WIDAL SERUM TEST 8 1 



motility of the bacilli and their aggregation into clumps. 

 Specify the time elapsing before the agglutination appears and 

 the time required for the complete clumping. 



Make a similar examination of a culture to which i/io blood 

 serum has been added. 



Repeat the above test with the blood from animals affected 

 with or immunized against hog cholera. 



Examine a dried specimen of blood for this reaction. Add 

 a drop of bouillon to the drop of dried blood on a slide, and 

 after it has become well mixed add a loopful of it to a similar 

 quantity of a fresh bouillon culture and examine it immediately 

 in a hanging drop. 



127. Securing Blood for the "Widal Test. — (i) Dried prep- 

 arations. Prick the finger or lobe of the ear (if a lower animal 

 the shaved ear is a good place) sufficiently deep to procure a 

 drop of blood. Place it on a slide by means of a platinum loop 

 and allow it to dry. (2) Serum. From a similar but deeper 

 prick, or by drawing a few drops of blood from a vein with a 

 hypodermic syringe, secure a few drops of blood. Place them 

 in the bottom of a small, short, sterile tube and allow the serum 

 to ooze out. This can often be helped by separating the blood 

 from the tube by means of a sterile wire. If retained for any 

 length of time before making the test, the serum must be kept 

 in a cool place. Experimentally, it is easily obtained by im- 

 munizing a guinea pig and then drawing the desired amount of 

 blood from a vein. 



