274 



The Phagocytic Power of the Blood 



The blood from the puncture is allowed to flow into the bent 

 end of the tube, into which it enters by capillary attraction and 

 from which it descends to the body of the tube by gravity. At 

 least I cc. of the blood is required to 

 furnish the serum. The ends of the 

 tube are closed in the flame and the 

 tube stood in the thermostat for fifteen 

 to thirty minutes. Coagulation takes 

 place almost immediately, and the serum 

 usually separates quickly. If it does not 

 do so, Wright recommends hanging the 

 curved arm of the tube over the cen- 



Fig. 98. — Special blood pipetet (Miller). 



trifuge tube and whirUng it for a mo- 

 ment or two, when the clot is driven 

 into the straight arm of the tube and 

 the clear serum appears above. The 

 tube is then cut with a file so that the 

 serum can be removed when needed. 

 Mixing the factors concerned in the test 

 is a matter that requires practice and 

 a steady hand. It is best done, as rec- 

 ommended by Wright, in a capillary tube controlled by a rubber 

 bulb. The object of the experimenter is to take up into this pi- 

 pette equal quantities of the creamy layer of blood-corpuscles, of 



Fig. 99. — Opsonizing pipette 

 containing blood-corpuscles, 

 bacterial emulsion, and blood- 

 serum (Miller). 



