ESSAYS ON BACTERIOLOGY. 161 



Without the proper seed, the most fertile soil under 

 the most favorable conditions produces no com, no 

 wheat. Without the specific germs the body suffers 

 from no typhoid, no diphtheria, no tuberculosis. 



This simple, illuminating analogy between agricul- 

 ture and bacteriology I would leave as the last thought 

 with him who reads these pages. If he will bear it in 

 mind, he will seldom be at loss to understand the 

 germ theory of disease and many of the problems aris- 

 ing out of it. It will make him a better and a clearer 

 thinker about disease. And, being a clearer thinker, 

 he will be a more efficient actor as a physician. 



When once he has seen, what every agriculturist 

 sees, that sunshine and rain and soil and seed must 

 work together to produce the harvest, then he will see 

 how germs may be the direct exciting cause of the in- 

 fectious diseases, into whose production, however, 

 many other factors enter, and often play an important 

 part. And then he will see the beautiful harmony 

 between clinical medicine and bacteriology, one truth 

 only aiding another. 



