174 MICEOBES, FERMENTS, AND MOULDS. 



is perfectly sound, at 300,000 a day, and 100,000,000 

 a year. It is evident that these germs, always 

 present, may easily become the source of diseases, of 

 which thrush in the mouth of infants, and of sick and 

 dying adults, is one of the least alarming. 



Steinberg, surgeon of the United States army, 

 1880, writes: "When I was occupied in the micro- 



Fig. 79. Vibrio rugula (Warming) in different stages of development : b, c,f, indi- 

 viduals with vibratile cilia (jlagellum) ; /', ciliated spores. Found in the human 

 mouth and intestines. 



scopic examination of foul river water at 'New Orleans, 

 I used to find in my own mouth almost all the 

 organisms which were present in the putrefying liquid 

 I was examining Bacterium termo, Bacillus subtilis 

 (Fig. 80), Spirillum undulatum,a,nd a variety of minute 

 spherical forms and of rods, difficult to classify except 

 under the generic names of Micrococci and Bacteria. 

 Another organism which I have often found in healthy 

 human saliva is a species of Sarcina, perhaps identical 

 with 8. ventriculi" 



But the organism most commonly found in the 

 human mouth, which attracts attention from its large 



