IN SUSCEPTIBLE ANIMALS. 457 



83. BACILLUS OF LASER. 



Obtained by Laser (1892) from mice which succumbed to an epidemic dis- 

 ease in Frankel's laboratory at Konigsberg. 



In its characters this bacillus closely resembles the bacillus of swine 

 plague (No. 65), and is perhaps identical with it. 



Morphology. A small bacillus, with rounded ends, about twice as long 

 as broad. Has flagella both at the extremities and sides. 



Stains by the usual aniline colors and also by Gram's method. 



Biological Characters. An aerobic and facultative anaerobic, non- 

 liquefying, actively motile bacillus. Spore formation not observed. Grows 

 either in the incubating oven or at the room temperature. Thermal death - 

 point 65 to 70 C. ten minutes' exposure. Upon gelatin plates, at the end 

 of two days, the deep colonies are spherical, finely granular, and brownish 

 in color; the superficial are transparent, finely granular, and leaf -like. 

 In gelatin stick cultures growth occurs along the entire line of puncture as 

 well as upon the surface. At the end of three days a considerable evolution 

 of gas is usually observed. In agar an abundant development is seen at the 

 end of twenty-four hours in the incubating oven; upon the surface a gray- 

 ish-white, shining layer with dentate margins is formed along the track of 

 the needle. In bouillon, at 37 C., development is abundant and rapid; a 

 thin film is formed on the surface at the end of the second day. Upon potato 

 a brownish layer is formed at the end of twenty-four hours. In milk an 

 acid reaction is produced. 



Pathogenesis. Pathogenic for field mice, guinea-pigs, rabbits, and 

 pigeons. The bacillus is found in the blood and various organs of infected 

 mice. The spleen is found to be greatly enlarged. 



84. BACILLUS TYPHI MURIUM (Loffler). 



Obtained by Loftier (1889) from mice which died in his laboratory from 

 an epidemic disease due to this bacillus. 



Morphology. Short bacilli, resembling the bacillus of diphtheria in 

 pigeons, and varying considerably in dimensions like the bacillus of 

 typhoid fever ; grows put into flexible filaments. 



Stains with the aniline colors best with Loffler's solution of methylene 

 blue. 



Biological Characters. An aerobic and facultative anaerobic, non- 

 liquefying, motile bacillus. Spore formation not determined. Has flagella 

 around the periphery of the cells, like those of the typhoid bacillus, and ex- 

 hibits similar active movements. In gelatin stick cultures, at the room 

 temperature, growth occurs upon the surface, at the end of forty-eight hours, 

 in the form of a flat, grayish-white, round, semi-transparent mass the size of 

 a pin's head ; later the surface colony increases in extent and has more or 

 less irregular margins. In gelatin plate cultures the deep colonies are at 

 first round, slightly granular, transparent, and grayish ; later they are of a 

 yellowish-brown color and decidedly granular. The superficial colonies are 

 very granular and marked by delicate lines similar to colonies of the 

 typhoid bacillus. Upon agar a grayish- white layer is developed which is 

 not at all characteristic. Upon potato a rather thin, whitish layer is formed, 

 and around this the potato acquires a dirty bluish-gray color. In milk an 

 abundant development occurs, and a decidedly acid reaction is produced 

 without causing any perceptible change in the appearance of the fluid. 



Pathogenesis. Pathogenic for white mice, which die in from one to two 

 weeks after infection ; also to field mice, which succumb to subcutaneous in- 

 jections of a pure culture, and also, in from eight to twelve days, when fed 

 upon potato cultures or bread moistened with a small quantity of a bouillon 

 culture. Loftier believes that this bacillus may be used for the destruction 

 of field mice in grain fields, inasmuch as they invariably die after ingesting 

 food which has been contaminated with it, and also from eating the bodies 

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