102 SAPROPHYTISM, PARASITISM, AND PATHOGENISM 



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. 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 prob- 

 ably 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 gastric juice, bacteria 

 doubtless pass through the stomach unharmed, and it is probable 

 that organisms included mechanically within food particles may 

 occasionally escape the action of the gastric acidity. 



Certain aciduric bacteria 1 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 

 Oppler-Boas bacillus, sometimes called B. geniculatus, one of the 

 aciduric bacteria, is so frequently found in this pathological condition 

 it was at one time supposed to be an accessory factor; it is now known 

 to have no relationship to gastric carcinoma. B. geniculatus is also 

 found very commonly in cases of achlorhydria. Sarcina ventriculi 

 is also found in similar conditions. 



The gastric acidity will destroy the toxins of B. diphtherise and 

 B. tetani; the toxin of B. botulinus is not inactivated by the gastric 

 juice. The toxins of the paratyphoid group of bacteria also appear 

 to be resistant to gastric digestion. 



1 Kendall, Jour. Med. Research, 1910, N. S. f xviii, 153. 



