INTRODUCTION 31 



in this hitherto but imperfectly cultivated domain. The 

 outcome of these investigations was the establishment of 

 a foundation upon which practical bacteriology of the future 

 was to rest. He, for the first time, demonstrated that dis- 

 tinct varieties of infection, as evidenced by anatomical 

 changes are due in many cases to the activities of specific 

 microorganisms, 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 course of this work that the Abbe system of substange 

 condensing apparatus was first used in bacteriology; that 

 the aniline dyes suggested by Weigert were brought into 

 general use; that the isolation and cultivation of bacteria in 

 pure culture on solid media were shown to be possible; and 

 that animals were employed as a means of obtaining from 

 mixtures pure cultures of pathogenic bacteria. 



With the bounteous harvest of original and important 

 suggestions that was reaped from Koch's classical series 

 of investigations bacteriology reached an epoch in its devel- 

 opment, and at this period practical bacteriology, as we 

 know it today, may justly be said to have had its birth. 



