BACILLI OF THE COLON. 
71 
other epidemics in this country we find that there are 
a number of bacilli very nearly alike that may cause 
these epidemics of dysentery. 
Individuals that have been infected with dysen¬ 
tery bacilli develop agglutinating substances in the 
blood that will clump the dysentery bacilli just as in 
the case of typhoid and paratyphoid infections. 
To summarize what has been said of the colon- 
typhoid-dysentery group: All the members are bacilli 
of similar appearance, all are to some degree motile, 
but they differ one from another in their growth, par¬ 
ticularly in their ability to ferment sugars and pro¬ 
duce acid in culture media. The colon group, although 
a constant inhabitant of the intestine, gives rise to no 
infection unless it gains access to tissues outside the 
bowel. The typhoid and dysentery bacilli are never 
present in the body under normal conditions, but when 
they enter the body they cause a characteristic infec¬ 
tion. The blood-serum of all infected individuals 
develops substances that protect against reinfection, 
and among these substances are the agglutinins which 
gather the bacilli together into clumps. The agglu¬ 
tinins caused by infection with the colon bacillus will 
agglutinate only the colon bacillus; the same is true 
for the typhoid, paratyphoid, and dysentery bacilli. 
This peculiarity is made use of in diagnosing the kind 
of infection present. 
The Mucosus Capsulatus Group. 
In this group are placed a number of micro¬ 
organisms which resemble one another closely in their 
