4(M 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



They are about 1 iiim. to 2 mm. in diameter. Under a low power tliey are rather dense, dark, 



brownish, and granular about their renters. Toward their peripheries they are less dense, 



and haA'e a delicate radiating fringe at the margin. The deep colonies are round, 



granular, and have a gTeenish tint at their centers, where they are denser; their 



ontliues are sharply defined. 



Gelatin stab. — Li(iuefactiun in wineglass form, extending down the line of inocu- 

 lation. (See tig. 28.) The liquetied gelatin is clon<led and there are wliitish flocculent 

 deposits in the lower portions. A delicate, slightly iridescent pellicle forms on the 

 surface. The liqnefaction is slower than in the case of B. centrifugans. In completidy 

 liquefied cultures there is a greenish tint near the surface. 

 Acid (jelatin. — Does not grow well. 



Ai/ar slant. — Smooth, dirty gray, shining stripe, with wavy or scalloped, sharply 

 defined margins; agar acquires a brownish tint. 



Bouillon. — Clouded and whitish sediment. An imperfect delicate pellicle may 

 form on the surface; the bouillon acquires a dark greenish tint. 



I'otato. — Thick grayish or pale brownish, dense, rather rough surface growth, 

 sjireading widely; more or less of a piidcish tint may be seen. The growth on potato 

 is essentially the same as that of B. centrifugans. 



Litmus milk. — Coagulated, decolorized, with separation of cloudy serum witi 

 tlocculi in suspension; there is a l)luish ring on tube wall; the reaction is neutral. 

 Sugar gelatin in deep stab. — Some growth with little or no liquefaction; no gas is produced. 

 Rosolic acid. — Color is deepened. 



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

 Relation to temperature. — Grows at 35° to 3G° C, but seems to grow better at the temperature 



of the room. 



Bacillus coheereus. 



FlQ. 28. 



Isolated from the water of the Schuylkill liiver. Seems to be a common organism. A medium- 

 sized, short, motile bacillus with rounded ends, occurring often in pairs and sometimes in long- 

 forms; it has a i)olar tlagellum; no spore formation observed. 



Colonies in gelatin. — About the fourth or fifth day the surface colonies are round, elevated, 

 grayish, semitransluceut disks, about 1 mm. to 2 mm. in diameter, with sharply defined outlines. 

 Under a low power thej' are finely granular, refracting and slightly yellowish brown in tint toward 

 their centers, where there is a nucleus. The outline is smooth and rounded and sharply defined. 

 The deep colonies under the low power are round or oval granular, brownish, and sharply 

 defined in outline. The surface colonies may increase somewhat in size, becoming thicker, denser, 

 and whiter, with an elevated brownish nodule at their centers. Later they sink into the gelatin 

 and their margins may have a " crimped " appearance. The deep colonies after some days 

 become more brown in color, when examined under a low power, and there may be a slight 

 brownish tint in the gelatin immediately surrounding them, which is not apparent to the naked 

 eye. Sometimes the deep colonies may form morula like aggregations of daughter colonies. 



Gelatin slant. — A more or less wrinkled, viscid-looking, grayish white membrane lining a 

 rather deep furrow in the gelatin, which is very slowly li(jueHed. 



Acid gelatin. — Grows well. 



Agar slant. — An irregular, somewhat elevated, grayish white, semitranslucent, shining growth 

 with irregular margins. 



Bouillon. — Clouded. A coherent, viscid looking, tenacious, much-wrinkled membrane forms 

 on the surface and adheres to the wall of the tube. In older cultures the bouillon seems to 

 become quite clear. 



Potato. — A rather thick, granular-looking, widely spreading growth of the color of the potato. 



Litmus milk. — Decolorized and a viscid coagulation with a layer of smoky, V)luislicolored scrum 

 at the top and a coherent, thick, tough membrane on the surface. The milk acquires a dirty, 

 brownish white color and there is a bluish ring on the tube wall. The casein seems to be slowly 

 •dissolved; the reaction is alkaline. 



Sugar gelatin in deep stab. — Fair growth of disci'ete colonies; no gas production. 



