10 HISTORICAL OUTLINE 



practising physician at Wollstein, attacked the problem of anthrax, and pro- 

 duced, as his first contribution to science, a demonstration of the character and 

 mode of growth of the causative bacillus, which opened a new era in bacterio- 

 logical technique. This memoir he published in 1876. In the following year he 

 published his methods of preparing, fixing, and staining film-preparations of bacteria, 

 using the aniline dyes introduced into histology by Weigert, and described his 

 methods of photographing such preparations. In 1878 he published his memoir 

 on traumatic infective diseases, which remains a classical example of the study of 

 experimental infections in laboratory animals. In 1881 he described his method 

 of preparing cultures on solid media, a technical advance of the first importance, 

 since it made possible the isolation of pure strains of bacteria from single colonies. 

 Solid media prepared from naturally occurring material such as pieces of potato, had 

 previously been used for the isolation of micro-organisms, particularly by mycolo- 

 gists, and the general principles to be observed in the preparation of pure cultures had 

 been clearly enunciated by Brefeld, who had suggested the solidification of a nutrient 

 medium by the addition of gelatin. The media and methods available for the culti- 

 vation of fungi were not, however, well suited for bacteria ; and it was left for Koch 

 to devise, in the form of his nutrient gelatin, and later, at the suggestion of Frau 

 Hesse, of nutrient agar, a solid, transparent medium, easy to sterilize and handle, and 

 thus admirably adapted for obtaining isolated colonies of bacteria (see Bulloch 1930). 

 In 1882 and 1884 he published his classical papers on the bacillus of tuberculosis. 

 In 1883 he discovered the vibrio of cholera. Already, Koch had enlisted the 

 services of Loefiler and of Gaffky as his assistants. Later came Pfeifier, Kitasato, 

 Welch and many others, and, with his growing fame, he began to gather round him 

 a group of keen and able young men, who were destined to introduce the methods 

 he devised into the laboratories of many lands. In 1885 he was appointed Professor 

 of Hygiene and Bacteriology in Berlin, and in 1891 he was made Director of the 

 newly-founded Institute for Infective Diseases. His later years were devoted almost 

 entirely to the investigation of bacteriological problems in their relation to the 

 prevention and cure of disease, and many of his contributions to our knowledge 

 will be considered in later chapters. Koch was, above all, an able and careful 

 technician. He was greatly aided by the vigour and initiative of the great German 

 chemical and optical firms, and the advances which he made in staining methods, 

 in the use of the microscope for the observation of bacteriological preparations, 

 and in the technique of cultivating bacteria, revolutionized this branch of 

 science. 



The fruits of this revolution appeared with surprising rapidity. During the 

 last quarter of the nineteenth century a succession of discoveries was reported, 

 bearing on the relation of bacteria to human and animal disease, which opened a 

 new era in medicine. 



In 1874 Hansen desco-ibed the bacillus of leprosy, and Neisser, in 1879, the gono- 

 coccus. In 1880 Pasteur recorded the isolation of the bacillus of fowl cholera, and 

 Eberth observed the bacillus of typhoid fever. In 1881 Ogston published an adequate 

 description of the staphylococcus. In 1882 Koch discovered the tubercle bacillus, 

 and Loefiler and Schiitz the bacillus of glanders. In 1883 Koch discovered the 

 cholera vibrio, Fehleisen isolated the streptococcus of erysipelas, and Klebs 

 described, but did not isolate, the bacillus of diphtheria. In 1884 Loefiler isolated, 

 and subjected to thorough study, the bacillus which Klebs had briefly described 

 in the previous year, and GafEky isolated and studied the typhoid bacillus, which 



