ESTIMATION OF THE OPSONIC CONTENT OF THE BLOOD 207 



blood to be examined, in place of 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 6, 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 (ra) 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 tip at s, the capsule is inverted, when the blood will occupy the 

 space above s. The aperture at s is again sealed, and the serum now 

 separated from the corpuscles by centrifugation, to which end the 

 capsule is suspended on the rim of the centrifugalizing tube by the 

 bent limb. In the end the tube is cut with a file at n. 



Preparation of the Normal Control Serum. This is collected in the 

 same manner as the patient's serum and separated from the corpus- 

 cles by centrifugation. It is best to pool three or four normal sera, 

 viz., to mix equal quantities from three or four individuals. If, 

 however, the serum of one single person (the experimentor, for 

 example) has been thoroughly studied and always found normal, 



