324 DISTRIBUTION OF BACTERIA 



described in any position has been found in the human mouth. 

 As a matter of fact, about fifty species of bacteria have been 

 isolated and cultivated from the mouth. The connection of 

 the mouth with the exterior accounts for the large flora pres- 

 ent. The bacteria usually enter by inhalation through the 

 mouth, by food or by drink. They may be introduced in- 

 directly by being inhaled through the nose and also post- 

 nasal discharges containing bacteria may find their way into 

 the mouth. 



There are a large number of species of bacteria whose pres- 

 ence in the mouth is accidental, and there are also several 

 species which are found rather constantly. To the latter 

 class of organisms the name " mouth bacteria " has been 

 given by some investigators. As far as is known these bacteria 

 produce no deleterious effect on the body. Bacteriologists 

 have been unable to cultivate these " mouth bacteria," and 

 consequently very little is known about their biology. The 

 origin of these bacteria is unknown. 



A large amount of research work on the bacteria of the 

 mouth was done by Miller in the early periods of bacterio- 

 logical work. The following bacteria were isolated and 

 named by him : Leptothrix 1 innominata, Leptothrix buc- 

 calis maxima, lodococcus-vaginatus, 2 Spirillum sputigenum, 

 Spirochaeta dentium, and Bacillus buccalis maxima. Lep- 

 tothrix buccalis maxima is the organism supposed to have 



1 Leptothrix is a term which was applied to filamentous bacteria. 



2 lodococcus is a coccus form of bacteria not unlike the micrococci. 



