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 faeces, from the air, and 

 from putrefying infusions ; by Escherich (1886) from the faeces 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 >w in 



length and 0.4 to 0.6 /^ broad ; but under certain cir- 



^ ^ cumstances the length does not exceed the breadth 

 ff WJ/ J ^ about 0.5 fj. and it might be mistaken for a micrococ- 

 cus ; again the prevailing form in a culture is a short 



oval ; filaments of five /* or more in length are often 

 FIG. 144. Ba- observed in cultures, associated with short rods or oval 

 emus coii com- u The bacilli are frequently united in pairs. The 



munis. X 1 000. _ 



(Escherich.) 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 is inclined to regard 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 aerobic and facultative anaerobic, 

 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 



