OPSONINS 285 



chiefly of leucocytes. These are pipetted off with a capillary pipette 

 (by careful superficial scratching movements over the surface of the 

 buffy coat). 



There being, of course, no absolute scale for phagocytosis, whenever 

 an opsonin determination is made upon an unknown serum, a parallel 

 control test must be made upon a normal serum. This normal is best 

 obtained by a "pool" or mixture of the sera of five or six supposedly 

 normal individuals. 



The three ingredients — serum, bacterial emulsion, and leucocytes — ■ 

 having thus been prepared, the actual test is carried out as follows: 



Fig. 67. — Pipette fob Opsonic Work. 



Capillary pipettes of about six or seven inches in length and of nearly 

 even diameter throughout, are made. These are fitted with a nipple 

 and a mark is made upon them with a grease-pencil about 2 to 3 cm. 

 from the end (Fig. 68). Corpuscles, bacteria, and serum are then 

 successively, in the order named, sucked into the pipette up to 

 the mark, being separated from each other by small air-bubbles. Equal 

 quantities of each having thus been secured, they are mixed thoroughly 

 by repeatedly drawing them in and out of the pipette upon a sHde. 

 The mixture is then drawn into the pipette; the end is sealed; and 

 incubation at 37.5° is carried on for an arbitrary time, usually fifteen 

 to thirty minutes.' The control with normal serum is treated in exactly 



Fig. 68. — Pipette with three Substances, Corpuscles, Bacteria, and Serum, 



AS first taken up. 



the same way. After incubation the end of the pipette is broken off, 

 the contents are again mixed, and smears are made upon glass slides in 

 the ordinary manner of blood smearing. Staining may be done by 

 Wright's modification of Leishman's stain, by Jenner's, or by any other 

 of the usual blood stains. In these smears, then, the number of bacteria 

 contained in each leucocyte is counted. The contents of about eighty 



' For the purpose of incubation, specially constructed water baths, marketed under 

 the name of " opsonizers," may be used. 



