Chapter 6 : First Recognition: Koch and Cohn

Ferdinand Cohn.

The main building of the University of Breslau (Wroclaw) erected between 1728 and 1732. Photographed in 1987.

Ferdinand Cohn's Institute of Plant Physiology, on the second floor of an old student dormitory, where Robert Koch made his famous demonstrations of the life cycle of anthrax. Cohn himself is sitting in the background.

Ferdinand Cohn's study.

The famous set of drawings of bacterial endospores, illustrating the papers of Cohn and Koch. The original was a color lithograph. Figures 1 through 7 illustrate Koch's paper, the rest refer to Cohn's paper published in the same issue. The legend for Koch's paper follows: Fig. 1. Anthrax bacilli from the blood of a guinea pig. Fig. 2. Anthrax bacilli from the spleen of a mouse, after three hours culture in a drop of aqueous humor. Fig. 3. As Fig. 2, but after 10 hours culture. Fig. 4. As Fig. 2, but after 24 hours. Note the chains of spores. Fig. 5. Spore germination. Fig. 5b was drawn by Cohn to illustrate Koch's paper. Fig. 6. Arrangement for a slide culture. The cover slip has been ringed with olive oil to make it air tight. A warm stage was used to maintain the slide culture near body temperature. Aqueous humor was used for the culture. Even with the naked eye one could see turbidity due to the growth of the long filamentous masses. Fig. 7. Growth of the bacilli in the epithelium of the frog. The bacteria are inside the epithelial cells.