530 PATHOGENIC AEROBIC BACILLI 
Obtained by Emmerich (1885) from the blood, various organs, and 
the alvine discharges of cholera patients at Naples; by Weisser 
(1886) from normal and abnormal human feces, from the air, and 
from putrefying infusions; by Escherich (1886) from the fasces of 
healthy children ; since shown to be commonly present in the alvine 
discharges of healthy men, and probably of many of the lower ani- 
mals. Found by the writer in the blood and various organs of yellow- 
fever cadavers, in Havana (1888 and 1889). 
Numerous varieties have been cultivated by different bacteriolo- 
gists, which vary in pathogenic power and to some extent in their 
growth in various culture media; but the differences described are 
not sufficiently characteristic or constant to justify us in considering 
them as distinct species. 
Morphology.—Differs considerably in its morphology as obtained 
from different sources and in various culture media. The typical 
form is that of short rods with rounded ends, from two to three pu in 
length and 0.4 to 0.6 4 broad; but under certain cir- 
cumstances the length does not exceed the breadth— 
e% 
Rie! , about 0.5 u—and it might be mistaken for a micrococ- 
Vays? © cus; again the prevailing form in a culture is a short 
® oval ; filaments of five “or more in length are often 
Fie. 144.—Ba- observed in cultures, associated with short rods or oval 
wrong nw ton cells. The bacilli are frequently united in pairs. The 
(scherich.) presence of spores has not been demonstrated. In un- 
favorable culture media the bacilli, in stained prepara- 
tions, may present unstained places, which are supposed by Escherich 
to be due to degenerative changes in the protoplasm. Under certain 
circumstances some of the rods in a pure culture have been observed 
by Escherich to present spherical, unstained portions at one or both 
extremities, which closely resemble spores, but which he was not able 
to stain by the methods usually employed for staining spores, and 
which he isinclined toregard as “‘ involution forms.” 
This bacillus stains readily with the aniline colors usually em- 
ployed by bacteriologists, but quickly parts with its color when 
treated with iodine solution—Gram’s method—or with diluted al- 
cohol. 
Biological Characters.—An aérobic and facultative anaérobic, 
non-liquefying bacillus. Sometimes exhibits independent move- 
ments, which are not very active. One rod of a pair, in a hanging- 
drop culture, may advance slowly with a to-and-fro movement, 
while the other follows as if attached to it by an invisible band 
(Escherich), The writer’s personal observations lead him to believe 
that, as a rule, this bacillus does not exhibit independent movements. 
Does not form spores. Grows in various culture media at the room 
