INTRODUCTION 21 
shown to be the etiological factor of a bacterial disease. Koch also 
found that the anthrax bacillus formed spores. 
From this time bacteriology developed with amazing rapidity. On 
March 24, 18S2, Koch reported the cultivation of the tubercle bacillus 
to the Physiological Society in Berlin. This remarkable work was soon 
published/ and startled the world. Almost at once, and in rapid suc- 
cession, typhoid, diphtheria, cholera, tetanus and other well-known 
pathogenic bacteria were isolated and studied in pure culture. 
In 1882 Metchnikoff published the first of his highly important 
contributions to immunity and phagocytosis, and a decade later von 
Behring and Kitasato announced the discovery of diphtheria antitoxin. 
This was followed by the careful studies upon the humoral aspects 
of immunity by Ehrlich and his collaborators, beginning in 1897, and 
continued for several years, during which time the standardization 
of diphtheria and tetanus toxin and antitoxin was placed upon a 
definite basis. 
The last three decades have not only witnessed the rise and develop- 
ment of these most brilliant chapters of medicine, infection and immu- 
nity; but sanitation, agriculture, many industries and other fields 
of human activity have benefited largely by the deA'elopment of 
bacteriology. 
In medicine the diagnosis of bacterial disease has reached a high 
degree of precision, and bacteriological diagnosis is an important branch 
of medical science. The most important problem for the future is to 
create a system of Bacterial Therapeutics of equal efficiency. 
1 Berl. klin. Wchnschr., 1882, 19, 221. 
