BACILLUS TYPHOSUS. 413 
Not only do the very great majority of cases exam- 
ined bacteriologically and pathologically, but the epi- 
demiological history of the disease, prove that the 
chief mode of invasion of the typhoid bacillus is by 
way of the mouth and stomach. The infective mate- 
rial is discharged principally by means of the excretions 
and secretions of the sick—namely, by the feces, the 
urine, and occasionally by the sputum. 
Of considerable practical importance is it to know for 
what length of time the typhoid bacillus is capable of 
living outside of the body; but, unfortunately, owing 
to the great difficulties in proving the presence of this 
organism in natural conditions, our knowledge on this 
point is very deficient. In feces the length of life of 
the typhoid bacilli is very variable; sometimes they 
live but a few hours, usually a few days, exceptionally 
for very long periods. Thus, according to Uffelmann, 
typhoid bacilli may remain alive in feces for five and 
a half months, and, according to Karlinski, for at least 
several months. Foote says that they can be found in 
living oysters for a month at a time. Their life in 
feces and in water, however, is usually very much 
shorter. As a rule, they can be detected in water no 
longer than fourteen days after introduction. The 
life of the typhoid bacillus varies according to the 
abundance and varieties of the bacteria associated with 
it and according to the presence or absence of such in- 
jurious influences as high temperature, light, desicca- 
tion, etc., to which it is peculiarly sensitive. That the 
bacilli do live much longer under favorable circum- 
stances, as to protection and nourishment, than is gen- 
erally supposed, is shown by the fact, as reported by 
Buschke, that they were found in an old bone-centre 
