FIRST LECTURE. 



INFECTION AND INTOXICATION. 



SIMON FLEXNER, M.D. 



(ASSOCIATE PROFESSOR OF PATHOLOGY, JOHNS HOPKINS UNIVERSITY.) 



THE science of biology in its widest sense comprises the 

 study of life in all its forms and activities, both normal and 

 abnormal. For this reason I shall not apologize for bringing 

 before you a subject closely related to pathology, a branch 

 which is concerned only with the abnormal forms and activities 

 of life. 



The underlying principles, which are to-day the subjects of 

 thought and research in the branches usually classed as the 

 biological sciences, are not essentially different from those 

 which are also found in the field of work which more pecu- 

 liarly belongs to pathology. Nor is pathology any longer a 

 study, the subject matter of which is limited to man and the 

 higher animals. Its application to the lower animals, and 

 even to plants, has been so successful that we are now 

 justified in looking to the comparative study of disease pro- 

 cesses for the solution of some of the many still obscure prob- 

 lems in human pathology. 



Manifestly it would be neither possible nor profitable to 

 attempt to compass in so brief a time the entire field of path- 

 ological research. It becomes necessary, therefore, to restrict 

 our attention to a single one of its problems ; and as there is at 

 the present time none which is attracting more attention than 

 that relating to the causation and effects of infectious diseases, 

 I have chosen for this hour the discussion of one aspect of this 

 subject. My remarks will be prefaced with a few general 

 statements concerning the parasitic agents of disease. Some 



