BACILLI OF THE COLON. 
69 
The Bacillus Paratyphosus. 
The paratyphoid bacillus in shape and size is very 
much like the typhoid bacillus. It is differentiated 
from the typhoid bacillus by its ability to ferment glu¬ 
cose. There are two types of paratyphoid bacilli, 
called type A and B, which differ slightly in their 
method of growth. They also behave differently in the 
agglutination or Widal reaction. The blood of the 
patients sick with paratyphoid fever will not agglu¬ 
tinate the typhoid bacillus. If the infection is due to 
paratyphoid A the blood will not agglutinate the para¬ 
typhoid B, but only the A. 
The agglutination reaction is a very good way to 
diagnose the type of infection present in all cases of 
typhoid-like infection. 
The course of the fever in paratyphoid infections 
is somewhat milder and shorter than in typhoid. In 
the fatal cases coming to autopsy the spleen and mesen¬ 
teric glands are enlarged, just as in typhoid, but 
the intestines show little change. Changes in the 
bowel do occur because hemorrhage sometimes occurs 
in paratyphoid fever. 
Immunity follows an attack of paratyphoid fever 
just as in true typhoid, but the protection is only 
against the type of paratyphoid bacillus causing the 
infection. A case illustrating this point came under 
the writer’s observation in the summer of 1913, in 
which the patient developed typhoid-like symptoms 
and fever, although he had had a severe typhoid in- 
