SPECIAL BACTERIOLOGY 
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1:20 ; 3rd, 1:40; 4th, 1:80; 5th, 1:160; 6th, 1:320 ; 7th, 
1:640; 8th, 1:1280; 9th, 1:2560; 10th, 1:5120. Make 
similar dilutions in the other three rows, putting 0.2 c.c. 
of immune paratyphoid A serum in the paratyphoid 
A row, 0.2 c.c. of immune paratyphoid B serum in the 
paratyphoid B row, etc. Then take a platinum loop, 
flame it, and having added about 5 c.c. of salt solution 
to the culture tube containing the bacteria you want to 
identify, scrape off the growth, shake well by rotating 
the tube in your hands, and add to every tube in each 
row 5 drops of the bacterial emulsion (to make the en¬ 
tire procedure safe, heat the emulsion for 1 hour at 58° 
C.; this will kill the bacteria but will not interfere with 
the agglutination) ; incubate at 37.5° C. for one hour 
and then examine the tubes; the row which contains 
tubes in highest dilution corresponds to the infection of 
the patient, that is, if the typhoid row (which contains 
tubes with the typhoid immune serum) shows agglutina¬ 
tion in a tube with higher dilution than in any other 
row—your culture is typhoid. 
Since, however, typhoid bacilli may be recovered from 
patient’s blood only during the first ten days of the dis¬ 
ease, and the patient may be brought to the hospital 
later, the blood cultures may prove to be “negative,” 
that is the bacilli will not be found. In such cases, pa¬ 
tient’s blood is removed in a test tube (about 2 to 3 c.c.), 
and Widal test is made. This test is agglutination, but 
just the opposite to that made on the culture: there we 
worked on an unknown culture with known immune 
serums, while now we will work on an unknown serum 
with known cultures: four rows of 10 tubes in each pre¬ 
pared as before, the first tube in each row containing 1.8 
c.c. of salt solution, the others containing 1 c.c. of salt 
solution; the rows again are labeled as before ‘ ‘ typhoid, 
‘ ‘ paratyphoid A, ” “ paratyphoid B, ’ ’ and ‘ ‘ colon. ’ ’ Now 
