TYPHOID FEVER 85 



Process. Prepare an emulsion as described under the 

 microscopic method, but making it decidedly thick, so that it 

 appears markedly opalescent in the narrow glass pipette 

 described above; about 5 c.c. of tap-water (not distilled) will 

 be required for a well-grown twenty-four-hours agar culture. 

 It is not necessary to filter it. Or an emulsion of dead bacilli 

 may be used. 



Fit an indiarubber nipple to the pipette marked i, compress 

 it, dip the tip into the emulsion, and relax the pressure until 

 the column reaches to the unit mark. Remove the tip from 

 the fluid and relax the pressure again, sucking up a short 

 column of air. Reinsert the pipette, and suck up another 

 unit, which will be separated from the first by the bubble of 

 air. Repeat the process until you have sucked up nine units 

 of emulsion separated by eight bubbles of air. Blow them 

 all out into a watch-glass. 



In the same way take two units of emulsion and put them 

 into the second watch-glass, and four units and put them in 

 the third, using the same pipette. 



Now take one unit of serum (avoiding corpuscles) and mix 

 it with the nine units of emulsion in the first watch-glass. 

 This will give a dilution of i in 10. Quickly take one unit of 

 this and mix it with the two units in the second watch-glass, 

 and again take one unit from the first mixture and mix it 

 with the four units in the third watch-glass. This will give 

 you three mixtures of i in 10, i in 30, and i in 50 respectively. 



Suck up part or the whole of the i in 10 dilution into the 

 pipette marked i, then suck up a little air and seal the tip of 

 the pipette in the flame. When it is cool it is advisable to 

 stand it in a test-tube of i in 20 carbolic for safety. 



Take up the i in 30 in the pipette marked 2, draw the 

 column of fluid from the tip, as before, and seal the end. 



Take up the i in 50 in the pipette marked 3 and seal. 



Lastly, suck up a column of the typhoid emulsion unmixed 

 with serum into the fourth pipette, and seal it. This is to act 

 as a control, to make sure that the emulsion does not clump 

 and settle spontaneously. This false clumping is, in the con- 

 ditions of the test as here described, much less common than 

 when the microscopic method is used. 



The tubes must now be incubated at the body temperature. 

 The simplest plan is to heat a large test-tube of water (or 



