flat, primarily non-characteristic, smeary growth on potato, which later forms large, parallel folds. The resisting spores withstand a short baking process.

The Bac. gummosus Ritsert (C. B. XI, 730), obtained from gelatinous infusion of digitalis, seems to be related. See also Happ (C. B. XIV, 175). According to both authors, this organism is only able to elaborate this slimy material from cane-sugar and not from grape- or milk-sugar. Besides, there originate mannite, grape-sugar, lactic acid, butyric acid, and carbonic acid. The carcinoma bacillus of Scheurlen (C. B. III, 397) has also been shown to belong to this group, but has nothing to do with carcinoma.

Bacillus geniculatus (Duclaux). L. and N.

Tyrothrix geniculata Duclaux. The gelatin plates macroscopically resemble Bac. vulgatus. When magnified 60 times, they present an interesting exhibition. The colonies at first appear upon the gelatin with delicate scalloping, like typhoid; with advancing liquefaction the scallops are replaced by curls, which in irregularity may compare with those of anthrax; still later, the circle of locks falls away and the compact colony floats in the shallow liquefied area, surrounded by irregular disintegrating masses. Also in the growth upon potato and in other properties it resembles the Bac. vulgatus. We have seen nothing of the branches in gelatin as described by Winkler.

Bacillus mesentericus. (Flügge.) Lehm. and

Synonym.

-

Neum.

(Plate 43.)

Bacillus mesentericus fuscus Flügge.

(Flügge, 3d Edit., p. 199.)

Microscopic Appearance.-Slender rods with rounded ends, 0.8-2.4 long, 0.7-0.9 thick, having a tendency to form roundish spores.

Motility, staining properties, and conditions of life are like those in the case of the Bac. vulgatus.

Gelatin Plate.

(a) Natural size: Minute, roundish, grayish-white colonies, which very soon sink into the gelatin. The zone of liquefaction is flat, gray, cloudy. The colonies resemble very much those of subtilis (43, x).

(b) Magnified fifty times. Superficial: In the earliest stages they resemble those of typhoid, as do those of the Bac. vulgatus (43, XI). (See also 16, VIII.) With the onset

of liquefaction the transparent peripheral zone becomes delicately granular, at the periphery appears a row of fine hairs, and the entire colony assumes the character of a liquefying subtilis colony. The center is usually grayish-brown and opaque (43, IX). Deep: Grayish-yellow, irregular; about the edge are curling, hairy outgrowths.

Gelatin Stab.-The colony after twelve to twenty-four hours sinks into a saucer-shaped depression. The liquefaction first assumes a funnel form and later progresses in a cylindric manner. The contents of the funnel are cloudy, with a whitish-gray film upon the surface (43, 1). Agar Plate.

(a) Natural size: Roundish, gray, thin, veil-like growths, transparent, with the original whiter colony in the center (43, v).

(b) Magnified fifty times: The original colony lying beneath the superficial colony appears yellowish-brown, moderately or very crummy, with an even border or with curling outgrowth. When the colony reaches the surface, it forms a delicately punctated, transparent, irregular growth of a gray to yellowish color (43, VII).

Agar Streak.-Wavy, moistly shining, yellowishbrown, in many places gray and transparent. Water of condensation cloudy, with yellowish precipitate and a pellicle upon the surface (43, 11).

Bouillon. Moderately cloudy, pellicle on the surface. Potato. At first the growth is moderately elevated, grayish-yellow, moistly shining, slimy (43, 1). Later it is transformed into a meshwork of irregularly anastomosing wrinkles, which are much elevated, of a yellowish-gray color, and possess a dull luster (43, IV).

Chemical Activities.-See preliminary remarks on page 306. It forms little indol and abundant H2S.

Distribution, Practical Importance, Etc.-Like Bac. vulgatus.

Bacillus mesentericus ruber. Globig (Z. H. iii, 322).

Slender bacilli, 1 to 3.2 μ long, 0.4 μ thick, sometimes forming quite long threads. Not motile, stain by Gram's method, no spores. The gelatin plate exhibits quite variable forms. At first all the colonies present an appearance like typhoid; later some colonies retain the

same, others form thick, moist, white growths, still others liquefy and form pellicles, and yet others resemble subtilis colonies. Upon the gelatin stab is formed a growth like typhoid, which still, after a longer time, slowly sinks in, with the form of a funnel. Potato cultures at first are like Bact. coli; later the cultures acquire a rose-color, which finally is transformed into reddish-brown. Agar stab culture is delicate, whitish-gray, transparent, moistly shining; later a netted film forms upon the surface. Bouillon becomes faintly cloudy, with a thin pellicle upon the surface. Milk is not coagulated, reaction feebly alkaline. HS and gas are not produced.

Bacillus aterrimus. (Biel.) Lehm. and Neum.

A very striking, aerobic, motile, sporulating bacillus, possessing all the peculiarities given on page 306, and producing black pigment. The gelatin plate cultures appear to resemble Bac. subtilis and vulgatus. Gelatin stab cultures present funnel-shaped liquefaction without coloration. Upon potatoes at first grayish-blue, then brownish-black, wrinkled, moist pellicles are formed, the potato being black throughout. Agar cultures become brown with yellowish-brown films. The organism is not pathogenic. Compare Biel (C. B. L. II, 137) and Lunt (1. c., 572) regarding B. mesentericus niger. Gorini's closely related Bac. lactis niger (C. B. xx, 94) we obtained from Král in 1895 and studied. It no more showed any chromogenesis, and grew as a flat deposit upon potato, resembling the Bact. coli. Spontaneous motion could not be seen. It is questionable whether the insufficiently described Bac. melanosporus Eidam of Schröter belongs here.

Bacillus liodermos. (Flügge.) Lehm. and Neum. Bacillus mesentericus liodermos Flügge.

This bacillus, described by Flügge as short and very actively motile, we have not certainly encountered during recent years. The gelatin growths in plates and in the stab are like Bac. vulgatus. The potato culture forms a smooth, shining, yellowish-white, syrupy growth, which only after several days becomes a little wrinkled and cloudy. The Bacillus mucosus Zimmermann (II, p. 8), from slimy water, appears to have some relationship.

Bacillus gangrænæ pulpæ.

Arkövy.

Caries fungus of

Synonyms.-Bacillus fuscans Miller? Galippe and Vignal, Caries fungus of Jung.

Literature.-Arkövy (C. B. XXIII, 917).

According to the investigations of Dr. Zierler, made in the Würzburg hygienic institute, which deviate somewhat

1

from those of Arkövy in some points, 1 the following are the characteristics (compare Zierler, C. B. xxvi, 417):

Microscopically.-Stout rods, 4 long, about 0.8-1.0 μ thick, often united in chains. Actively motile. Staining of flagella has not been successful. Upon all nutrient media large, oval spores soon form, which are difficult to stain. Germination of the spores is equatorial, often oblique to the axis of the spore (Hirai). Grows luxuriantly on all nutrient media, best at 37°. Gelatin plate: Similar to subtilis, rapid liquefaction. Gelatin stab: "After two or three days saucer-shaped liquefaction, which becomes cylindric. Upon the surface a very tough, wrinkled film, which usually remains connected by a fine string with the stab canal in the solid gelatin. The liquefied mass gradually becomes colored smoky brown. After two to four days fine, horizontal branches are seen throughout the entire length of the stab canal. Anaerobic gelatin stab: Without liquefaction and pellicle formation, the surface gradually becomes depressed. The branches in the stab are longer and more delicate. Agar plates: Thick plates exhibit superficial colonies something like subtilis (39, VI and VII); thin plates present dense, scalloped, concentrically striped, white growths, which, when magnified fifty times, appear opaque, and from the rather sharp border bunches of threads project outward. Deep colonies are compact and often whetstone-shaped. Agar stab: The growth rapidly spreads over the surface of the agar and is whitish, dense, with a dull luster; soon it becomes a little rough from the formation of small depressions and elevations. Potato: On first day, a delicate, membranous, moist, spreading growth; after three to four days the same becomes finely wrinkled and dirty red, and the neighborhood of the growth is stained dirty violet. Bouillon is very cloudy, with a dense, wrinkled surface pellicle. In a few days, with the formation of a rather crummy precipitate and brownish discoloration, the culture becomes clear. Neither H,S nor indol is formed. Milk is coagulated after two or three days. In grape-sugar bouillon there is

1 Nothing was seen of the pleomorphism of Arkövy, and the "cocci forms represented by Arkövy are often spores (C. B. XXIII; Plate XVIII, 10).

abundant formation of gas (principally CO,) and moderate formation of acid.

Arkövy always found the fungus in gangrenous teeth, and frequently in saliva and in gangrenous wounds (decubitus).

Zierler, like Arkövy, never failed to find the organism in gangrene of the pulp (24 cases examined), those in which the characteristic gangrenous odor was present. Not infrequently pure cultures were obtained, and, what appears especially remarkable, scarcely ever a culture of any other sporulating bacillus.

Zierler can not bring forward direct proof of the significance of the organism as the cause of gangrene. Arkövy has inoculated sound, broached human teeth with the bacillus and thus produced gangrene.

Further Sporulating Aerobic Varieties.

Here are included the thermophilic varieties which were spoken of from the biologic side in the general part. (See p. 44.) For the characteristics of the individual varieties we must refer to the original literature there cited, since they have only been partly named and are without great practical interest. They appear to be concerned in the spontaneous heating of hay, manure, etc., also in the hitherto puzzling bubbling fermentation." Laxa has described an organism which belongs here (C. B. L. IV, 362), and Poupé (C. B. L. iv, 484) another thermophilic, jelly-forming organism.

Introduction to the Special Description 1 of the Bac. tetani, Bac. Chauvei, and Bac. œdematis maligni. The three varieties have in common:

1. In pure cultures upon the usual nutrient media. (agar, gelatin, potato) they are more or less perfectly anaerobic; on the contrary, they also grow very well

1 In the following, free use is made of v. Hibler's critical "Beiträge zur Kenntnis der durch anaërobe Spaltpilze erzeugten Infektionserkrankungen des Menschen, etc." Preliminary communication (C. B. XXV, 1899, 513, etc.). The detailed work has not yet appeared (June,