CHAPTER XXIV. 
BACILLUS COLI COMMUNIS (OR COLON BACILLUS OF 
ESCHERICH). 
Tus 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 0.44 to 0.7 in diameter by ly to 3y 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 ~ 
