THE BACTERIA OF THE HUMAN BODY 325 



been seen by Anton von Leewenhoek and described by him 

 as an animalcule in a communication to the Royal Society 

 of London in 1683. 



The above terms are not used at the present time. The 

 bacilli, cocci, and spirilli found in the mouth were supposed 

 by Miller to be intermediate stages in the development of 

 Leptothrix buccalis. Fischer says that the term Leptothrix 

 should only be applied collectively to the mouth bacteria. 

 Miller and others have isolated a large number of species of 

 bacteria from the mouth, but the identity of all these or- 

 ganisms has not been completely established. 



The common saprogenic and zymogenic bacteria are nearly 

 always present in the mouth. The following pathogenic bac- 

 teria are quite often found in the mouth of normal individuals : 

 M. pneumoniae, M. pyogenes var. aureus and var. albus, 

 St. pyogenes, M. sputi septicus, Sar. tetragena. The patho- 

 genic bacteria which occasionally find access to the mouth 

 are as follows : Bact. diphtherias, Bact. mallei, Bact. tubercu- 

 losis, B. tetani, Ps. pyocyanea, and certain of the pathogenic 

 fungi such as Actinomyces var. bovis and var. hominus, 

 O'idium albicans, and various varieties of saccharomycetes. 



Many of the bacteria found in the mouth have the power 

 of producing organic acids. One of the principal acids pro- 

 duced is lactic acid. One of the bacteria which is prominent 

 in the production of this acid is Bact. acidi-lactici. This is 

 the bacterium which causes the souring of milk, and in all 

 probability is introduced into the mouth in milk. 



