218 BIOLOGY AND TECHNIQUE 



of people examined harbored pneumococci in their mouths, at one 

 time or another, in the course of the cold months. Since then, the 

 typing of the pneumococcus has made it possible to show that the 

 pneumococci most frequently present in the mouth belong to Group 

 IV. In the investigations of Dochez and Avery which are described 

 in another place, it was found that this type caused only about 9.8 

 per cent of pneumonias, but was found with considerable frequency 

 in normal mouths. The other and more virulent types may be found 

 in the normal mouth, as well, but are more apt to represent recent con- 

 tact with pneumonia cases or a transitory carrier state. This, at least, 

 is suggested by the writers mentioned above, though probably a 

 definite, conclusive statement cannot be made concerning it at the 

 present time. 



Of the non-pathogenic Gram-positive cocci the Micrococcus Candi- 

 cans and occasional pigment forming micrococci are not infrequent. 



Micrococcus Tetragenus is very often an inhabitant of the mouth 

 and, as a matter of fact, one sees it most frequently in routine work 

 in Loeffler's cultures taken for the purpose of diphtheria diagnosis. 



Of Gram-negative micrococci there is a considerable variety which, 

 without being pathogenic, may be cultivated from the mouth and 

 throat and add no little confusion to meningococcus carrier examina- 

 tions. Most common among these are the Micrococcus Catarrlialis, 

 which is described in another section, and may be distinguished from 

 the meningococcus by its heavier growth, its growth at room tem- 

 perature and its failure to produce fermentation of dextrose and 

 maltose. The Micrococcus Flavus, which frequently has led to error 

 in similar work, is a pigment forming Gram-negative coccus often 

 found in the throat, which grows at room temperature, and in most 

 cases agglutinates spontaneously in normal horse serum. Another 

 which forms very dry colonies, the Micrococcus Pkaryngis siccus, is 

 often isolated, but easily recognized. In addition to this, Elser and 

 Huntoon have described three different chromogenic groups of similar 

 organisms often found in the mouth and throat. These probably do 

 not exhaust all the possible Gram-negative micrococci that can be 

 isolated from this locality, but it is really only of importance to make 

 sure in human examination whether one is dealing with a true 

 meningococcus, with a micrococcus catarrhalis, or with other sapro- 

 phytes. 



True meningococci are of course often found in normal or slightly 

 inflamed throats during the carrier state, which is discussed at con- 



