27 



of lobar pneumonia — Type I 33*3 per cent. Type IT 29*3 per 

 cent. Type III 13 per cent. Type IV 20*3 per cent, and 

 Atypical Type II 4* 2 per cent. 



Atypical Pneumococcal 



As will be seen from the above table, 45 strains of pneumococci 

 from cases of lobar pneumonia failed to agglutinate with any 

 of the type sera I, II and III Such strains which did not 

 conform to any of the three chief types were at first classed by the 

 American workers as " Type IV " and it was thought that they 

 were all serologically unrelated. In their later investigations 

 these atypical strains were found to include a number of serological 

 types, some of which could be shown by the use of concentrated 

 Type II serum to be related to that type. These latter strains 

 were therefore designated atypical Type IIa, IIb, etc. I have 

 obtained from the Rockefeller Institute examples of types IIa 

 and IIb and have prepared sera from them. As will be seen 

 below, these two types appear to occur in cases of lobar pneu- 

 monia in this country next in order of frequency to the three fixed 

 types. When moderate dilutions of strong agglutinating sera are 

 used, there is no cross agglutination between the strains of Types 

 II, IIa and IIb and their respective sera ; they appear to be quite 

 distinct serologically. Moreover Type II serum does not confer 

 protection on mice against the atypical Type II strains. The 

 evidence of the relationship that can be demonstrated by the use 

 of concentrated Type II serum is of doubtful significance. For 

 the present, therefore, I propose to include all the " atypical II " 

 strains in the same category as the American heterogeneous 

 " Type IV " and to term them collectively Group IV. In order 

 to facilitate comparison with the results of other workers I have 

 retained the designations, types IIa and IIb. 



I have prepared agglutinating sera from a number of the 

 atypical strains, or strains of Group IV with the object of 

 attempting a serological classification of the group. After a 

 preliminary test with these sera it was found that, while some 

 of the strains used were of the same type, many of the Group IV 

 pneumococci failed to agglutinate with any of the sera so far 

 prepared. A further selection from the non-reacting strains 

 was made and sera were produced with them. So far I have 

 obtained sera of a sufficiently high agglutinating titre with 12 

 serologically different types of Group IV (including the American 

 Types IIa and IIb). 



The American workers have shown that the atypical strains occur 

 frequently in the normal mouth and in respiratory conditions other than 

 lobar pneumonia, whereas Types I and II are rare in such circumstances. 

 During the present inquiry into the types of pneumococci occurring in 

 lobar pneumonia, a number (40) of strains were obtained from the sputum 

 of other cases of disease, principally of respiratory origin, e.g., broncho- 

 pneumonia, influenzal pneumonia, influenza, bronchitis, coryza, &c. From 

 certain of these, selected on account of their high virulence for mice, sera 

 were prepared which have been used to test the Group IV pneumococci 

 from cases of lobar pneumonia. In the case of each of such strains at 



