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tively immunized animals possesses active bactericidal substances. In the place last referred to is also found an extensive review of the literature.

Bacterium of Brick-pock (Backsteinblättern).
Lorenz (C. B. xi, 672).

A disease of swine,-evidently to be considered as a form of swine erysipelas,—which almost always runs a favorable course, has been described by Lorenz as brick-pock, and he has ascribed it to an organism which, upon subcutaneous inoculation, stands midway, as to virulence for swine, between mouse septicemia and swine erysipelas. After inoculation with it, swine become immune to swine erysipelas. Rabbits, on the contrary, in a very interesting manner are much more susceptible to brick-pock than to swine erysipelas. They always succumb to brick-pock infection, but may be immunized with swine erysipelas against brick-pock. Lorenz likewise holds that swine erysipelas, mouse septicemia, and brick-pock are produced by forms of one organism, even if the transformation of one form into the other has not been entirely successful.

2. Bacillus F. Cohn, emend. Hüppe.

Straight rods, often growing into threads, often of considerable thickness, rarely less than 0.6, usually more than 0.8 . They form endospores.

Key to the Recognition of the More Important
Varieties of the Genus Bacillus. 2

I. AEROBIC VARIETIES, thriving only scantily anaerobically. The pathogenic ones never form spores in the animal body, but only in cultures with oxygen admitted (compare also p. 310). Almost all in cultures grow into long threads with central spores.

1 Regarding our insufficient knowledge of this genus, consult the statements upon page 306 and in the discussion of the anaerobes. Numerous new aerobic varieties are described by Burchard (A. K. II, 1).

It

2 The genus Tyrothrix Duclaux is included in the bacilli. designates primarily varieties originating from milk and cheese, which form spores and grow into long threads. Two species are described below: Bac. tenuis and Bac. geniculatus. The most remarkable statements of W. Winkler regarding extraordinary biologic and morphologic variability, especially in the Bact. tenuis (C. B. L. 1, 657), could not be confirmed either by ourselves (see first edition) or by

(A) Stab culture in gelatin with projecting branches :

1. Branches distinct, usually only in the upper part of the stab. Agar plate colonies, when magnified 60 times, have beautiful regular curls. Agar streak culture without branches, wide, white with "silvery vesicles." Never motile. Pathogenic for animals. Bac, anthracis Cohn and Koch (p. 307).

2. Branches delicate, extending along the entire length of the stab. When magnified 60 times, the colonies in the agar plate exhibit irregular outgrowths in the form of roots or the mycelium of molds. Agar streak culture has long, delicate, parallel transverse branches. Sluggishly motile. Not pathogenic for animals. Bac. mycoides Flügge

(p. 316).

(B) Stab culture in gelatin without projecting branches; motility dependent upon peritrichous flagella:

1. Potato growth at first moist and flat, later (about eight days) with a distinctly mealy sprinkling. Bac. subtilis Cohn (p. 317).

2. Potato growth moderately elevated, not characteristic, resembling Bact. coli. Bac. oxalaticus Zopf, butyricus Hüppe, megatherium De Bary (pp. 321, 322, and 323).

3. Potato culture luxuriant, moist, intensely yellow. Agar moist, mustard yellow. Later resembles vulgatus. Bac. luteus L. and N. 1 4. Potato is not characteristic during the first days; later, there forms a distinct, wrinkled elevation.

(a) The folds are padded, like coils of intestine. Bac. vulgatus (Flügge) Migula (p. 323).

Growth yellowish.

(b) The folds are low, reticulated. mesentericus (Flügge) Lehm. and Neum. (p. 326).

Bac.

(c) Growth moist, wrinkled, besides the potato is deep black. Bac. aterrimus Lehm. and Neum. (p. 328).

(d) Growth rose-colored, a little wrinkled, gelatin smoky brown. Compare also Bac. mesentericus ruber. Bac. gangrænæ pulpæ Arkövy (L. and N.) (p. 328).

5. The potato growth is delicate, syrupy, clear. Bac. liodermos (Flügge) Lehm. and Neum. (p. 328).

II. ANAEROBIC VARIETIES (of which, certainly, partially aerobic forms exist). Only exceptionally form long threads. Staining by Gram's method rarely well developed (the Bac. tetani stains well). Spontaneous motion dependent upon peritrichous flagella is rarely lacking. The spore is usually located at the end (paraplectrum form) or at the middle, usually with some bulging (clostridium form). In most varieties both forms of sporulation occur. The recognition of the individual varieties, which is often very difficult, and even impossible, may be rendered somewhat easier by means of the following scheme:

(4) Pathogenic Varieties.

Wittlin (C. B L. II, 475); and since then, so far as we know, it has not been upheld.

1 For more details regarding this organism, compare Bacillus luteus sporogenes Wood Smith and Baker (B. C. L. IV, p. 788).

1. In a deep cutaneous pocket in animals no local symptoms are produced, but only or preponderantly nervous symptoms.1

(a) Produces tetanus. Bac, tetani Nicolaier (p. 332).
(3) Causes symptoms of botulism: disturbances of the innerva-
tion of the pupils and accommodation, aphonia, paresis in the
region of the tongue and pharynx, disturbances of the salivary
and mucous secretions, etc. Bac. botulinus v. Ermengem (p.
337).

2. When introduced into a deep cutaneous pocket in animals, it causes local bloody, often emphysematous edema. The organism spreads in the body, especially in the edema. Guinea-pigs are especially susceptible. 2

(a) Motile.

(a) In the edema growing into long, jointed threads, usually not present in the bile. Very pathogenic for rabbits. Brain nutrient media darkened. Not stained by Gram's method. Bac, cedematis maligni (Koch) Flügge (p. 341). (3) No long threads in edema; usually only pairs. Usually slightly pathogenic for rabbits and mice. Always found in the bile. Brain nutrient media not darkened. Usually stained by Gram's method. Bac. Chauvoi of French authors (p. 339). (b) Not motile. Disease picture similar to symptomatic anthrax, but there is a tendency to grow into long threads. Bac. phlegmonis emphysematosæ E. Fränkel (p. 344).

3. Only known as injurious to bees. Bac. alvei Chesire and Cheyne (p. 345).

(B) Zymogenic Varieties.—

A large group which has not yet been sufficiently cleared up. Compare page 345, etc.; also especially page 348. Here belong many forms producing butyric acid.

Introductory Remarks to the Special Description of the Aerobic Varieties Here Given.

(Common Characteristics.)

All of the varieties described in what follows,-Bac. anthracis, mycoides, subtilis, megatherium, butyricus, vulgatus, mesentericus, aterrimus, liodermos,-which are very closely related to each other, have the following biologic properties in common, which may be given here for all of them:

1 Non-pathogenic cultures cannot always be diagnosed with certainty from the morphologic and biologic properties.

2 Compare also the Bac. sporogenes (Klein) L. and N. (p. 346), which occupies a place midway between malignant edema and symptomatic anthrax; also the pseudoedema bacilli (p. 343).

1. Gelatin is liquefied.

2. Milk is alkaline or very feebly acid in reaction, is coagulated, and later the coagulum is dissolved.

3. All form little acid from grape-sugar (see Table I, at end of the book, for quantitative statements) and no gas. From milk-sugar there is formed little or no acid.

4. No indol is formed. The production of HS is variable, never abundant.

5. All are stained by Gram's method.

The equipment with flagella appears also in this group to be valuable for the diagnosis of species only with great precautions. When present, they are peritrichous.

Bacillus anthracis. F. Cohn and Koch.

(Plates 34, 35, and 36.)

Ordinary Names.-Anthrax bacillus, Bactéridie du charbon.

Microscopic Appearance.-In the animal body it occurs as large vigorous rods, 3-10 μ long, 1-1.2 μ thick, which are often arranged in longer or shorter chains (36, 1). The ends in fresh specimens are a little projecting (rounded); after drying and staining, they appear squarecut or slightly concave. To demonstrate the capsules, which are always well developed in the animal body, fluid blood-serum, and brain-agar mixture,-the directions given in the technical appendix are to be followed. According to Kern, capsules may be demonstrated in old cultures upon most variable nutrient media. 1

In artificial nutrient media the bacilli grow into long threads, placed parallel or somewhat twisted and entangled (36, 11), which either produce spores (see below) or perish in the formation of bizarre involution forms (36, v). The threads, even when unstained, give indications of their being composed of separate bacilli (36, VI). This is especially distinct after staining.

1 Noetzel has also demonstrated capsules in undoubted "cadaver bacilli," and this points out how unsafe it is to allow the diagnosis of anthrax to rest upon the demonstration of capsules, which is often very much overestimated by veterinarians. (C. B. XIX, 498.)

Motility. Always is absent. To this no exception is known.

Staining Properties.-Stains with all anilin dyes and by Gram's method.

Relation to Oxygen.-Grows best when oxygen is admitted. When oxygen is excluded, it grows poorly and without liquefaction. There is no growth in CO,.

Intensity of Growth.-Grows rapidly, especially at 37°. Lower limit of growth at 14° (Kitasato).

Gelatin Plate.-(a) Natural size. Superficial colony: Whitish, round; after three or four days, deeply sunken. Also, upon longer standing the liquefaction only extends slowly. In the middle of the abrupt crater there lies a white, crumbly, poorly defined mass, the remainder of the contents of the liquefied area being rather clear, but the outermost peripheral zone is somewhat turbid again (35, v ). (b) Magnified seventy times: The colonies when three days old appear distinctly darker than on agar. Near the center grayish-yellow, toward the edge more distinctly transparent. At the periphery the formation of locks is clearly seen, but toward the center they become very dense and indistinct (36, vi). The liquefaction is recognized as a grayish reflex. Later an irregularly outlined ball, devoid of distinct locks, floats in the liquefied medium.

Gelatin Stab.-Along the stab there forms a thick white thread, from which, as a rule, only in the upper part (34, II), more rarely throughout the entire length, long (34, 1) or short (34, III), bristly, distinct outgrowths extend outward. Sometimes the growth of hairs fails entirely (34, IV). Also the direction of the lateral outgrowths varies; many times they are tangled together (34, v). After twelve to twenty hours there begins a slowly progressing liquefaction, with limited depression of the surface of the gelatin. The liquefaction at first is cup-shaped, later cylindric. The content of the funnel. is sometimes diffusely cloudy with white crumby flocculi; at other times the flocculi settle down, leaving a clear liquid gelatin above. No pellicle is ever formed.

Agar Plate.-(a) Natural size. Superficial colonies: Small, white, with a play of yellow, moistly shining, a

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