CHAPTER XXIV. 



BACILLUS COLI COMMTJNIS (OR COLON BACILLUS OF 

 ESCHERICIl). 



THIS organism was first described by Emmerich 

 (1885), who obtained it from the blood, various organs, 

 and intestinal discharges of cholera patients at Naples. 

 It was afterward found by Escherich (1886) in the 

 feces of healthy milk-fed infants and by Weisser in 

 the alvine discharges of healthy men. It has since 

 been demonstrated to be a normal inhabitant of the 

 intestines of man and of many of the lower animals. 



Morphology. The size and shape of the bacillus coli 

 varies considerably in its morphology according to the 

 sources and the culture media from which it is obtained. 

 The typical form is that of short rods with rounded 

 ends, from 0.4/z to 0.7/* in diameter by I/JL to 3// in 

 length; but sometimes the rods are so short as to be 

 almost spherical, resembling micrococci in appearance, 

 and, again, they are somewhat oval in form or are seen 

 as threads of 6^ or more in length. The various 

 forms may often be associated in the same culture (Fig. 

 58). The bacilli may occur as single cells or as 

 pairs joined end-to-end, rarely as short chains. In 

 unfavorable culture media in stained preparations they 

 may present unstained spaces (vacuoles) and more in- 

 tensely stained portions at the extremities, closely 

 resembling spores, but these are due, according to 



