MICHIGAN ACADEMY OF SCIENCE. 
1 15 
Fig. 3. — Special blood 
pipette. 
strength of saline solution for diluting tubercle and 
gonococcus is 14 percent; the strength to use for most 
other germs is 0.85 per cent. 
Preparing the Washed Blood-corpuscles . — Things re- 
quired: an ordinary gauze bandage or a piece of light 
rubber tubing; IT per cent* sodium citrate solution; a 
special blood pipette (see Fig. 3) ; two blood capsules 
(see Fig. 4). The capsules may be of various sizes 
and shapes, depending on the amount of corpuscles re- 
quired, and upon the character of the centrifuge to 
be used. Fill two capsules three-quarters full of the 
sodium citrate solution; make a pricking needle by 
drawing out the long capillary arm of the pipette in 
a pilot flame (see Figs. 5 and 6), wind the thumb cen- 
trifugally with the bandage or rubber tube in order 
to cause marked congestion in the tip. Prick the 
thumb with the glass needle (see Fig. 6) — preferably 
at the root of the nail — and allow the blood to flow 
into one or both of the capsules containing sodium 
citrate solution (see Fig. 7). Mix the blood and 
citrate solution, and, having balanced the tubes 
carefully, centrifugalize until the corpuscles are thrown 
down (see Fig. 4). Remove the supernatant sodium 
citrate solution carefully with a pipette, and wash 
the corpuscles in 0.85 per cent sodium chloride solu- 
tion. Again centrifugalize and remove the saline as completely as pos- 
sible. The last drop of saline can be best removed by inclining the tube 
and drawing the saline into a capillary pipette from the back portion of 
the meniscus (see Fig. 8). 
During the time that the blood is flowing into the 
capsule it can be conveniently mixed with the citrate 
solution by occasionally raising the closed end of the 
capsule while the open end is kept well pressed against 
the thumb. The bubble of air passing from end to 
end of the tube thoroughly mixes the fluids. Similarly 
the corpuscles can be washed in the sodium citrate so- 
lution by closing the mouth of the tube and alter- 
nately inverting it. The air bubble will gently but 
efficiently wash the corpuscles. Vigorous shaking of 
the blood-corpuscles is to be avoided. 
Preparing/ the Serum . — Bleed the finger, as before, 
allowing the blood to flow into the special blood 
pipette (see Fig. 9). Seal the needle end of the blood 
_ pipette (see Fig. 10), and when cool shake the blood 
before" arid aftT^celuri- down into this end (see Fig. 11). Place in the incu- 
fugaiizing. bator for fifteen to thirty minutes, and, if the serum 
be not clearly separated by the end of this time, centrifugalize it 
(see Fig. 12). It frequently happens that the surface of the blood clot 
dries and adheres to the inner surface of the glass tube so firmly that it cannot 
be thrown down in the centrifuge. In such case break off the curved end 
* A solution containing 8.5 grm. sodium chloride and 5 grin, sodium citrate per liter also gives 
good results. 
