within the body. Bordet (40) has shown,' for example, that 

 even v^/hen tne most virulent organisms are injected into a 

 susceptible animal, there is an initial phagocytosis. This 

 he explains as a selective process. Supposing that any 

 culture, no matter how virulent, contains numbers of feeble 

 and weakly aggressive individuals and these the phagocytes 

 at once select and devour. The remaining hi^'^hly selected 

 bacteria then, in some cases, extend the infection without 

 any phagocytic interference. Zinsser (41) likev^ise has pointed 

 out that it is possible to obtain agglutination of "culture" 

 pallida but quite impossible to do so when the spirochetes are 

 taken directly from a lesion. A certain reasonableness therefore 

 attaches itself to tne objection that with phagocytic determin- 

 ations in vitro one m.ay be dealing largely/- with the enfeebled 

 non-pathogenic fraction of the cultures examined and that the 

 findings are v;orthless as an index of vital phagocytic defense. 

 It cannot be denied, hov^^ever, that opsonic determinations possess 

 some significance and diagnostic value. It is possible that such 

 observations in a specific case may be of uncertain value, but 

 when extended over a large series, representing a wide variety 

 in species and conditions, a uniform result gives ample justifi- 

 cation for conservative deductions. 



Perhaps the most striking feature of this investigation 

 has been the unfailinr-- effectiveness of phagocytic activity 

 against the non-specific bacteria. In not one instance has 

 there been any appreciable decline in the opsonic index for any 

 microorganisms not concerned in the primary infection. -^his 



(6}) 



