350 PATHOGENIC MICROORGANISMS 



saprophytic types by the fact that they ferment lactose and salicin, 

 but fail to ferment raffinose, inulin, or mannite. According to their re- 

 sults, the usual saprophytic types found in the mouth either fail to fer- 

 ment salicin or ferment raffinose or inulin, whereas the usual fecal types 

 ferment mannite. They also found in infection mannite fermenters 

 which were apparently of fecal origin. Streptococci which gave the 

 same fermentative reaction as the mouth saprophytes were, however, 

 frequently found in malignant endocarditis. 



Probably the most reliable method of determining the interrelation- 

 ships existing between bacteria, not only within this group, but in p,]! 

 bacterial classes, is that depending upon their reactions to immune 

 sera. The work of Aronson,^ Marmorek,^ and others has shown that 

 streptococcus immune sera produced with any one race of pyogenic 

 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 

 scarlatina more highly than its own microorganism. As with other 

 "group agglutinations," the more highly immune the serimi is, the 

 more general 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 strepto- 

 cocci as a class. 



Streptococcus mucosus. — This microorganism was first definitely 

 described by Howard and Perkins ' in 1901, and was, subsequently care- 

 fully studied by Schottmtiller,* who isolated it from cases of parame- 

 tritis, peritonitis, meningitis, and phlebitis. The organism has since 

 been described by many observers as the incitant of a variety of 

 lesions and as an apparently harmless inhabitant of the normal mouth. 



^Aronson, Berl. klin. Woch., 1902; ibid., 1903. 



2 Marmorek, Berl. klin. Woch., 1902. 



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



* SchoUmiMer, Munch, roed. Wpch., xxi, 1903, 



