258 , PHAGOCYTOSIS— OPSONINS 



than from 0.8 to 1.2, and that an index below 0.8 may show 

 a great susceptibUity for the organism tested, infection with 

 the given organism if derived from the individual, or improper 

 dosage in case attempts have been made to immunize by 

 using killed cultures, vaccines, of the organism. 



On the occasion of the author's visit to Wright's clinic 

 (1911) he stated that he used the determination of the opsonic 

 index chiefly as a guide to the dosage in the use of vaccines. 



Most workers outside the Wright school have failed to 

 recognize any essential value of determinations of the 

 opsonic index in the use of vaccines. Some of the reasons 

 for this are as follows: The limit of error in phagocytic 

 counts may be as great as 50 per cent, in different series of 

 fifty, hence several hundred must be counted, which adds 

 greatly to the tediousness and time involved; the variation 

 in apparently healthy individuals is frequently great, hence 

 the "normal" is too uncertain; finally the opsonic index 

 and the clinical course of the disease do not by any means 

 run parallel. Undoubtedly the method has decided value 

 in the hands of an individual who makes opsonic determina- 

 tions his chief work, as Wright's assistants do, but it can 

 scarcely be maintained at the present time that such deter- 

 minations are necessary in vaccine therapy. Nevertheless 

 that opsonins actually exist and that they play an essential 

 part in phagocytosis, and hence in immunity, is now generally 

 recognized. 



BACTERIAL VACCINES. 



Whether determinations of opsonic index are useful or 

 not is largely a matter of individual opinion, but there is 

 scarcely room to doubt that Wright has conferred a lasting 

 benefit by his revival of the use of dead cultures of bacteria, 

 hacterial vaccines, both for protective inoculation and for 

 treatment. It is perhaps better to use the older terms 

 "vaccination" and "vaccine" (though the cow, vacca, is not 

 concerned) than to use Wright's term "opsonic method" in 

 this connection, bearing in mind that the idea of a vaccine 

 is that it contains the causative organism of the infection as 

 indicated on p. 231 . 



