TYPHOID , FEVER 8; 



METHOD OF PERFORMING WIDAL'S REACTION BY THE 

 MICROSCOPIC METHOD. 



Requisites. i. A young culture (not more than eighteen 

 hours old) of typhoid bacilli on agar. 



2. A small funnel provided with a double thickness of white 

 filter-paper. This is unnecessary if dead cultures are to be 

 used. 



3. Three clean watch-glasses. 



4. A platinum loop. This should be made of fine wire and 

 have a loop (which must be completely closed) about TG inch 

 in diameter. 



5. A hollow-ground slide. This is an ordinary slide having 

 a well about \ inch in diameter sunk in its centre. If it is 

 not at hand a cell may be built up on an ordinary slide. Take 

 a piece of thin card i inch square and cut out a square J inch 

 in diameter from its centre. Fix this perforated square down 

 on to the slide with vaseline or immersion oil. 



6. Thin cover-glasses. 



7. The microscope. The test can be carried out quite well 

 with a J-inch lens. 



Process i. Making the Emulsion. Pour a small quantity 

 of tap-water into the culture-tube, or, better, scape off some 

 of the growth and mix it with some water in a watch-glass. 

 In either case stir it round with the platinum needle for a few 

 minutes, so that the bacilli are evenly distributed throughout 

 the water and form an emulsion. 



Next take the hollow-ground slide and paint a ring of 

 immersion oil round the well (Fig. 19, b). If you are using a 

 built-up cell, paint the top of the card with the oil. In either 

 case vaseline- may be used. 



Place a drop of the emulsion on a clean dry cover-glass, 

 and invert the hollow-ground slide over it; press it down so 

 that the oil round the well adheres to the cover-glass; now 

 invert the slide, and you will have a hanging-drop specimen. 

 The bacilli will be contained in the droplet of water (Fig. 19, a) 

 which hangs from the lower surface of the cover-glass : this 

 will not dry up if the seal made by the oil is perfect. 



Place the specimen under the microscope and examine it 

 with the low power, using the fine adjustment and stopping- 

 down the diaphragm. Focus until the surface of the cover- 



