6 INFECTIONS OF THE DIGESTIVE TRACT 



bacteria. Among such bacteria are pyogenic strepto- 

 cocci and staphylococci, the paratyphoid bacilli, typhoid 

 bacilli, the dysentery bacilli, proteus vulgaris, and the 

 spore-bearing anaerobes B. putrificus (Bienstock), 

 B. aerogenes capsulatus, B. botulinus, etc. 



Defensive Action of the Digestive Juices. The normal 

 human organism is provided with more or less efficient 

 (though by no means fully understood) methods of de- 

 fense against these bacterial invaders. The secretion 

 of the gastric juice in normal abundance, after a meal, 

 provides a degree of acidity which acts as an effective 

 check upon the growth'of many non-sporula ting bacteria, 

 and is actually destructive to most varieties at least in 

 a measure. Probably the proteolytic action of the pep- 

 tic ferment and the tryptic enzymes leads to a very 

 quick destruction of any bacteria whose vitality has 

 been lowered by contact with the acid of the gastric 

 juice. If, however, bacteria are administered in very 

 large numbers, there is a chance that a certain proportion 

 of them will run the gauntlet of these defenses and find 

 their way into the lower part of the small intestine and 

 into the colon. This seems especially liable to happen 

 in those cases where the microbes are taken into the 

 empty, non-secreting stomach, or into a stomach with 

 defective motility which secretes little gastric juice with 

 a low content of hydrochloric acid and there are many 

 such stomachs among persons over forty years of age 

 and in fair health. Thus the bacteria (with any spores 

 that may have developed from them or have been in- 

 gested as such) find their way to the region of the colon 



