382 EXPERIMENTAL INFECTIONS DURING LIFE 



METHOD. 



1. Take three sterile test-tubes and number them i, 

 2 and 3. 



2. Pipette 0.9 c.c. sterile normal saline solution into 

 each tube, and stand tubes upright in the sand in the 

 capsule, or in the plasticine block. 



3 . Make a scratch with the glass cutting knife on the 

 blood pipette above the upper level of the clear serum, 

 and snap off and discard the empty portion of the tube. 



4. Remove o.i c.c. of the serum from the blood 

 pipette tube, and mix it thoroughly with the fluid in 

 tube No. i ; and label s.s., (specific serum), 10 per cent. 



5. Remove o.i c.c. of the solution from tube No. i 

 by means of a fresh pipette, and mix it with the con- 

 tents of tube No. 2 ; and label s.s., i per cent. 



6. Remove o.i c.c. of the solution from tube No. 2 

 by means of a fresh pipette, and mix it with the con- 

 tents of tube No. 3 ; and label s.s., o.i per cent. 



When the yield of serum from the specimen of blood 

 which has been collected, or is available, is small, the 

 above method of diluting is not practicable, and the 

 dilution should be carried out by Wright's method 

 in a capillary teat pipette. 



Dilution of Serum by Means of a Teat Pipette. 



Materials required: 



Blood pipette containing sample of specific serum after centrif- 

 ugalisation. 



Capsule of diluting fluid normal saline solution. 



Supply of Pasteur pipettes (Fig. 130). 



India-rubber teats. 



Small test-tubes. 



A block of plasticine to act as a test-tube stand. 



Grease pencil. 



METHOD: 



i . Mark three small test-tubes 10 per cent., i per cent, 

 and o.i per cent, respectively, and stand them upright 

 in the plasticine block. 



