32 VACCINE AND SEKUM THEEAPY 



ally increased by active immunisation with dead 

 bacteria or bacterial products. 



According to the theory of Wright, opsonins are 

 distinct bodies that could not be identified with either 

 complement or antibodies present in the serum. 

 Other workers maintain that the opsonins are nothing 

 more than lytic amboceptors or complement contents 

 of serum. They base this contention not only upon 

 the thermolability of normal opsonins, but also upon 

 the fact that opsonins may be removed from normal 

 serum at the same time as complement by the method 

 of complement fixation. 



Opsonic Index Test.— This test is applied when we 

 wish to determine to what extent phagocytosis is 

 occurring within the animal body in resisting a 

 bacterial infection. The factors necessary for the 

 performance of an opsonic test are (1) the blood 

 serum to be tested ; (2) an even emulsion of bacteria ; 

 (3) leucocytes. Next, equal quantities of corpuscles, 

 bacteria, and serum, which are sucked into a capillary 

 pipette, are mixed thoroughly by the repeated drawing 

 in and out of the pipette's contents upon a glass slide. 

 The mixture is then drawn into the tube, the ends 

 are sealed, and it is placed in an incubator for from 

 fifteen to thirty minutes. A control with normal 

 serum is treated in the same waj^ After incubation 

 the end of the pipette is broken off, the contents again 

 mixed, and then smears are made upon a glass slide. 

 The smear is next stained by any of the bloodstains. 

 The smear is then examined under a microscope, and 



