174 MICROBES, 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. 
Sternberg, surgeon of the United States army, 
1880, writes: “When I was occupied in the micro- 
Fig. 19.—Vibrio rugula (Warming) in different stages of development: 0, ¢, f, indi- 
viduals with vibratile cilia (flagellum); f’, 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,and a variety of minute 
spherical forms and of rods, difficult to classify except 
under the generic names of Micrococcit and Bacteria. 
Another organism which I have often found in healthy 
human saliva is a species of Sarcina, perhaps identical 
with S. ventriculi.” 
But the organism most commonly found in the 
human mouth, which attracts attention from its large 
