240 THE ACUTE PNEUMONIAS 



pneumonia by serum derived from immune animals, and appar- 

 ently with a certain measure of success, and sera prepared by 

 Washbourn and by others have also been used. The results 

 obtained by different observers have, however, been rather con- 

 tradictory. The use of these sera apparently causes the tempera- 

 ture in some cases to. fall, and even may hasten a crisis, but 

 further experience is necessary before their value in therapeutics 

 can be properly estimated. 



There has been considerable difference of opinion as to the 

 explanations to be given of the facts observed regarding im- 

 munisation against the pneumococcus and especially regarding 

 the properties of immune sera. At first these sera were supposed 

 to possess antitoxic qualities largely on the ground that no 

 bactericidal effect was produced by them on the bacterium in 

 vitro. As no specific toxin has been proved to be concerned in 

 the action of the organism, the development of an antitoxin 

 during immunisation must, in the present state of knowledge, 

 be looked on as not yet proved. To explain the action of a 

 serum in preventing and curing pneumococcal infections, it has 

 been thought to have the complex character seen in anti-typhoid 

 sera in which two substances immune body and complement 

 (see Immunity) are concerned, and the variability in the 

 therapeutic results obtained has been accounted for on the view 

 that there might be a deficiency of complement, such as occurs 

 in other similar cases. The absence of bactericidal effect, how- 

 ever, raises several difficult points. It is stated that no such 

 effect is observable either in immune sera, or in the serum of 

 patients who have successfully come through an attack of the 

 natural disease. Some effect of the kind would be expected to 

 be present if the anti-pneumonic serum were quite comparable 

 to the anti-typhoid serum. Within recent times many have 

 turned to the opsonic property of sera to account for the facts 

 observed. In this connection Mennes observed that normal 

 leucocytes only become phagocytic towards pneumococci when 

 they are lying 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 Rlmpau have described the occurrence of an 

 opsonic effect in the action of an anti-pneumococcic serum. 

 Further work may show that along these lines lies the explana- 

 tion of the facts observed. 



In studying further the relationship of the opsonic effect to 

 pneumococcal infection, inquiry has been directed to the opsonic 



