WASHING ERYTHROCYTES 



29 



be placed in centrifuge tubes and five to ten volumes of sterile normal 

 salt solution added and thoroughly mixed. Tubes are then carefully 

 balanced and centrifuged at moderate speed for five minutes. 



2. Remove the supernatant fluid down to the corpuscles with a 

 sterile pipet. Add an equal volume of salt solution; mix the corpuscles 



FIG. 9. A SUCTION PUMP. 



By attaching a capillary pipet to the rubber tubing fluid may be removed without 



disturbing the sediment. 



and centrifuge. This process should be repeated once more in order to 

 insure thorough washing of the corpuscles to remove all traces of serum. 

 For removing supernatant fluids which are to be discarded, the suction 

 pump shown in Fig. 9 will be found very useful. It is well to fit the 



