524 PATHOGENIC AEROBIC BACILLI 



bottom, leaving- the bouillon entirely clear. In agar-agar tubes, a veil- 

 like stripe develops along the line of puncture, and a grayish-yellow, moist 

 layer, with irregular outlines upon the surface. After some weeks this 

 acquires a brown color. No growth occurs upon potato. No development 

 occurs in the incubating oven at 37 C. 



Pathogenesis. Trout became infected and died through direct infection, 

 subcutaneous or intramuscular inoculations, or through the addition of cul- 

 tures to the* water in which they were kept, or by placing infected fish in the 

 same tank with healthy ones. 



170. GAS-FORMING AEROBIC BACILLUS OF LASER. 



Obtained by Laser (1892) from a piece of liver and lung from a calf which 

 died of an infectious disease. 



Morphology. " Short bacilli." 



Biological Characters. An aerobic and facultative anaerobic, non- 

 liquefying, motile, gas-producing bacillus. Stains by Gram's method. 

 Spore formation not observed. In gelatin stick cultures development oc- 

 curs on the surface in the form of a button-like mass, and along the line of 

 puncture colonies are formed which may be separate below. The colonies 

 in gelatin and agar plates are not characteristic. Upon agar, at 37 C. a 

 slimy, moist, shining layer is developed which covers the entire surface. In 

 stick cultures in gelatin or agar containing glucose an abundant develop- 

 ment occurs, attended with an evolution of gas. In bouillon, in the incubat- 

 ing oven, a uniform cloudiness of the culture medium is seen at the end of 

 twenty-four hours, and the bacilli gradually sink to the bottom of the tube. 

 Upon potato in the incubating oven, a shining, white layer is developed 

 over the entire surface ; on potato kept at the room temperature a thick, 

 grayish-yellow layer in the middle, which gradually becomes more decidedly 

 yellow, while the potato around this growth has at first a violet shimmer, 

 and later an intense violet color. 



Pathogenesis. The limited number of experiments made on mice, rab- 

 bits, and guinea-pigs resulted in the death of some of the animals, while 

 others recovered. (This appears to be a bacillus of the colon group, which 

 differs but little from Bacillus coli communis. G. M. S.) 



171. BACILLUS OF BECK. 



Synonym. Der Bacillus der Brustseuche beim Kaninchen. 



Obtained by Beck (1892) from rabbits which died of an infectious malady 

 in the Institut fiir Infectionskrankheiten, in Berlin. 



Morphology. Very small and slender bacilli, about twice as long and 

 twice as thick as the influenza bacillus ; somewhat pointed at the extremities ; 

 show a tendency to grow out into filaments. 



Biological Characters. An aerobic (strict) non-liquefying, non-motile 

 bacillus. Spore formation not observed. Grows at the room- temperature 

 and more vigorously at 38 C. Does not stain by Gram's method. Thermal 

 death point, 50 C. (five minutes). Resists desiccation, at the room tempera- 

 ture, for seventeen days, at 37 C. for three days. 



On gelatin plates, at the end of forty-eight hours, small, finely granular, 

 glass-like colonies are developed ; older colonies have a pale-brown appear 

 ance. In gelatin stick cultures a granular growth of a white color is seen 

 along the line of puncture. Upon agar, at 37 C., an abundant development 

 occurs in twenty -four hours. The line of puncture seen from above is gray- 

 ish-white, by transmitted light bluish and porcelain-like with a brownish 

 tint. On agar plates the colonies have a yellowish-gray appearance ; the 

 margin of the finely granular colonies is sharply defined. In agar cultures 

 several days old the colonies are sticky and may be picked up as a compact 

 mass, or drawn out into threads. In bouillon, at 37 C., there is a slight 



