MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



461 



sharply defined zone uC Hiiuefied gelatin, in which scattered f>ra'i>il''s may he seen. This zone of 

 iiqnetaction, with its sharply defined circular outline, may f;ive the colony tlie aiipearance of being 

 encircled at its periphery by a well-marked line. 



In some cases the area of licjnelaction may become much wider and the colony, lying in a 

 depression containing clear, li(|nefied gelatin, appears, under the low power, lo be sur- 

 rounded by a moie or less well-defined refraction ring. 



The colonies do not increase in size, or very little, and liquefaction is not rajiid. 



Gelatin stah. — Li(iiiefaction in deep saucer form extending to the tube wall 

 and slowly downward (tig. 2r>). After the tube wall has been reached the tlow of 

 the liquefaction becomes a horizontal i)laue, and liquefaction slowly occurs along the 

 line of inoculation. Tlie liquefied gelatin is clouded and there is an abundant whitish 

 Hocculeut deposit in the lower portions. After some time a greenish color may be 

 observed in it. 



Acid geidtin. — (irowth feeble; no liquefaction. 



Agar sJant. — Semitrauslucent grayish stripe, not widely spreading, with irregular, 

 sharply defined margins. The agar acquires a brown greenish tint. 



Bouillon. — Clouded, whitish sediment. It seems probable that a slight jiellicle may 

 form on the surface. The bouillon acquires a slight green tint. 



Foiato. — Brown, viscid, moist, shining, rather widely spreading layer. 



JAtmus mill;. — Coagulated with clouded serum. Clot is firm and of a pink and „ „. 



° ' Fig. 2o. 



Avhite color; reaction is acid. 



tSugar gelatin in deep sfah. — (lood growth of discrete and confluent whitish colonies. Marked 

 gas production ; no liquefaction. 



Rosolic acid. — Color markedly deepened. 



Indol j))odnction. — Marked reaction; does not produce nitrites. 



Relation to temperature. — Does not grow well at 35° to 36^ C; development is very faint at 

 this temperature. 



Bacillus convolutus. 



Isolated from the water of the Schuylkill Eiver. Not common. A large baeillus, generally 

 long, occurring in twisted chains and threads; also singly and in pairs. It seems to have some 

 motility under certain circumstances, but it is ordinarily nonmotile; no spore formation observed; 

 in old cultures the jirotoplasm seemed to be shrunken away from its envelope. 



Colonies in gelatin. — On the second day the surface colonies are rounded, grayish 

 white, wooly looking, translucent, glistening, and somewhat opalescent. They may 

 be 2 mm. or i mm. in diameter. Under a low power they resemble the external aspect 

 of the cei-ebral cortex, being made up of coiled and twisted broad bands, between 

 which slight branching fissures or dark lines are seen. (Pl.I, fig. 2.) These bands 

 seem to be composed of closely packed parallel lying threads. The outline is sharply 

 defined and wavy, corresponding to the external or peripheral "bands." Toward the 

 center the cidony may be darker, where there may be a rounded, dark nucleus. The 

 deep colonies under a low power are rounded, sharply defined, dark, grauular, and 

 sometimes have a greenish shimmer. In the course of a few days the colonies become 

 thicker and denser and sink into the gelatin, which is slowly liquefied. Under the 

 low power they now have a greenish shimmer. 



Gelatin .stab. — Saucer-shaped, slow liquefaction, with only faint growth in the 

 V J line of inoculation. (Fig. 20.) Liquefied gelatiu is densely clouded and thei-e is an 

 pj;j-^ abundant, thick, whitish sediment. The reaction is alkaline. 



Acid gelatin. — Grows sonuMvhat less vigorously, and there is little or no growth 

 along the line of inoculation. The reaction of the liquefied gelatin is alkaline. 



Agar slant. — A grayish, semitrauslucent, not widely spreading stripe, with scalloped margins. 

 The agar acquires a brown-green color. 



Bouillon. — Clouded and thick, flocculent deposit. Au imperfect i)ellicle and wooly shreds 

 may form at the surface; the bouillon acquires a greenish tint. 

 Potato. — Growth varies; it is generally elevated and dense. 



