THE COEXEA 335 



agrees to a very great extent with the opsonic teachings of "Wright. He defines 

 the opsonic power of the serum as the power by which the phagocytosis of the 

 bacteria is promoted. 



Treatment by prieumococcal serum is made difficult by the fact that the various 

 strains of Pneumococci show specific differences with regard to the antibodies which 

 they produce. 



Kindborg, 1 in a paper from Frankel's Institute, by sufficiently diluting the 

 immune sera which they had produced, showed that each individual strain of 

 Pneumococci only formed an agglutinin for itself. The agglutinating serum 

 obtained by one strain did not agglutinate the other strains. 



This specific division of the individual strains of Pneumococci was of importance 

 in the immunizing experiments of Kindborg. The immune serum which was 

 obtained by the intravenous injection of large doses of dead cultures protected 

 white mice only against that same strain. Against other strains it was in- 

 effectual. 



Kindborg therefore preferred to speak of ' the Pneumococci ' rather than ' the 

 Pneumococcus,' using the analogy of the Streptococci. 



Scholtz 2 examined the mutual agglutinating power of various strains of Pneumo- 

 cocci from ulcera serpentia, and did not find so sharp a distinction between them ; 

 still, he did find some difference, and his records must be considered. 



Eomer has attempted to meet these individual variations of the various strains of 

 Pneumococci by means of a polyvalent serum produced from as many strains as 

 possible (just as is the case with Menzer's streptococcal serum). But the result 

 has not been satisfactory in the majority of cases. 



This last-mentioned difficulty, which Romer tried to obviate by means of his poly- 

 valent serum, and which is so great a factor in the inconstancy of serum treatment, 

 is alleged to be of less influence in the ' aggressin immunity ' discovered by Bail. 3 

 Bail found that if the peritoneal exudate due to typhoid, when the bacilli had been 

 removed by the centrifuge and filtration, were injected into another animal, it had the 

 power of enormously increasing the susceptibility of the second animal to typhoid : 

 a very much smaller dose of the bacilli was then fatal. He named this power 

 which the exudate possessed ' aggressin.' If now such bacteria-free exudate be 

 repeatedly injected, an ' anti-aggressin ' is formed, causing much higher immunity 

 against the bacilli than could be obtained by any of the other means of bactericidal 

 immunizing. A relatively powerful passive immunity can be produced by 

 injections of the serum of such an animal. 



Hooke 4 applied this method to the Pneumococcus. 



Eomer 5 attempted to apply it to ulcus serpens. It would have been especially 

 important could we have confirmed his hypothesis that the aggressin immunity 

 produced by one strain was capable of protecting against infection with strains of 

 varied origin, and from different ulcera serpentia. Strains of high virulence (for 

 the serum animal), and not merely those pathogenic for man, could then be used 

 in the production of the serum. The methods of treatment by ' polyvalent serum ' 

 heretofore used have only shown partial success, but by this (aggressin) method 

 a better result seems to be more simply obtainable. These expectations have not 

 been realized. 



Wassermann has shown that an analogous action can be produced by living 

 bacteria, to which distilled water has been added (autolysis), or which have been 

 treated with other extracts. 



1 Zeit.f. Hyy. u. Infekt., 1905, iii., p. 97. 



2 A.f. A., 1906, Ivi., p. 84. 3 Zeit.f. Hyg. u. Infekt., 1904. 



4 Wien. Klin. Woch , April, 1905, No. 14, ' Uber Diplokokkenaggressine.' 



5 Hcidel. Cong., 1905, rev. K. M.f. A., September, xliii., Bd. ii. 



