388 EXPERIMENTAL INFECTIONS DURING LIFE 



Grease pencil. 



Bunsen burner with peep flame. 



Electrical signal clock (see page 39) stop watch, or watch. 



Rectangular glass box or tray to hold pipettes. 



Incubator regulated at 37 C. 



3X1 slides. 



Piece of light rubber tubing. 



Retangular block of plasticine. 



Flask of normal saline solution. 



Flask of sodium citrate (1.5 per cent.) in normal saline solution. 

 Materials required, and their preparation : 



Small tube of "washed cells" (red blood discs and leucocytes); 

 human cells are used in estimating the opsoiiising power of the 

 serum of experimental animals. 



Small tube of emulsion of bacteria of the species responsible 

 for the infection of the experimental animal. 



Blood pipette containing specific serum. 



Blood pipette containing "pooled" serum. 



Washed Cells. 



1. Take a small centrifuge tube and half fill it with 

 sodium citrate solution. Mark with the grease pencil 

 the upper limit of the fluid. 



2 . Cleanse the skin of the distal phalanx of the second 

 finger of the left hand above the root of the nail with 

 lint and ether. Wind the rubber tubing tightly round 

 the second phalanx ; puncture with a sterile Hagedorn 

 needle through the cleansed area of skin. 



3 . Take up a sufficiency of the issuing blood (more or 

 less according to the number of tests to be performed) 

 with a teat pipette, transfer it to the tube of citrate 

 solution and mix thoroughly. Make a second mark on 

 the tube at the upper level of the mixed citrate solution 

 and blood. 



4. Place the tube in the centrifuge, counterpoise 

 accurately and centrifugalise until the blood cells are 

 thrown down in a compact mass occupying approxi- 

 mately the same volume as is included between the 

 two pencil marks. 



The column of fluid in the tube now shows clear 

 supernatant fluid (citrate solution and blood plasma) 



