84 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



from the patient suspected to be suffering from the disease to 

 a larger amount of a young culture of typhoid bacilli, and 

 watching whether the appearance of the culture undergoes 

 any change : it may be watched under the microscope or by 

 the naked eye, the technique differing in the two cases. The 

 macroscopic method is in every way the more satisfactory, 

 if the method used, or any simple modification thereof, be 

 followed. It is a good plan for the student to familiarize 

 himself with the appearances seen in the microscopic method, 

 and for that reason it will be described here. But in practice 

 the convenient, easy, and accurate pipette method has almost 

 entirely replaced it. 



Collect the blood from the ear, as described on p. 35, taking 

 care to get a Wright's pipette about half full. The test may 

 be applied to a dry drop of blood, but in this case there is no 

 possibility of making an accurate dilution, and unless a fair 

 quantity of serum is at hand it is impossible to perform the 

 test by the macroscopic method. 



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. 35), 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. 



