102 SAPROPHYTISM, PARASITISM AND PATHOGENISM 
patients, using material from tlie dento-gingival spaces. In a series 
of patients presenting well-defined clinical manifestations of pyorrhea, 
hemolytic streptococci were isolated from 31.1 per cent of the cases. 
Also, hemolytic streptococci were found between the teeth and gums in 
3 out of a total of 15 cases of gingivitis. The relatively small number 
of cases of pyorrhea from which hemolytic streptococci were isolated 
suggests that these organisms are not necessarily the primary etiological 
factor in this condition. The removal of bacteria from the teeth and 
gums cannot 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 transported 
from the mouth to the stomach during the processes of mastication and 
deglutition. The oral flora is most numerous before eating and almost 
absent immediately after eating a hearty meal. Tubercle bacilli are 
swallowed thus and many of them eventually appear in the feces. 
Stomach.— The acidity of the stomach during gastric digestion, 
by virtue of the free hydrochloric acid of the gastric juice, is a potent 
factor in the destruction of bacteria which reach the stomach both 
from the mouth and the respiratory tract. Mineral acids are much 
more powerful germicides than organic acids. Davis^ has examined 
the feces of more than 50 individuals without finding hemolytic 
streptococci, and Reudiger^ was unable to find them even in the feces 
of scarlet fever patients. Davis believes that the normal gastric juice, 
which kills these organisms in litro in five minutes, is the important 
protective factor. The normal stomach, therefore, is quite free from 
inflammations or irritations attributable to the activity of bacteria. 
Many bacteria, however, run the gauntlet of the stomach successfully, 
especially when the stomach is empty (when the concentration of 
hydrochloric acid is very low) and pass into the intestinal tract, where 
the conditions are much more favorable for their growth. The passage 
of bacteria through the stomach probably takes place either very early 
in gastric digestion, when the hydrochloric acid is not at its "digestive 
concentration" (about 0.2 per^cent), or after gastric digestion has 
ceased. When water or other fluids are drunk, which do not call forth 
an excretion of gastric juice, bacteria doubtless pass through the 
stomach unharmed, and it is probable that organisms included mechan- 
ically within food particles may occasionally escape the action of the 
normal gastric acidity. 
Certain aciduric bacteria,^ and even yeasts which are tolerant of 
acid may be found occasionally in the normal stomach, but rarely 
or never pathogenic bacteria. Abnormally, particularly when the 
hydrochloric acid is deficient, many bacteria are found in the stomach 
contents. Obstruction of the pylorus tends to increase the number 
of bacteria in the stomach by promoting stasis of food. This con- 
dition is particularly common in carcinoma of the pylorus. The 
1 Jour. Infec. Dis., 1920, 26, 171. 2 ihja., 1906, 3, 755. 
3 Kendall: Jour. Med. Res., 1910, 25, 117. 
