MICROORGANISMS OF THE DIGESTIVE TRACT 499 



monia. The influenza bacillus and Bad. diphtheria are also occasion- 

 ally found in the throats of healthy persons as well as of those suffering 

 from the diseases to which they give rise. 



Microorganisms of the Stomach. — The microbic flora of the 

 healthy stomach consists almost exclusively of organisms swallowed. 

 The gastric juice restrains bacterial multiplication and kills a large 

 majority of the bacteria which enter the stomach. In diseased con- 

 ditions the absence or reduced concentration of the hydrochloric acid 

 may permit the multiphcation of yeasts, of large lactic-acid bacilli 

 (Boas-Oppler bacilli), of encapsulated cocci (Sarcina ventriculi), or 

 even of flagellate protozoa, such as Lamhlia and Trichomonas. 



Microorganisms of Intestine. — The duodenum receives from the 

 healthy stomach relatively few living bacteria. The secretions of 

 the liver, pancreas and of the duodenal wall are very free from bacteria 

 and they tend to flush out the duodenum. In health this portion of 

 the intestine is quite free* from living bacteria in the intervals when 

 food is absent and it contains relatively few bacteria during digestion. 

 Among the living microorganisms most frequently found here are Gram- 

 positive cocci which fail to liquefy gelatin. B. coli is uncommon. In 

 spite of the negative results of culture work upon duodenal juice, it is 

 always possible to see with the microscope abundant bacterial cells in 

 it. These are probably dead. 



From the upper end of the jejunum to the ileocecal valve, the 

 number of bacteria in the small intestine progressively increases. In 

 the intervals when food is absent, even these portions of the small 

 intestine tend to free themselves from bacteria, in part, probably, 

 because they are continually flushed out by the intestinal secretion, 

 but probably in part also, as has been maintained by Kohlbrugge,t 

 because of a -definite bactericidal property of the' intestinal mucous 

 membrane. ' However this may be, it is certain that living organisms 

 of the B. coli group and various streptococci are commonly found in 

 intestinal contents taken from the jejunum or Ueum at operation or at 

 autopsy and that these organisms are quite numerous in the material 

 discharged from the lower end of the small intestine in cases of ileo- 

 cecal fistula. % The relative abundance of the different kinds of bacteria 



• MacNeal and Chace, Arch. Int. Med., 1913, XII, 178. 



t Kohlbrugge, Centrabl. f. Bakt. Abt. I, 1901, XXIX, 571; ibid., 1901, XXX, lo; ihid., 

 1901, XXX, 70. ' 



t Macfayden, Nencki und Sieber, Arch. f. Exp. Path, und Pharm., 1891, XXXIII, 311. 



