674 



NON-PATHOGENIC BACILLI. 



gelatin stick cultures liquefaction occurs at first in funnel form along the 

 line of inoculation, and rapidly progresses until the gelatin is entirely lique- 

 fied; numerous grayish flocculi are seen in the liquefied gelatin, and a deli- 

 cate, grayish-white, wrinkled layer forms upon the surface; an abundant 

 flocculent deposit collects at the bottom of the tube. Upon the surface of 

 agar a dirty-white layer is developed. Upon potato a thick, wrinkled, 

 white layer, extending over the entire surface, is quickly developed ; this 

 penetrates the substance of the potato and is extremely viscid, stringing out 

 into long threads when touched with the platinum needle. Spores are 

 formed in the bacilli cultivated upon potato. Upon blood serum a white 

 layer is developed and liquefaction of the medium occurs. Grows in bouil- 

 lon containing one part in two hundred of hydrochloric acid (Vignal). In 

 milk causes coagulation of the casein, which is subsequently dissolved and 

 floats upon the surface as a slimy layer (Fliigge). 



368. BACILLUS MESENTERICUS FUSCUS (Flugge). 



Found in the air, in hay dust, upon potato, and in water a common and 

 widely distributed species. 



Morphology. Slender and short bacilli, often in pairs or in chains of four. 



Biological Characters. An aerobic, liquefying, actively motile bacillus. 

 Forms small, shining spores which are irregularly distributed in the rods. 

 Grows at the room temperature. Upon gelatin plates forms spherical, 

 whitish colonies, which under a low power are seen to have a well-defined 

 contour; later these are surrounded by delicate offshoots, have a yellowish- 

 brown color and a finely granular surface ; liquefaction of the gelatin 

 quickly occurs. In gelatin stick cultures a whitish cloudiness is first seen 

 along the line of puncture, and at the same time liquefaction commences 

 near the surface in funnel form; this extends to the walls of the tube in 

 from four to six days, and the liquefied gelatin contains numerous grayish- 

 white flocculi. Upon potato, at the end of twenty-four hours, a smooth, 

 yellowish layer is developed ; the surface of this soon becomes wrinkled and 

 brown in color ; the growth is comparatively thin and does not penetrate 

 deeply into the potato, as is the case with Bacillus mesentericus vulgatus ; 

 it extends rapidly over the entire surface. 



369. BACILLUS MEGATHERIUM (De Bary). 



First found upon the leaves of boiled 

 cabbage. 



Morphology. Bacilli with round 

 ends, about 2.5 ft, thick and three to four 

 times as long as broad ; often somewhat 

 curved ; forms chains containing as many 

 as ten elements; the protoplasm of the 

 cells is granular; involution forms are 

 common. 



Biological Characters. An aerobic, 

 liquefying, motile bacillus. The move- 

 ments are peculiar, being slow and 

 amoeboid in character. Forms long- 

 oval spores which are nearly as long as 

 the cells containing them, but not so 

 broad. Grows best at the room tempe- 

 rature also in the incubating oven. 

 Upon gelatinplates forms whitish, puiic- 

 tiform colonies, which under the micro- 

 scope are yellowish and irregular in 

 form. The superficial colonies are some- 

 times kidney-shaped or crescentic ; they 

 cause the gelatin to be slowly liquefied. In gelatin stick cultures lique- 



FIG. 225. Bacillus megatherium; a, chain 

 of bacilli (x 250); 6, bacilli (x COO); c-f 

 shows the development of (spores ; h-m 

 shows the germination of spores; p, bacilli 

 stained with solution of iodine. (De Bary.) 



