60 
BACTERIOLOGY. 
tured appendix. Occasionally it causes a general in¬ 
fection. The poisons of the colon bacillus are con¬ 
tained within the body of the organism and are 
liberated only when it disintegrates. The knowledge 
of this fact has made it possible to immunize against 
colon infections by injecting the dead cultures, or 
vaccine, in slowly increasing doses. (See Immunity.) 
On account of its constant presence in the intes¬ 
tine of man and animals, the presence of the colon 
bacillus in water or milk leads to the assumption that 
they have become infected with intestinal discharges, 
and so not safe for consumption. On account of the 
wide distribution of . the colon bacillus in nature, this 
view has been modified to some extent, and now, 
unless they are present in excessive number, the water 
or milk is not condemned. 
The Bacillus Typhosus. 
The typhoid bacillus is the cause of typhoid fever. 
In recent years we have come to recognize that there 
are a number of other micro-organisms closely related 
to the typhoid bacillus which produce a fever and other 
symptoms that make a clinical picture identical with 
typhoid fever. It is more accurate therefore to look 
upon the clinical condition of typhoid as being due to 
any one of a group of micro-organisms the chief 
members of which are the typhoid, paratyphoid, and 
paracolon bacilli, with forms intermediate between 
each. 
