CHAPTER II 

 METHODS OF OBTAINING HUMAN AND ANIMAL BLOOD 



As a general rule, when blood is withdrawn to obtain serum a care- 

 ful aseptic technic should be employed. Similarly, when erythrocytes 

 are to be obtained for purposes of immunization it is necessary to avoid 

 contamination by proper cleansing of the parts and the use of sterile 

 needles, containers, and solutions. In obtaining erythrocytes for mak- 

 ing hemolytic tests it is not necessary that the blood be absolutely 

 sterile, the ordinary precautions against gross contamination being 

 sufficient. 



Blood may be withdrawn to obtain the corpuscles or serum or both. 



OBTAINING CORPUSCLES 



Red blood-corpuscles are usually obtained and washed free of serum 

 for the purpose of making hemolytic reactions and experiments. 



Leukocytes are usually obtained for the purpose of estimating the 

 opsonic index. The special technic for obtaining leukocytes for this 

 test is given on p. 198. 



Larger quantities of leukocytes are obtained by injecting sterile 

 irritants, such as sterile aleuronat suspension, into the pleural or ab- 

 dominal cavities of suitable animals. (See p: 204.) 



(a) Blood may be withdrawn and placed at once in two or three 

 volumes of 1 per cent, sodium citrate in 0.85 per cent, salt solution. 

 Clotting is prevented, and the corpuscles- are secured by centrifugaliza- 

 tion or by sedimentation in the refrigerator. 



(b) Blood may be drawn into a beaker or flask and defibrinated at 

 once by whipping with a rod or shaking with glass beads. When the 

 fibrin has been removed, the corpuscles and serum are secured by cen- 

 trifugalization. 



WASHING ERYTHROCYTES 



For purposes of immunization or in making hemolytic tests red 

 blood-corpuscles are washed free of serum before being used. 



1. Place the citrated blood, which has previously been diluted with 

 sufficient salt solution, in centrifuge tubes. Defibrinated blood may 



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