73 
7. With a sterile 1 cc. pipette measure 1 cc. of the bacterial suspension 
(antigen) into each of eight small test tubes. Arrange the tubes in two rows 
in the rack. Number the tubes from left to right in the two rows as follows: 
Front row: Al, A2, A3, and A4; backrow: Bl, B2, B3, and B4. Place the im¬ 
mune serum in the front row of tubes. 
FIG. 21—DIAGRAM FOR SERUM DILUTIONS 
The dilutions are made with the 0.1 cc. pipette. The proceedure shown for the immune serum is 
the same for the normal serum. 
8. Use a sterile 0.1 cc. pipette, and prepare the following dilutions of each 
of the sera; rinsing the pipette in salt solution after each dilution. Mix the 
antigen and sera after each dilution by inversion over the index finger. Wipe 
off the tip of the finger with a clean cloth after each mixing. Transfers and 
dilutions, made according to the diagram (Fig. 21) will give in tube 1,1:50; 
tube 2, 1 TOO; tube 3, 1:200; and tube 4, 1:500. 
9. After the dilutions of the sera are made carefully wash the 0.1 cc. pipette 
in salt solution and then in distilled water. 
10. Place the rack holding the tubes in the 37° C. incubator for 48 hours. 
11. Remove the rack and tubes from the incubator. Examine the tubes by 
transmitted light. All tubes in which the bacteria have not settled out have 
not agglutinated. Clumps of bacteria floating in the solution are partly ag¬ 
glutinated. 
12. Compare the dilutions made with the antiserum and with normal serum 
Tabulate the results, by dilutions for the two sera. In the diagnosis of bovine 
contagious abortion agglutinations in dilutions of 1:50 and above indicate a 
positive test. 
13. (a) What is the name of the antibodies used in this exercise? 
( b ) Name two other kinds of antibodies? 
(c) What important human disease may be diagnosed by means 
of this test? 
(d) What name is applied to it when used for the above human 
disease? 
(e) What is the value of such a test as this? 
(/) What substances in the bacteria probably stimulate antibody 
production? 
(g) How may this be related to the specificity of the serological 
tests? 
( h ) Of what value is such a test as this in the classification of 
bacteria? 
