OPSONINS 133 



Thus the author l finds that the variation in the 

 opsonic indices of several normal persons is often 

 considerable; that opsonic counts based on fifty 

 leucocytes may occasionally vary by more than 

 50% and that it is therefore necessary to count from 

 150 to 200 leucocytes for each test; that duplicate, 

 triplicate and more tests made of the same serum, 

 at the same time, and under identical conditions so 

 far as one can tell, frequently give widely divergent 

 results; that the opsonic index and the clinical 

 course of the disease do not always run parallel. 

 Cases may do very well and have the index remain 

 low; other cases may do poorly with an increased 

 opsonic index. It is to be noted, furthermore, that 

 some of these variations in results are unavoidable, 

 at least with the present technique. 



To one who has followed the progress of immunity 

 studies, it is not at all surprising to find that the 

 opsonic index is not necessarily a measure of the 

 patient's immunity. When Gruber and' Durham 

 published their observations on agglutinins the 

 phenomenon was at once hailed and interpreted by 

 many as measuring the degree of immunity possessed 

 by the patient. The same error was made when 

 some time later the bacteriolytic substances were 

 discovered. In both cases it was soon found that 

 these were but accompaniments of greater or less 

 significance to the complex phenomenon of immun- 

 1 Bolcluan, Long Island Med. Journal, VoJ. i, 1907, 



