28 INFECTIONS OF THE DIGESTIVE TRACT 



can divert from the anaerobes, and it is easy to check 

 the growth of anaerobes which are not facultative by 

 passing oxygen with some freedom through the fluid 

 medium, no matter how many aerobes are present. 



A study lately made by Willimsky * on the adaptation 

 of aerobic bacteria to anaerobic conditions shows that 

 aerobic bacteria like the spirillum of cholera, B. alkali- 

 genes, B. fluorescens non liquefaciens, are able to adapt 

 themselves to an atmosphere in which there remains 

 only a minimal trace of oxygen and that this adapta- 

 tion is the more efficient the more slowly the oxygen is 

 withdrawn, sudden withdrawal of oxygen greatly slowing 

 the multiplication of the organisms. The multiplication 

 of organisms was found, however, to be much less rapid 

 where oxygen had been thus withdrawn than where it 

 is present. When an absolutely anaerobic condition was 

 brought about, the organisms died, and their destruction 

 was the more rapid, the more abrupt the withdrawal of 

 oxygen. 



The symbiosis of aerobes and anaerobes is a biological 

 phenomenon of much consequence in determining the 

 distribution of anaerobic bacterial processes in the diges- 

 tive tract. Without such symbiotic action the develop- 

 ment of strict anaerobes would be confined to those parts 

 of the digestive tract into which oxygen rarely passes, 

 and then only in small amounts. The large intestine 

 is seldom visited by free oxygen, but it is probably 

 usual in man for the small intestine to contain a little 



1 "Ueber des Verhalten der aeroben Keime gegeniiber der ab- 

 soluten Sauerstoffentziehung," Archiv f. Hyg., liv, p. 375, 1905. 



