17 



minutes in boiling water, cooled under running water, and 

 neutralised with normal NaOH. 



In 1919, Nicolle and Debains* discussed the principles on 

 which their classification was based and gave their results in 

 detail. Their theory Avas an amplification of the " mosaic 

 pattern " conception of antigens. Every bacterium contained 

 an unknown number of certain constituents, termed antigens, 

 which were capable of producing agglutinins and lysins in the 

 animal body. The apparent isolation of an antigen merely 

 meant that one antigen was found to predominate and to obscure 

 the other antigens which were also present and might be demon- 

 strated by other methods. Thus, agglutination emphasised a 

 particular antigen and so formed the criterion for racial charac- 

 teristics, whereas the " fixation " test revealed the existence of 

 all the antigens characteristic of the species, and so formed the 

 criterion for the determination of species. Antigens were the 

 units (" corps simples ") of immunology, not the exclusive 

 properties of particular cells. Thus there was nothing surprising 

 to find that certain antigens were common to pneumococci, 

 streptococci and cholera vibrios; and it was wrong to explain 

 the serological demonstration of this fact as due to " heterologous " 

 action. 



They tested the agglutinability of a large number of strains 

 of pneumococci (all bile-soluble) and found that 7 per cent, 

 were hyperagglutinable (i.e., agglutinated in normal serum), 48 

 per cent, were agglutinable without treatment, and 45 per cent, were 

 agglutinable after treatment by their modified Porges' method. 

 For the preparation of their sera they selected four standard 

 strains, designated I, II, II, IV. The first three corresponded 

 with the American I, II and III. Their IV was a special type, 

 isolated from negroes and therefore not to be confused with 

 the heterogeneous American " Type IV." With these strains 

 Truche immunised horses and obtained sera each of which 

 acrolutinated only its homologous strain. Their classification 

 was as follows : — 



Agglutinable Pneumococci. — Pure types : 70 per cent., viz. : — 

 I, 1 per cent. ; II, 32 per cent. ; III, 59 per cent. ; IV, 8 per cent, 

 Mixed types : 30 per cent. viz. : — I + II (I dominant), 64 per 

 cent, ; ' ; without dominance," 9 per cent. ; II -f- HI (II dominant) 

 9 per cent, ; IV + II (IV dominant), 9 per cent. ; I + II -f IV 

 (I and II dominant), 9 per cent, 



Pneumococci Inagglutinable before Treatment. — Pure types : 

 91 per cent., viz. : — I, 9 per cent. ; II, 82 per cent, ; III, 3 per 

 cent, ; IV, 6 per cent. Mixed types : 9 per cent,, viz. : — II + I 

 (II dominant), 33-3 per cent.; II + IV (II dominant), 33-3 per 

 cent,; II + IV (" without dominance "), 33-3 per cent. 



Hyperagglutinable Pneumococci. — II dominant, 60 per cent. ; 

 II + IV dominant, 40" per cent. 



* Bidl. de VAcad. de Med., p. 843. 



