GENERAL BACTERIOLOGY 
65 
The clotted portions of the blood are stirred up with 
a wire and put in an ice box for the serum to separate 
from the slot. The portions received in the citrate or 
normal salt solution are “washed’’ three times (“wash¬ 
ing” red blood cells consists of centrifugalizing the 
tubes for two or three minutes when the cells will be 
found packed on the bottom of the tube, pouring off 
the supernatant fluid, then pouring on some more of 
the normal salt solution and centrifugalizing again) ; 
after the third washing, enough salt solution is added 
to make the cells a 10% solution. 
The actual test is carried out as follows: Six 4x^2 
centimeter test tubes (the so-called Wassermann tubes) 
are placed in a test tube rack, and to each one 1 c.c. of 
normal salt solution is added. 
The first tube receives 0.1 c.c. of the recipient’s 
(patient’s) cell emulsion and 0.2 of the donor’s serum. 
The second tube receives 0.1 c.c. of the donor’s cell 
emulsion and 0.2 of the recipient’s serum. 
The above two tubes are for the actual test; the 
following four tubes are the controls: 
The third tube receives 0.1 c.c. of the recipient’s cell 
emulsion and 0.2 c.c. of the recipient’s serum. 
The fourth tube receives 0.1 c.c. of the donor’s cell 
emulsion and 0.2 c.c. of the donor’s serum. 
The fifth tube receives only 0.1 c.c. of the recipient’s 
cell emulsion. 
The sixth tube receives only 0.1 c.c. of the donor’s cell 
emulsion. 
The tubes are now incubated for thirty minutes at 
37.5° C. At the end of this time they are taken out, 
shaken throughly, and re-incubated for thirty minutes 
longer, and examined again. The last four tubes—the 
control tubes—will show neither hemolysis nor agglutina- 
