PARASITIC AND PATHOGENIC BACTERIA 101 



2. Mucous Membranes. The moist surface of mucous membranes 

 makes them excellent culture media for many bacteria which can 

 grow at the temperature of the body. The physiological secretions 

 which bathe these membranes, with the exception of the stomach, 

 are usually without germicidal properties; at best, their antiseptic 

 properties are w r eak. The removal of bacteria from such surfaces 

 is probably for the most part mechanical. The secretion of mucus, 

 which has been shown to enclose bacteria, may be an important factor 

 in their elimination. 



Mouth. The mouth is a most important portal of entry for the 

 great majority of bacteria, both pathogenic and non-pathogenic, 

 which are associated with man. All of the intestinal bacteria, harmful 

 or benign, many of the bacteria which are associated with morbid 

 processes of the respiratory tract, and several which induce specific 

 lesions of the brain and spinal cord enter through this atrium. A 

 great majority of viruses which infect the respiratory tract and the 

 cerebrospirial axis also leave the body through the mouth or nose. 



The normal flora of the mouth is quite varied, 1 including not only 

 bacteria which are ordinarily regarded as harmless, but also organisms 

 which occasionally or frequently incite disease. Thus, from 20 to 40 

 per cent, of healthy individuals living in large cities harbor typical 

 and apparently virulent pneumococci in their mouths; 2 about 2 per 

 cent, of school children harbor typical diphtheria bacilli in their 

 mouths. 3 Rarely, tubercle bacilli have been detected in the mouths 

 of apparently normal individuals. 



It is worthy of note that an occasional abscess in the cervical region 

 may contain spiral organisms; frequently a careful examination will 

 reveal a sinus connecting the abscess with the mouth, perhaps origi- 

 nating at the base of a carious tooth. Dental caries is usually regarded 

 as a bacteriological process. The removal of bacteria from the teeth 

 and gums can not be satisfactorily accomplished by antiseptic mouth 

 washes and the saliva possesses no germicidal properties. Bacteria 

 are removed from the teeth mechanically by friction and are trans- 

 ported from the mouth to the stomach during the processes of mas- 

 tication and deglutition. ' The oral flora is most numerous before 



1 For full literature and descriptions see Miller, Die Mikroorganismen der Mundhohle, 

 Leipzig, 1892, and Goadby, Mycology of the Mouth, 1903. 



2 Recent observations by Cole and his associates indicate that the ordinary "mouth" 

 pneumococci differ in their serological reactions from pneumococci isolated directly 

 from pneumonia lesions. 



3 Moss, Guthrie and Gelien have found a much larger proportion of diphtheria bacillus 

 carriers during a period when diphtheria was epidemic. 



