654 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1911. 



The publication of these three papers raised the hitherto obscure 

 physician of Wollstein to the first rank of scientific investigators, but 

 they were merely the beginning of his scientific career. Their 

 importance and the genius of their author was recognized by Struck, 

 the enlightened director of the German health office, who invited 

 Koch to accept a position in that department. The chemical and 

 hygiene laboratories attached to the department had been exten- 

 sively equipped, but bacteriology was naturally unprovided for. A 

 room was, however, found for him, and in these humble surroundings 

 he settled down to pursue his inquiries. He was soon joined by 

 Loeffler and Gaffky, who became his first assistants. The three 

 worked together enthusiastically in the one room, fitting up the 

 laboratory, inventing apparatus, and improving fnethods. The 

 great problem confronting them was to find a practicable means of 

 obtaining a pure culture outside the body. Koch accomplished this 

 by the simple expedient of adding gelatin to the nutrient medium. 

 The gelatin-containing medium was inoculated whilst warm with a 

 minute amount of the material, poured in a thin layer upon a plate 

 and allowed to set. In this way bacterial colonies originating from 

 individual microbes were obtained. Portions from the colonies were 

 subsequently sown into separate tubes of broth or other fluid suitable 

 for their growth. The discovery of this technique made advance 

 possible. 



Another line of investigation undertaken at this time, on account 

 of its importance in the technique of bacteriology, was concerned with 

 disinfection and sterilization. The experiments of Koch and his 

 pupils, made upon pure cultures of pathogenic bacteria, is the foun- 

 dation upon which all later work on this subject has been built. It 

 also led to the substitution of the more convenient steam steriliza- 

 tion for dry heat. 



One can not emphasize too strongly to what a large extent Koch 

 provided the tools of inquiry at each stage in the development of 

 bacteriology, but he did not rest there. From 1880 onward followed 

 a period of extraordinary activity. In a dozen years the etiological 

 factor of 11 important human diseases — tubercle, cholera, typhoid, 

 diphtheria, erysipelas, tetanus, glanders, pneumonia, epidemic menin- 

 gitis, influenza, and plague, as well as numerous animal diseases — 

 was discovered by Koch and his pupils. 



After the completion of his work on anthrax Koch's individual 

 efforts were directed more particularly to the discovery of the infec- 

 tive agent in tuberculosis, whilst diphtheria and typhoid were being 

 investigated by his assistants, Loeffler and Gaffky. The work of 

 Klencke and Villemin and the further experiments of Cohnheim and 

 Salomonsen, had established that the disease tuberculosis was due to 

 an infective agent which was capable of propagating itself in the animal 



