58 TRANSFORMATION OF THE INTESTINAL FLORA 



other carbohydrates used would disappear from the enteric tract before 

 the colon is reached and hence would not offer the favorable pabulum to 

 the aciduric organisms. 



To establish the validity of the above assumption, at least in so far 

 as the availability of the carbohydrates in the lower intestine is con- 

 cerned, the following experiments were conducted in addition to the 

 examination of fecal specimens for reducing substances. A number of 

 rats which had been receiving one or another of the carbohydrates, lac- 

 tose, dextrin, maltose, sucrose and glucose, as well as control rats sub- 

 sisting on the basic diet alone, were killed and careful examinations made 

 of the contents of the caecum and colon for the presence of reducing 

 substances and the corresponding predominant bacterial types. 



The contents of both the caecum and colon of each rat, in amounts 

 ranging from one half to one gram, were placed in large test tubes 

 containing twenty cubic centimeters of water and broken glass and 

 shaken until a fairly homogeneous suspension was obtained. The tubes 

 were then heated in a boiling water bath for ten minutes to hasten the 

 extraction of the carbohydrate from the suspended particles. After 

 thorough centrifugation the supernatant fluid was filtered twice. In 



CHART 28 



Curves indicating average percentages of B. bul- 

 garicus and B. acidophilus appearing in fecal 

 specimens from rats fed on a diet con- 

 taining lactose and B. hulgaricus 



too 



Alumher of days a/risr adrni/i/s^rcf/ron of c/itf^. 



2 4 e a lo iz 1^ 



