1881

Koch publishes paper introducing his “plate technique” (pure culture technique using solid or semi-solid media) and its use in studying pathogenic organisms), the “Bible of Bacteriology.” He used nutrient gelatin to make solid the liquids (e.g., nutrient broths and bouillons) that supported the growth of pathogens. In 1882, gelatin replaced by agar, via his student Walther Hesse (Brock, 94-104). Koch begins experiments leading to discovery of tubercle bacillus in 1882, which involved (a) discovery of technique for staining tubercle bacillus; (b) demonstration that bacillus is invariably present when TB is present; and (c) demonstration that pure cultures of tubercle bacillus are virulent and invariably cause TB when experimental animals (guinea pigs) were incubated with it (Brock, 117ff.; Daniel, 78-82; Caldwell, 159-162)