SERUM REACTIONS 249 



in the serum of an animal immunised against this bacterium. 

 Wright had in his early papers looked to the phagocytosis of 

 sensitised bacteria to explain their destruction in the absence 

 of bactericidal qualities in the serum alone, and Neufeld and 

 Rimpau have described the occurrence of an opsonic effect in the 

 action of an anti-pneumococcic serum. Here again, however, 

 our knowledge cannot be said to be definite. 



In studying further the relationship of the opsonic effect to 

 pneumococcic infection, inquiry has been directed to the opsonic 

 qualities of the blood of pneumonic patients, especially with a 

 view to throwing light on the nature of the febrile crisis, the 

 essential nature of which is, however, still entirely obscure. 

 According to some results, the opsonic index as compared with 

 that of a healthy person is not above normal, but if the possible 

 phagocytic capacities of the whole blood of the sick person be 

 taken into account, these will probably be much above normal 

 in consequence of the leucocytosis which usually accompanies a 

 successful resistance to this infection. It has been observed, 

 however, that as the crisis approaches in a case which is to 

 recover, the opsonic index rises, and after defervescence gradually 

 falls to normal. As bearing on the factors involved in the 

 successful resistance of the organism to the pneumococcus, it 

 has been noted that avirulent pneumococci are more readily 

 opsonised than more virulent strains. It is further stated that 

 avirulent cultures of the pneumococcus can be made to resist 

 phagocytosis if they are treated with the products of the 

 autolysis of virulent strains or with washings from such strains, 

 and that virulent cocci if washed with saline become capable of 

 being readily phagocyted. It may be noted here, in conclusion, 

 that in man it is probable that immunity against pneumonia may 

 be short-lived, as in a good many cases of pneumonia a history 

 of a previous attack is elicited. 



The difficulty of interpreting the various serological facts 

 observed in pneumonic conditions has led Lamar to investigate 

 the action of certain chemical bodies, belonging to the soaps, on 

 pneumococci. Welch long ago observed changes in the proto- 

 plasm of pneumococci in pneumonic exudates, pointing to the 

 occurrence of lysis. Lamar has found that pneumococci treated 

 with sodium oleate and especially with potassium soaps of acids 

 having a high iodine value e.g., linoleic and linolenic acids 

 undergo morphological changes and become more subject to 

 autolysis and more sensitive to the lytic action of sera, the latter 

 being especially evident when immune sera are employed. The 

 action of the soap is probably exerted on the lipoidal moiety of 



