MEMOlllS OF THE NATIONAL ACADEMY OF SCIENCES. 



4Q[ 



Fig. 27. 



cliiiiips, more closely g;itliered to.uetlier about the center may lie sometimes observed. At the 

 iiiiirgiii tliere is a fringe of short ladiatiiig tibrils. Tlie deep colonies arc rounded, dark, aud 

 granular, and may have a greenisli shimmer. They soon become suirounded by a 

 zone of li(iuefaction, and break tlirougii the gelatin to form (-olonics similar to those 

 desciibed above. When they are Just beginning to liiiuefy they are sul)ject to some 

 variation in their ajijiearance. 



Gelatin stah. — Li(juefactiou rapidly extends to the wall of tlie tube at the surface, 

 and also all along the inoculation line, in a form varying from that of a funnel to that 

 of a champagne ghiss. (See fig. 27.) The li(iuefled gelatin is ch)uded, aud when the 

 liquefaction is well advanced along the line of inoculation a thick, whitish, tlocculent 

 mass is seen at the bottom. On the surface there is a delicate pellicle, and in com- 

 pletely li(iuetied cultures beneath this a greenisli tint may be ob.served. The reaction 

 of the liquefied gelatin is alkaline. 



Aciil gelatin. — Crows less vigorously. 



Af/ar ulant. — Semitransluceut, shining, grayish, rather thin stripe, with scalloped 

 margins. In older culture becomes a dirty brown color, while the agar acquires a 

 marked brown-green tint. 



Bouillon. — Clouded. A broken, imperfect pellicle forms on the surface and the 

 bouillon acquires a brown green tint. 



Potato. — Variable, tliick, widely spreading, dense growth, somewhat rough or granular on the 

 surface; the color varies from cream-gray to piukisli. 



Litmus milk. — Coagulated and decolorized; cloiuly serum, contaiuing flocculi; reaction is 

 neutral or slightly acid. 



tSui/ar (/elatin in derp stah. — Fair growth with some gas production. 



Bosolic acid. — Color deepened. 



Indol production. — Marked reaction; does not produce nitrites. 



Relation to temperature. — Grows at the temperature of the room au<l at .35° to '500 C. 



Eemarks. — This bacillus and its varieties, owing to the rapid and widely spreading liquefactiou 



of the colonies, interfere moi-e thau any of the other liquetiers with the satisfactory study of the 



"water" plates. 



Bacillus centrifugans. 



(Variety /i. ) 



A polar, flagellated bacillus, which is probably to be considered as a varietj' of the bacillus, 

 has been isolated from the same source. With the exce{)tiou of the diflerences noted below, the 

 description given above ajiplies equally well to this organism, ])oint for point. 



Colonies in (jelatin. — To the naked eye the colonies are hardly to be distinguished from tliose 

 of the preceding, but under a low power they are seen to have no dark, granular clumps in their 

 interiors, but instead may show some dark streaks about their centers, while their margins do not 

 have the radiating fringe so well defined, and it may be absent. 



These differences, although trivial when analyzed for description, are well marked to a prac- 

 ticed eye. The deep colonies, when examined with a low power, are seen to be rounded, dark, 

 granular, and sometimes have a greenish shimmer. The margins are rather uneven and not very 

 sharply defined, in some cases broken. They soon become surrounded by a granular zone, become 

 disintegrated, and form rounded liquefactions. 



Gelatin stab. — The manner of liquefactiou is very similar to that of the preceding, but with 

 the following differences in other respects. The liquefied gelatin is moi'e homogeneously clouded 

 and has a different ajipearance, while the most marked characteristic of this variety is the absence 

 of the thick, tlocculeut, whitish deposit at the bottom of the liquefactiou. 



Bacillus fimbriatus. 



Isolated from the water of the Delaware River. A medium sized, motile bacillus, with rather 

 blunt ends, generally rathei- short, but occurring in long forms and sometimes in chains. It has 

 several Hagella; no spore formation observed. 



C<donies in gelatin. — About the second day the surface colonies are rounded in outline, yellowish 

 white in color, sunken in the gelatin, and in some cases surrounded by a cloudy li(pietied zone. 



