448 PATHOGENIC MICROORGANISMS 



and llx. All of these are proven members of type II because they all 

 agglutinate in concentrated type II serum. All but llx are protected 

 against by type II serum. Absorption of type II serum with a type II 

 organism removes the antibodies for all the subgroups. Absorption 

 of the anti-pneumococcus type II serum with any one member of a 

 subgroup removes only the antibodies for that particular subgroup. 



That the three subgroups are specifically different from each other 

 and from type II, is determined by Avery by the fact that any given 

 subgroup is not agglutinated by antisera made with organisms of the 

 other two subgroups. The same is true of protection reactions. Also, 

 no one of them absorbs the antibodies for the other subgroups from 

 serum. 



Subgroups "A" and "B" have immunity reactions identical, each 

 within its respective group. Subgroup IIx, however, consists of heter- 

 ogeneous strains in which each strain seems to produce its character 

 istic antibodies specific only for the strain used. 



In addition to these types, there are unquestionably a number of 

 other types in different parts of the world. Thus, Lister 33 working in 

 South Africa, found three homogeneous types, A, B, C, his types C 

 and B corresponding to types I and II of the American classification, 

 respectively; his type A being not so far identified with any of our 

 American types. 



The importance of this discovery of the serological pneumococcus 

 group in serum therapy is obvious, and its bearing on epidemiology is 

 dealt with in another section. 



Pneumococcus (streptococcus) Mucosus. First definitely de- 

 scribed by Howard and Perkins 34 in 1901, and subsequently carefully 

 studied by Schottmuller, 35 who isolated it from cases of parametritis, 

 peritonitis, meningitis, and phlebitis. It has since been described by 

 many as the incitant of lobar pneumonia and of a variety of other 

 lesions and as often an apparently harmless inhabitant of the normal 

 mouth. Morphologically, though showing a marked tendency to form 

 chains, on solid media it often appears in the diplococcus form. It is 

 enclosed in an extensive capsule, which appears with much regularity 

 and persistence. Though very similar in appearance, therefore, to 

 pneumococci, these bacteria do not appear in the typical lancet shape. 

 Upon solid media they show a tendency to grow in transparent moist 



33 Lister, Pub. South African Inst. for Med. Res., 1916, No. 8. 

 "Howard and Perkins, Jour. Med. Res., 1901, N. S., i. 

 85 ScJiott mutter, Munch, med. Woch., xxi, 1903. 



