 immunity, that is, the study of the defensive powers of the living 

 animal body against infection, is still in its infancy, and the practi- 

 cal therapeutic successes based on this science are disappointingly out 

 of proportion to the really large amount of detailed knowledge of 

 cellular and serum reactions at our disposal. 



The study of putrefaction and of fermentation though furnish- 

 ing the basic analogy from which the first impulse was obtained 



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