214 ACTIVE IMMUNIZATION 



ESTIMATION OF THE OPSONIC CONTENT OF THE BLOOD 

 (WRIGHT'S METHOD) 



Before concluding this chapter it may not be out of place to give 

 a brief account of the technique which Wright recommended for 

 the purpose of estimating the opsonic index, but which at present 

 has but little more than historical interest, insofar as its bearings 

 on treatment or diagnosis are concerned. The necessary apparatus is 

 pictured in the accompanying illustration (Plate III). It consists 

 of a pipette (a) for collecting corpuscles; (6) a tube to receive the 

 blood to be examined, in place in which the blood capsule (c) can 

 also be used; and capillary pipettes (d and e) provided with rubber 

 nipples. For purposes of incubation a special thermostat is recom- 

 mended, but in its absence the usual laboratory incubator may be 

 employed. The actual "reagents" are represented by the patient's 

 serum, a normal control serum, washed leukocytes, and bacterial 

 emulsions. 



Preparation of the Patient's Serum. A small amount of blood 

 (about 6 or 8 drops) is collected in a little tube like the one pictured 

 in Plate III at b, by puncturing the lobule of the ear at its free 

 margin, in the usual manner, and dipping up the blood as it is 

 milked out by moderate pressure. The little tubes measure about 

 two inches in length and have a diameter of one-quarter of an inch; 

 they may be closed with a little stopper or with adhesive plaster, 

 and can then be readily transported. The blood is allowed to clot, 

 the coagulum separated from the walls of the tube by means of a 

 platinum wire, and the specimen centrifugalized until the corpuscles 

 have been packed down and well separated from the serum. 



In place of the tubes just described, which are really most con- 

 venient, Wright employs special capsules like the one pictured in 

 Plate III at c, both ends of which are sealed. The blood is collected 

 by puncturing the thumb near the root of the nail, after having 

 previously allowed the arm to hang down and then applying some 

 constriction behind the distal joint (tape, rubber tubing). The 

 puncture is made with the sharp point (s) of the straight limb of the 

 capsule. The sealed tip (m) of the bent limb is knicked off and the 

 open end held to the exuding drop of blood which enters by capillary 

 attraction until it reaches the mark n. After knicking off the sealed 



