350 PATHOGENIC MICROORGANISMS 



streptococci exerted considerable, though variable, protective action 

 against many other strains of streptococci. The same authors, as well 

 as many others, working with the agglutination reaction, have shown 

 that the agglutinins produced with one streptococcus strain were active 

 against many other streptococci. While most active usually against 

 the particular microorganism with which they were produced, this was 

 by no means the rule, a serum produced with a streptococcus from a case 

 of sepsis, in one case, agglutinating a streptococcus from a case of scar- 

 latina more highly than its own microorganism. As with other "group 

 agglutinations," the more highly immune the serum is, the more gen- 

 eral is the agglutinating power over the whole group. Thus, while 

 agglutination is practically useless in separating streptococci from one 

 another, it is highly useful in differentiating these organisms from allied 

 groups, such as the pneumococci. The immune reactions, therefore, 

 seem to indicate a very close relationship between streptocococci as a class. 



Pneumococcus (streptococcus) mucosus. First definitely de- 

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

 studied by Schottmuller, 2 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 le- 

 sions and as 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 persist- 

 ence. 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 masses. The 

 regularity with which this microorganism ferments inulin medium, 

 make it probable that it is more accurate to place it with the group 

 of pneumococci than with that of streptococci. 3 



Most of the organisms of this group show the common characteris- 

 tics of the pneumococci and are soluble in bile. Occasional strains, 

 such as one studied by Dochez and Gillespie, neither ferment inulin 

 nor are bile soluble. Rarely, too, does it cause hemolysis. From the 

 various studies carried out upon this group it must be concluded that 

 while perfectly distinct in its formation of a heavy mucoid colony and 

 capsulation, this group is more closely related to the pneumococci than to 



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



2 Schottmuller, Munch, med. Woch., xxi, 1903. 



3 Hiss, Jour. Exp. Med., 1905; Buerger, Cent. f. Bakt., I, xli, 1906. 



