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TYPHOID FEVER.                        369

vigorous saprophytes outgrow them and cause their dis-
appearance in a few days. When buried in the upper
layers of the soil the bacilli retain their vitality for nearly
six months. Robertsonl found that when planted in
soil and occasionally fed by pouring bouillon upon the
surface, the typhoid bacillus maintained its vitality for
twelve months. He suggests that it may do the same
in connection with leaky drains.

Cold has no effect upon typhoid bacilli, for freezing
and thawing several times are without injury to them.
They have been found to remain alive upon linen for
from sixty to seventy-two days, and upon buckskin for
from eighty to eighty-five days. Sternberg has succeeded
in keeping hermetically sealed bouillon cultures alive for
more than a year. In the experience of the author, un-
less transplanted rather frequently, cultures upon agar-
agar are apt to die out. In the presence of chemical
agents the bacillus is also able to retain its vitality, o. i
to 6.2 per cent, of carbolic acid added to the culture-
media being without effect upon its growth. At one
time the tolerance to carbolic acid was thought to be
characteristic, but it is now known to be shared by other
bacteria. The bacilli seem to be killed in a short time
by thorough drying.

The bacillus is best secured in pure culture, either
from an enlarged lymphatic gland or from the splenic
pulp of a case of typhoid. To secure the bacillus in this
way the autopsy should be made as soon after death as
possible, lest the Bacillus coli invade the tissue.

Cultures of the typhoid bacillus may be obtained, but
with difficulty, from the alvine discharges of typhoid,
patients. In examining this material, however, it must,
be remembered that the bacilli are certain to be present
only in the second and third weeks.

As numerous saprophytic bacteria are present in the
feces, the resistance which the typhoid bacillus exhibits
to carbolic acid can be made use of in obtaining the pure

1 Brit. Med. Jour., Jan. 8, 1898.