INFECTIONS OF THE DIGESTIVE TRACT 23 



AEROBIC AND ANAEROBIC CONDITIONS IN THE 

 DIGESTIVE TRACT 



There are many conditions which influence the char- 

 acter and extent of bacterial decompositions in the ali- 

 mentary tract. The chemical character of the food 

 (quite aside from the bacteria it may contain) , the 

 solubility of the food in the digestive juices, the volume 

 and composition of these digestive juices, all affect in 

 important ways the ultimate fate of the food in its 

 relation to microorganic decomposition. Some phases 

 of these influences will be discussed in these pages in 

 connection with special problems, although it must 

 be owned that our knowledge of them is far from being 

 full, owing partly to the great difficulties of experi- 

 mental investigation. Intimately intermingled with 

 these factors of food and secretory activity is the influ- 

 ence of aerobic and anaerobic conditions in the digestive 

 tract upon the nature of the bacterial activities that 

 occur there. 



Pasteur, with his sharp insight into biological phe- 

 nomena, was first in recognizing the ability of certain 

 microorganisms (including a butyric acid producer, 

 yeast plants, aspergillus, and some mucors) to live in the 

 absence of oxygen and thereby first to distinguish be- 

 tween aerobic and anaerobic life. He embodied his views 

 in a famous epigram, the validity of which has been much 

 discussed " Fermentation is life without oxygen." 

 This statement, although too sweeping and exclusive, 

 has in it a large element of truth and has a special 



