INTRODUCTION 29 



the access of organisms from without that decomposition 

 primarily originated. (See page 22.) 



Under careful precautions, to which no objection could 

 be raised, the experiments of Billroth and Tiegel were 

 repeated by Pasteur, Burdon-Sanderson, and Klebs, but 

 with failure in every instance to demonstrate the presence 

 of bacteria in the healthy living tissues. 



The fundamental researches of Koch (1881) upon patho- 

 genic bacteria and their relation to the infectious diseases 

 of animals differed from those of preceding investigators 

 in many important respects. The scientific methods of 

 analysis with which each and every obscure problem was 

 met as it arose served at once to distinguish him as a pioneer 

 in this hitherto but imperfectly cultivated domain. The 

 outcome of these investigations was the establishment of 

 a foundation upon which bacteriology of the future was to 

 rest. He, for the first time, demonstrated that distinct 

 varieties of infection, as evidenced by anatomical changes, 

 are due in many cases to the activities of specific micro- 

 organisms, and that by proper methods it is possible to 

 isolate these organisms in pure culture, to cultivate them 

 indefinitely under artificial conditions, to reproduce the 

 lesions by inoculation of these pure cultures into susceptible 

 animals, and to continue the disease at will by continuous 

 inoculation from an infected to a healthy animal. By the 

 methods that he employed he demonstrated a series of 

 separate and distinct diseases that can be produced in mice 

 and rabbits by the injection of putrid substances into their 

 tissues. The disease known as septicemia of mice; likewise 

 a disease characterized by progressive abscess-formation, 

 and pyemia and septicemia of rabbits, were among the 

 affections first produced by him in this way. It was in the 



