INTRODUCTION. 29 
Neisser, in the same year (1879), discovered the 
“¢ gonococcus’’ in gonorrheeal discharges. 
In 1880, Eberth and Koch independently observed 
the typhoid bacillus, but it was not until 1884 that 
Gaffky published his important researches, and proved 
the etiological relation of this bacillus to typhoid fever. 
In the same year (1880) several important communi- 
cations in bacteriological research appeared. Pasteur 
published his discovery of the bacillus of fowl cholera 
and his investigations upon the attenuation of the virus 
of anthrax and of fowl cholera, and upon protective 
inoculation against these diseases. 
Sternberg and Pasteur independently observed (1880) 
a pathogenic micrococcus in saliva, which was subse- 
quently proved by Fraenkel and others (1885) to be 
the organism most commonly associated with acute 
croupous pneumonia—the ‘‘ diplococcus pneumoniz’’— 
and now recognized as the usual cause of that disease. 
In 1881, Koch made his fundamental researches upon 
pathogenic bacteria, the result of which was the estab- 
lishment of a foundation upon which bacteriology of the 
future was to rest. He introduced solid culture media 
and the ‘‘ plate method”? for obtaining pure cultures, 
and showed how different organisms could be isolated, 
cultivated independently, and by inoculation of pure 
cultures into susceptible animals made, in many cases, 
to reproduce the specific disease of which they were the 
cause ; and he laid down the laws by which it may be 
proved that a micro-organism is the specific cause of 
a disease. It was in the course of this work that the 
Abbe system of substage condensing apparatus was first 
used in bacteriology and that Weigert’s method of 
staining was generally employed. 
