BACTERIOLOGICAL EXAMINATION OF MATERIAL 217 



may be accidental and temporary invaders, members of pathogenic 

 groups which, either because of the reduced virulence of the strains 

 or the increased resistance of the individual are not capable under 

 the circumstances of causing their specific infection. 



It is such conditions which may lead to many erroneous etiological 

 conclusions and which render the investigation of the causation 

 of diseases in the mouth, intestines and other locations extremely 

 difficult. It is perhaps best to discuss this subject from the point 

 of view of the individual locations studied. 



Bacteria in the Normal Mouth and Pharynx. The mouth and 

 pharynx are habitually the habitat of numerous bacteria. Saliva 

 itself is not a good culture medium, and, indeed, may, according 

 to some investigators, show very slight inhibitory or even bacteri- 

 cidal powers. But these, at best, are not very potent, and the saliva 

 thus is a basis for a fluid medium which furnishes water as a solvent 

 and a reaction suitable for a great many different bacteria. 



Sloughing epithelium, decayed teeth and gums, food particles, 

 etc., furnish suitable nutrition. Catarrhal inflammation which is 

 rarely entirely absent to some degree or in some place in the adult 

 human being, favors the lodgment of bacteria upon the membranes 

 and reduces the resistance of the tissues. 



In spite of these facts, it is surprising that the frequent accidental 

 injury of the gums and oral and pharyngeal mucous membranes 

 so rarely leads to serious infection, and ends so readily. This is 

 a fact which has not as yet been adequately explained. 



Staphylococci can almost always be isolated from the mouth. They 

 are usually of the Albus variety, but not infrequently staphylococcus 

 Aureus also can be found. 



Of the streptococci the Viridans is almost always present. The 

 isolation of a "viridans" from inflammatory processes of the mouth 

 and throat, therefore, has very little true significance, unless it is 

 isolated from a closed process, such as a tooth abscess, or unless other 

 strong corroborative evidence can be adduced. The Hemolyticus 

 variety is less frequently found in the normal mouth, but may be 

 present without causing disease. However, the isolation of a hemoly- 

 ticus from an inflamed tonsil or pharynx is much more likely to 

 mean that there is an etiological relationship, and it is of course well 

 known that many of the severe inflammations in this location are 

 of hemolyticus origin. 



In examinations made many years ago by the writer, 30 per cent 



