Robert Koch. X1xX 
grow outside the body as well as inside. He succeeded in cultivating many 
successive generations of them in broth, and also watched their growth upon 
a hot stage. He discovered that they formed spores when grown outside the 
body or when blood containing them was allowed to dry; determined the 
greatly increased resistance of the spores to physical and chemical agents ; 
and showed that as long, and only as long, as the broth or dried material 
contained bacilli or spores capable of propagating themselves, these remained 
infective for animals. 
The importance of the anthrax ee can hardly be over-estimated. It 
afforded for the first time convincing proof of the causal relation of a 
particular bacillus to a particular disease. Owing to the unmistakable 
character of the bacillus, and its presence in large numbers in the blood of 
infected animals, its study could be profitably undertaken with the means 
available. 
Koch was unremitting in his efforts to improve his microscopical technique, 
and in the same year published a paper on the investigation, preservation, 
and photographing of bacteria, in which an account of the preparation and 
staining of dry films is given. The method described is very much that still 
in daily use. The paper is accompanied by photomicrographs of bacteria, 
the excellence of which is rarely equalled at the present day. Koch pointed 
out that he had persevered in this work because he was obsessed with the 
idea that the hitherto conflicting results of investigations on the causation of 
infective diseases had their foundation in the incompleteness of the methods 
used. 
Koch’s interest in traumatic infectious diseases seems to have been 
stimulated by the disasters due to these causes amongst the wounded in 
the Franco-Prussian war. The results of Lister’s antiseptic methods had 
demonstrated that means directed against the infection of wounds with 
microbes obviated these diseases. Micrococci and bacteria had frequently 
been found in pus, diphtheritic ulceration, in the tissues at the edge of 
advancing erysipelas, and in pyemic deposits. Micro-organisms had also 
been discovered in the blood in relapsing. fever and puerperal fever. 
- Further, Coze and Feltz and Davaine had inoculated rabbits with the blood 
of patients dead of puerperal fever, and had succeeded in carrying on the 
infection through successive generations of these animals. Nevertheless, the 
evidence that a particular organism was the cause of a particular disease was 
far from conclusive. Many observers concluded that bacteria were universally 
present in the normal body. Others failed to find any organisms in obviously 
septic conditions. There was no practicable means of separating one coccus 
from another coccus, and bacteria of identical appearance were found to be 
associated with a variety of diseases. The parasitic nature of traumatic 
diseases was probable, but unproven. 
Koch began his work on traumatic infective diseases with the conviction 
that the most fruitful line of investigation would be a comparative one, 
namely, to induce septic infections in animals and see whether they would 
