446 MEMOIES OF THE NATIO]S"AL ACADEMY OF SCIENCES. 



Sur/ar gelatin in deep stab. — Fair growth, exteudiug all along the liue of inoculation as a narrow 

 cylinder; no gas is produced. 



Knsolic acid. — The color is deepened. 



Indid production. — A good reaction; does not form nitrites. 



Relation to temperature. — Grows well at 35^ to 30° C 



Bacillus arboiesceiis ( Franklaud.) 

 Varieties « auil h. 



Isolated from the water of the Delaware Eiver. A medinmsized, slender, nornnotilc bacillus, 

 occurring often in pairs and indistinctly segmented threads; no spore formation observed. 



Colonies in gelatin. — About the third day the surface colonies may be several millimeters in 

 diameter, and consist of yellowish collections of tlocculi lying in depressions containing liqaetied 

 gelatin, each surrounded by a translucent, almost invisible, hazy zone. The deep colonies are 

 rounded, hazy, translucent spots. Under a low power the surface colonies are seen to consist 

 about their centers of irregular, broken, semitranslucent, yellow, granular masses, while toward 

 the periphery they form thin translucent zones, marked here and there with delicate lines, and 

 lying on the surface of the nouliquefled gelatin. These thin, peripheral expansions in turn are 

 continuous with anastomosing networks or plesitses of numerously branching, thin, delicate, 

 translucent processes of varying widths, which extend for some distance on the surface of the 

 gelatin. The surface colonies are subject to some variation in appearance, dei^eudent on the 

 gelatin used, but the characteristic thing is the anastomosing peripheral zone, and it will usually 

 be seen more or less well developed; the deep colonies also vary in their appearance. The 

 typical deep colony, under a low power, when very yonug and almost invisible to the imked eye, 

 may be seen to consist of a translucent, axial trunk, breaking up at both ends into more or less 

 numerous branches, which, in turn, break \\\> into smaller ones. By the third day the colony has 

 a bushy appearance (see PI. I, fig. !t), consisting of a yellow, semitranslucent, gnarled looking, 

 central axis, which expands at either pole into a rapidly branching and rebranching tree-like 

 structure. The colony thus seems, in typical cases, to be composed of two symmetrical halves, 

 the outlines of the growth being in general rounded or spherical and well defined. A rather slow 

 liquefaction of the gelatin, which has been permeated by the growtb, occurs. In some cases the 

 characteristic bushy appearance of the deep colonies may be absent, and they may be seen under 

 a low power to be yellow, refracting, granular masses, sometimes in pairs, and may be provided 

 with numerous short, irregular, hair like processes, extending into the gelatin. 



A probable variety of this bacillus has been isolated liom the same source, the colonies of 

 which seem to liquefy more rapidly and difter from the above in their apjiearance. They form 

 liquefactions several millimeters in diameter, containing yellow flocculent material, and show 

 fine delicate lines or threads radiating toward the periphery. The deeper colonies consist of 

 yellowish ijoints, surrounded by wide, well-defined, hazy zones, through which radiate delicate 

 lines. The larger colonies under the low power show filaments and bundles of filaments running 

 in a radial direction in the liquefied gelatin, sometimes twisted and contorted, and becoming 

 smaller toward the periphery. In some cases indications of the formation of the cliaracteristic 

 anastomosing peripheral zone of the colony first described may be seen. In addition to these 

 elements granular clumps and masses of a yellow or brown color will be seen, esi)ecially about the 

 centers. The deep colonies under the low i)ower have a yellow granular central nucleus, from 

 which filaments extend into a wide, faintly granular zone with a circular outline and a faint fringe 

 at the periphery. These filaments in some cases form delicate threads running to the ijeriphery 

 of the surrounding zone, giving the radiating appearance seen by the naked eye. In other cases 

 these radiating lines may be absent, as in fig. 9, PI. I. It would seem that this zone is really 

 formed by an extensive branching of the filamentous outgrowths from the central nucleus, together 

 with the liquefaction or semiliquefaction of the gelatin threads permeated by them. 



Gelatin .stab. — Liquefaction in cup shape or deep saucer form, with haziness along the line of 

 inoculation (tig. G). The liquefaction extends to the tube wall, and slowly downward, the How 

 becoming level. The liquefied gelatin is clouded, and yellow in color, with a yellow sediment at 



