12 BACTERIOLOGY 



knew not how nor when. He learned that those who 

 were seized upon by this foe were a source of danger 

 to others, as were likewise their clothing and their 

 houses. In other words, he learned that diseases were 

 contagious, but how or why he knew not. 



For ages the leper had been considered " unclean/' 

 and since the dawn of the world of man had plague- 

 infested cities been shunned, and, later, those who were 

 afflicted and their habitations were purified by baths 

 and smudges and noxious fumes. 



Then an observing Dutchman of an inventive turn, 

 Leeuwenhoek, of Delft, about the year 1680 produced 

 a lens of such power that this enemy of man could be 

 seen, though it was not recognized as such at that time. 

 Though Leeuwenhoek certainly discovered the existence 

 of bacteria and described them, neither he nor any one 

 else succeeded in connecting them with disease for nearly 

 two centuries. So for two hundred years, though its 

 presence was known and its guilt ofttimes suspected, 

 the disease germ remained unconvicted. 



Oliver Wendell Holmes, an American physician- 

 author, in 1843 suspected the cause of puerperal fever 

 and wrote on its contagiousness. In reply to the 

 criticism and invectives which were heaped upon him 

 because he ventured so new and astonishing an idea in 

 medicine he wrote: 



" It is as a lesson rather than a reproach that I call 

 up the memory of these irreparable errors and wrongs; 



