038 NON-PATHOGENIC BACILLI. 



fringed with short fibres ; later the gelatin acquires a pale-red color, which 

 gradually becomes more intense. In gelatin stick cultures liquefaction is 

 rapid along the entire line of inoculation ; a wrinkled, red film forms upon 

 the surface and grayish- white flocculi accumulate at the bottom of the lique- 

 fied medium. Upon the surface of agar an abundant layer, covering the 

 entire surface, is quickly developed in the incubator ; this usually acquires 

 a brick -red color, but the margins of the layer, or even the entire growth, 

 may remain colorless, especially in cultures kept in the incubating oven. 

 Upon potato development occurs very rapidly along the line of inoculation; 

 this soon acquires the characteristic color. Blood serum is liquefied by this 

 bacillus. Large quantities (twenty cubic centimeti'es) of a pure culture in- 

 jected into a vein or into the peritoneal cavity of a rabbit or guinea-pig 

 cause the death of the animal in from three to twenty hours; at the autopsy 

 an intense gastro-enteritis is, found. 



284. BACILLUS PRODIGIOSUS. 



Synonyms.-' ^Micrococcus prodigiosus; Monas prodigiosa. 



This bacillus has long been known, having attracted attention because of 

 the blood-red stains which it causes upon farinaceous substances, such as 

 boiled potatoes, moist bread, etc. It was described by Ehrenberg under the 

 name of Monas prodigiosa. At times, in certain parts of Europe, it has 

 been exceptionally abundant, and the bloody-looking patches produced by 

 its rapid development upon favorable media have been regarded with ap- 

 prehension, by the superstitious. 



Morphology. Short bacilli with rounded ends, which are sometimes so 

 short as to be scarcely distinguishable from micrococci, but also occur as 

 rod-shaped cells and short filaments ; frequently in pairs and occasionally in 

 chains containing ten or more elements especially in acid media. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing, usually non-motile, chromogenic bacillus. Although usually described 

 as non-motile, this bacillus is said under certain circumstances to be capable 

 of spontaneous movements. According to Schottelius, these are best seen 

 when it is cultivated in strongly diluted liquid media and under urifavoiv 

 able conditions of growth. Forms a red pigment which is soluble in alcohol 

 and ether, but not in water; this is only formed in presence of oxygen; it is 

 changed to a pale-red color by the action of acids, and the deep- red color is 

 restored by ammonia and other strong alkalies. The pigment is not seen in 

 the interior of the bacterial cells, but the chromogenic substance formed by 

 them develops the color outside of the cells, where it is seen in the form of 

 granules. The formation of pigment is influenced not only by the presence 

 of oxygen, which is essential to its production, but also by conditions re- 

 lating to temperature, constitution of the culture medium, etc. By continu- 

 ous cultivation in the incubating oven a non-chromogenic variety may be 

 obtained, and the same result is obtained by continuous cultivation in acid 

 bouillon. But under favorable conditions color production again returns 

 after a few successive transplantations upon potato or nutrient agar, if the cul- 

 tures are kept at the room temperature and freely exposed to the air. Spore 

 formation has not been observed, but this bacillus retains its vitality for a 

 long time in a desiccated condition. Cultures give off a strong odor of tri- 

 methylamm; and in culture media containing sugar, fermentation occurs 

 with production of alcohol and carbon dioxide. This bacillus grows rapidly 

 in the ordinary culture media best at the room temperature or a little 

 above (25 C.). Upon gelatin plates small, white, punctiform colonies are 

 developed below the surface, and upon the surface round, granular colonies 

 which quickly cause liquefaction of the gelatin; saucer-like depressions are 



Eroduced, at the bottom of which the colony is seen as a whitish mass which 

 iter acquires a deep-red color, first appearing at the centre. In gelatin 

 stick cultures liquefaction quickly occurs along the entire line of inoculation 

 and rapidly extends until the medium is completely liquefied ; pigment for- 



