CHAPTER XX. 



Some of the Pathogenic Organisms Encountered in the Mouth Cavity in 

 Health and Disease Micrococcus Lanceolatus, Micrococcus Tetragenous, 

 Bacterium Influenzas, Bacillus Tuberculosis, etc. 



USUALLY in the course of certain diseases, and from time 

 to time in health, pathogenic bacteria are to be found in 

 the mouth. In the latter instance the organisms, while 

 often fully pathogenic, as shown by tests on animals, do 

 apparently no harm to their hosts, with whom they live 

 in a commensal relationship. Moreover, they are often not 

 regularly and persistently present at times they may 

 disappear permanently, at other times they may be recur- 

 rent, with varying intervals, for longer and shorter periods. 

 The "pneumococcus," as it is called; the Micrococcus 

 tetragenous; the influenza bacillus, the Bacillus diphtherias, 

 and the ordinary pyogenic streptococci may be cited as 

 occasional guests in the normal mouth cavity. In diphtheria, 

 tonsillitis, influenza and tuberculosis, the specific organisms 

 of these diseases may usually be detected either in the ordi- 

 nary saliva or in the sputum brought up from the deeper 

 respiratory tract. 



To familiarize one's self with these organisms and the 

 customary technique for their isolation one may proceed as 

 follows : 



Obtain from a tuberculous patient a sample of fresh 



sputum that of the morning is preferable. Spread it in 



a thin layer upon a black glass plate and select one of the 



small, white, cheesy masses or dense mucous clumps scat- 



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