WIDAL'S METHOD. 87 



avoid air-bubbles. This is because the test is easier to 

 carry out and is more conclusive if clear serum can be 

 obtained. The test may be applied to a dry drop of 

 blood, but in this case there is no possibility of making 

 an accurate dilution. The test is wonderful enough as 

 it is, but the practitioner should not expect too much 

 from it if he sends a few splashes of blood inside a 

 capillary tube of the pipette. This is so important that 

 we repeat : do not be satisfied unless the bulb is com- 

 pletely filled with blood. When this is accomplished 

 suck the fluid a little further up and seal the pointed 

 end of the pipette in a flame the flame of a wax match 

 will answer. 



If a pipette is not at hand it is advisable to manufac- 

 ture one out of any piece of glass tubing which may be 

 available. Failing this the best plan is to dry several 

 large drops of blood on a clean slide ; but results ob- 

 tained from blood forwarded to a laboratory in this way 

 should be received with caution, for the dilution is 

 necessarily a matter of guess-work. 



Do not send blood in vaccine tubes. When this is 

 done the blood often adheres so firmly to the glass that 

 the whole tube has to be ground down in a mortar with 

 a drop or two of water. 



METHOD OF PERFORMING WIDAL'S REACTION BY THE 

 MICROSCOPIC METHOD. 



Requisites. i. A young culture (not more than eigh- 

 teen hours old) of typhoid bacilli on agar. 



Where dead bacilli are to be used this is to be re- 

 placed by a culture obtained from the laboratory and 

 prepared in the manner described. 



