410 BACTERIOLOGY. 
necrosis of the tissues of the internal organs is of 
comparatively rare occurrence. Caseation of the mes- 
enteric glands, which is commonly observed, is due 
probably to mixed infection. There are, however, a 
number of cases now on record in which the typhoid 
bacillus has played the part of pus producer. Cases 
of sacculated and general peritonitis, subphrenic ab- 
scess, osteomyelitis, periostitis, and inflammatory pro- 
cesses of other kinds have been reported as being 
due to the typhoid bacillus. Kruse also reports an 
abscess of the spleen which contained only bacillus 
typhosus, .and typhoid abscess of the liver has been 
recorded by many. In certain cases of typhoid pneu- 
monia, serous pleurisy, empyema, and meningitis, 
typhoid bacilli exclusively have occurred. The in- 
flammation produced may or may not be accompanied 
by the formation of pus. As argument against the 
observations above cited there has been brought forward 
the supposition that probably the real cause of the 
disease had been destroyed before the entrance of the 
typhoid bacillus. Though this may be true of some 
cases, as in pneumonia, which is caused usually by the 
short-lived pneumococcus, there is no reason to doubt 
the causal relation of the typhoid bacillus to the other 
diseases, inasmuch as it has been proved by numerous 
investigations. 
Such cases, however, are of comparatively rare occur- 
rence, because only exceptionally do the bacilli suffi- 
ciently mass together in such numbers as to become 
pus producers. As a rule, when complications occur 
in typhoid fever they are due to secondary or miwed in- 
fection with the staphylococcus, pneumococcus, strepto- 
coccus, pyocyaneus, and colon bacillus. Frequently 
