CHAPTER V 
DISEASES CAUSED BY BACTERIA 
GENUS BACILLUS 
General discussion of the genus bacillus. The genus Bacillus in 
Migula’s classification includes all rod-shaped motile bacteria. In 
the older classifications it includes both non-motile and motile forms. 
The fixing upon motility as an essential generic character, and thus 
restricting the genus Bacillus to motile forms, is the occasion of some 
confusion between the genera Bacterium and Bacillus as applied to a 
number of important disease-producing bacteria. It is customary to 
speak of the Bacillus of anthrax, of tuberculosis and of glanders 
rather than of the Bacterium of these affections. There are a number 
of species of bacilli that are widely separated from each other. The 
diseases which they produce give very different pictures both clini- 
cally and in their morbid anatomy. 
There are a few species that are especially important from the 
rather non-specific nature of the infections they produce. The colon 
bacilli, including the bacilli belonging to the intermediate or Geertner 
group, furnish good illustrations of this. They are found in a great 
variety of lesions but they do not seem to produce a constant, clearly: 
defined reaction on the part of the infected tissues. There are other 
species that are significant because of the constant character of the 
lesions they produce regardless of the location in the body or the 
species of animals attacked. This is particularly true of the bacillus 
of necrosis. These two groups of bacilli (colon and necrophorus) are, 
for domesticated animals, the most important etiologically outside of 
those that produce specific infectious diseases such as tetanus and 
symptomatic anthrax. 
SALMONELLOSIS 
Characterization. The term Salmonellosis has been introduced to 
designate the disease caused by Bacillus suipestifer (Bacillus cholerae 
suis) described in 1885 by Salmon and Smith. It is usually, if not 
always, possessed of a low degree of virulence for swine. It was 
believed at the time to be the cause of hog cholera. The discovery of 
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