A STUDY 



OF THE 



GERM THEORY OF DISEASE. 



HISTORICAL. 



INTRODUCTION. 



In presenting an historical sketch of the Germ Theory of 

 Disease, it will be my effort to review briefly the ideas, con- 

 troversies and experiments, that have gradually led up to 

 our present knowledge concerning it. At present I know of 

 no single treatise on this subject from which those who have 

 not followed its now extensive literature can gain a clear 

 view of it, obtain a just conception of its magnitude, of the 

 labor that has been bestowed upon it, or of its immense im- 

 portance. The history of this subject in its completeness, 

 would be a history of the efforts of men to stay the ravages 

 of epidemic and contagious diseases ; a history of the efforts 

 of men to understand the causes of plagues and pestilences ; 

 a history of the efforts of men to see farther, and still farther, 

 into the secret causes which produce sickness and diminish 

 the longevity of the race. I cannot, however, give more 

 than a brief synopsis of the principal thought, experiment 

 and discussion, bearing most directly upon, and finally lead- 

 ing to the adoption of present theories. The literature of 

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