CHAPTEE XI 



THE ORGANS AND CAVITIES OF THE BODY AND THEIR 



CONTENTS (contin ned) 



II. THE DIGESTIVE TRACT 

 The Cavity of the Mouth 



Micro-organisms of the mouth and their examination. 

 A number of micro-organisms are found in the mouth, 

 which are derived from the air and are taken into 

 the digestive tract with the food. Their occurrence in the 

 buccal cavity is so constant that in each examination of 

 saliva cocci, bacilli, spirilla, and other fungi are encountered 

 in large numbers. When saliva is freely smeared over the 

 surface of a cover-glass, allowed to dry, fixed in the flame, 

 and stained in a dilute alcoholic solution of an aniline dye, 

 micro-organisms will be found which belong in part to the 

 mouth fungi, the properties of which we know by cultivation, 

 but a large number have not as yet been successfully grown 

 on our nutrient substances. Besides the saliva, the particles 

 of food which remain behind in the mouth, and especially 

 between the teeth, play an important part in the retention 

 of bacteria in this cavity, and to these must also be added 

 changes in the teeth and gams which promote the develop- 

 ment of micro-organisms. The importance of the saliva to 

 the life of the micro-organisms lies in the alkaline reaction 

 which it commonly possesses, since if an acid reaction sets 

 in, its capability of serving as a favourable nutrient 

 medium for microbes becomes diminished ; but in this case, 



