THE COLON, TYPHOID AND DYSENTEftY BACILLI 339 



causes fatal peritonitis. Subcutaneous injection may also cause 

 death but frequently results in a local abscess. 



The cultures of B. coli on ordinary media are practically free 

 from soluble poisons, but there is some evidence that soluble 

 poisons may be produced by this organism under special condi- 

 tions.^ The bacterial cell substance is poisonous. 



As it grows in the intestine the colon bacillus is a harmless 

 commensal but with a distinct tendency to invade the living 

 tissue and become pathogenic whenever the normal resistance is 

 lowered. The bacilli doubtless pass through the intestinal wall 

 in very small numbers during absorption of the food and are de- 

 stroyed in the normal body fluids and tissues in a few hours. In 

 intestinal disturbances the invasive properties and the virulence 

 are increased. In many other regions of the body the colon bacil- 

 lus gives rise to inflammation, often purulent in character. It 

 is a common cause of cystitis and pyehtis, and is an important 

 agent in the causation of peritonitis following perforation of the 

 intestine. Generalized infection with B. coli is rather uncommoii. 

 The bacilli frequently enter the blood stream from the intestine 

 during the death agony, and are often present in the heart's blood 

 at autopsy, especially if this is delayed. 



The detection of B. coli in any material is ordinarily regarded 

 as evidence of fecal contamination. Examinations of drinking 

 water and of shell liquor from oysters are, perhaps, the most fre- 

 quent applications of this principle. Fermentation tubes of 

 dextrose broth are inoculated with measured quantities of the 

 liquid to be tested, o.oi c.c, o.i c.c. and i c.c. Those cultures in 

 which gas is produced are plated on litmus lactose media and the 

 typical colonies transplanted to gelatin, milk, fermentation tubes 

 of dextrose broth and agar slants, and for final identification the 

 agglutination test with a known colon-immune serum may be 

 employed. 



Bacillus (Lactis) Aerogenes. — Escherich described this organ- 

 ism in 1886 as distinct from B. coli. It is non-motile, is usually 

 ' ' See Vaughan and Novy: Cellular Toxins, Phila., 1902, p. 220. 



