724 DISTRIBUTION AND HABITAT OF THE BACTERIA. 



ratory mucous 

 membrane. 



In the 

 stomach. 



tion need not be immediately preceded by the reception 

 of the infective agent. Possibly this is the meaning of 

 the observation made by Loeffler on the presence of the 

 diphtheritic bacilli in the secretions of the mouth of a 

 healthy child (see p. 287). 



Ontherespi- Various bacteria (e.g., Micrococcus tetragenus) are 

 also found in the laryngeal mucus, and in that of the 

 trachea and bronchi ; these have been carried in by the 

 respired air, and have in part multiplied to a considerable 

 extent in the mucus. 



Enormous numbers of bacteria are also met with in 

 the intestinal tract. Numerous forms are found even 

 in the contents of the stomach. It has been erroneously 

 assumed that the acid contents of the stomach kill most 

 forms of bacteria ; this is, however, not the case. 

 Feeble action Experiments which have been made by Mac Fadyan 

 ] ? uice 6 gastlic in the autllor ' s laboratory have shown that even the 

 strongly acid gastric juice of the dog can kill only 

 cholera and anthrax bacilli with anything like con- 

 stancy, that, however, most other bacteria are not so 

 susceptible to the action of the gastric juice, and can 

 pass in a living state through the stomach even when 

 conditions are as favourable as possible for an energetic 

 action of the gastric juice ; among bacteria which 

 behave in this way may be mentioned micrococcus 

 tetragenus, staphylococcus aureus, bacillus cuni- 

 culicida, &c. 



Hence there is for the most part only a temporary 

 hindrance to development in the stomach, and vegeta- 

 tive forms such as spores reach the small intestine in a 

 living condition in large numbers. There they find a 

 good opportunity for development so long as the reaction 

 of the chyme remains neutral or faintly alkaline ; it is 

 true that this multiplication appears to be limited 

 chiefly to certain definite forms of bacteria, so that in 

 spite of the multiplicity of forms and varieties which 

 strikes one at first, there are some which evidently find 

 in the intestinal contents a particularly favourable soil 

 for multiplication, and occur there almost constantly. 

 These prevailing varieties seem to vary according to the 



In the 

 intestine 



Some prevail 

 ing varieties. 



