TYPHOID FEVER 77 



Macroscopic Method. 

 The macroscopic method can be carried out with a young living 

 culture on agar, or with an emulsion of dead bacilli. The technique 

 is not difficult, and no apparatus is required other than a piece of 

 narrow glass tubing, from which to make pipettes. 



Requisites.— I. A young culture on agar, and some normal 

 saline solution ; or a dead emulsion of typhoid bacilli. 



2. Special glass pipettes. These are in every respect like the 

 opsonin pipette (see Fig. 33), and are readily extemporized from 

 a piece of glass tubing. Four such pipettes are required if the 

 blood is to be tested in dilutions of i in 10, i in 30, and i in 50, 

 which are the most convenient amounts in practice. First 

 number them i, 2, 3, and 4 with a grease pencil, and make a 

 transverse mark about an inch from the tip (or less if you have 

 only a small amount of serum) on that labelled i. This tip should 

 be a good one, as described for an opsonin pipette. This is less 

 important for the others, which are not used for measuring units. 

 Three small watch-glasses, or a glass slide, or a porcelain slab 

 with concavities ground into it, should be at hand for making the 

 dilutions. 



Process. — Prepare an emulsion as before, 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 fiher 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 



