AGf~ICULTURAL RESEARCH, PUSA.

41110 PRACTICAL BACTERIOLOGY
The "Sigma" and the "Kahn" reactions are
flocculation tests in which the technique of the original
reaction of Saehs and Geol'gi has heen modified.
The Mcinieke reaction is somewhat similar, and is
descrihed Oil p. 222.
DIAGNOSIS
In the primary stage, when there is an ulcerated
sore, T'I'. palliduln cnn l1slIally he demonstrated in
the serous exudate from the ulcer. The dark-ground
illurnination method is the ideal technique for the
purpose, and provides a cOllvenient means of l'apid
diagnosis. Failing this, Fontana's staining method
can he used.
'1'1'. pallidum is recognised hy its special morphological
features, and must be carefully differentiated
from othel' spirochaetes found in ulcerating sorcsc.g.
1'1'. gracile, etc. (vide inF(t).
D1'rections for obtaining a specimen of exudate .from a
syphilitic SM'e for microscopic examination:
The serous exudate should he obtninecl from the
tissue, and should not include surface organisms,
as other spirochaetes which may be confused
with the 1'1'. palUdwn are frequently present.
Thc prcsence of excessive numbers of red blood
corpuscles in the specimen is also to be avoided,
as they tend to obscure the spirochaetes. If a
local antiseptic has been used it may not be
possible to find spirochaetes until a "\vet dressing
of gauze soaked in sterile saline solution has been
applied to the sore for twenty-four to forty-eight
hours. It is to be noted also that antisyphilitic
treatment, initiated before the examination,
diminishes the likelihood of successful microscopic
diagnosis.
The sore is cleansed with a swab soaked in warm
saline solution, and the margin is then scraped
lightly with some hlunt instrument to abrade the
supCl'Hcial epithelium.. On squeezing the hase of