GPSONJNS 



remember Bordet's objections to the assumption 

 of two groups in the agglutinin molecule. These 

 have already been considered on page 40. 



The Opsonic Index. In the study of these opso- 

 nins Wright developed the idea that they were 

 highly important in combating a number of bacterial 

 infections, such as staphylococcus and tubercle. 

 His observations showed that inoculations of the 

 corresponding bacteria produced marked changes in 

 the opsonic contents of the infected individual and 

 that it was possible to estimate accurately the im- 

 munizing effect of such inoculations. 



Technique. Wright's technique of measuring the 

 opsonic power is a slight modification of the Leish- 

 man 1 method and is as follows : An emulsion of 

 fresh human leucocytes is made by dropping twenty 

 drops of blood from a finger prick into 20 c.c. 

 normal salt solution containing one per cent sodium 

 citrate. The mixture is centrifuged, the supernatant 

 clear fluid removed and the upper layers of the sedi- 

 mented blood cells transferred by means of a fine 

 pipette to 10 c.c. normal salt solution. After cen- 

 trifuging this second mixture the supernatant fluid 

 is pipetted off and the remaining suspension used 

 for the opsonic tests. Such a " leucocyte emulsion, ' 

 of course, contains an enormous number of red 

 blood cells; the proportion of leucocytes, however, 

 is greater than in the original blood. 



1 Leishman, British Medical Journal, Jan., 1902. 



