white mold. Not infrequently chains of conidia are formed when the culture is submerged in river-water or 4% sugar solution; yet here the spore chains are copiously branched, and the segmentation may even encroach far upon the threads (Gasperini, Lachner-Sandoval). Also some authors describe the occurrence of spore-like formations in the interior of the threads, but we have never certainly seen it. According to Lachner-Sandoval, this is only a fragmentation of the contents of the threads, which must not be interpreted as spore-formation even if it can be demonstrated that such fragments of threads cicatrize at the ends and later grow out again. They are not stained by the T. B. method, but always by Gram's method.1

Key to Some of the More Important Varieties of the Genus Actinomyces.

(A) Pathogenic varieties, with clubbed swellings of the ends of the threads in the animal body. Upon artificial nutrient media the formation of clubs is rare; conidia are sometimes produced in cultures, sometimes not.

(a) No growth below 22°, no growth on potato, no air mycelium, formation of clubs in artificial cultures very limited. Pathogenic for rabbits. Actinomyces Hofmanni. (Gruber.) Gasperini. Page 447. (b) Grow below 22° and upon potato; formations of clubs in cultures scarcely ever observed.

1. Agar cultures, yellowish-orange, knobby, sometimes with air mycelium. Gelatin slowly liquefied. Typical club-formation in the body. Cause of the typical ray-fungus disease in cattle and man. Actinomyces bovis. Gasp. Page 440.

2. Agar growth, dry, granular, scanty. Pathogenic for cattle. Clubs have not been demonstrated in the animal. Actinomyces farcinicus. Gasp. Page 447.

3. Agar culture, a luxuriant, wrinkled, orange-yellow layer, with

1 For the limitations and naming of this genus, see Lachner-Sandoval, Ueber Strahlenpilze, Bonn, 1898; Sauvageau and Radais (A. P. VI, 242, Sur de genre Oospora); and our discussion on page 127. Regarding the species, the following articles are also important: Almquist (Z. H. VIII, 189, 1890), Gasperini (Annales de Micrographie, Bd. II, 449, 1890), and Annal. dell'Istit. d'Igiene di Roma, II, 1892, 166 (C. B. xv, 684). Rossi Doria (Annal dell'Ist. d'Ig. de Roma, Bd. 1892, 399). See also Berestnew (Z. H. XXIX, 94).

2 While we ourselves naturally appreciate that this key is not satisfactory, our information does not allow us as yet to prepare a better

one.

air hyphe. Pathogenic for rabbits. Typical clubs formed in the animail Actinomyces asteroides. Gasp Page 449.

4. Agar growth whitish-red. Conidia are formed.

Beautiful clubs

in the animal. Actinomyces maduræ. Lachner. Page 452. B Non-pathogenic varieties:

1. Growth colless, nutrient medium brown. chromogenes. Gasp. Page 452.

Actinomyces

2. Growth colorless, nutrient medium colorless. Act. chromogenes. Gasp. 3 alba L. and N. Page 455.

3. Growth colorless, nutrient medium colored violet. Act. violaceus. Gasp. Page 456.

4. For varieties with other colors, see Gasperini's Act. carneus, albido-flavus, citreus, etc., pages 451-456.

Actinomyces bovis. Harz.

(Plate 65.)

Synonyms.-Actinomyces bovis Harz, Act. bovis sulphureus Gasp., Nocardia Actinomyces de Toni e Trevisan, Streptothrix Actinomyces Rossi Doria, Oospora bovis Sauv. et Radais.

Common Names.-Ray fungi, Actinomyces.

Literature.-Israel (Virchow's Archiv, Bd. 74, 15; and 78, 421); Boström (Ziegler's Beiträge, Bd. IX, 1). "Actinomykosis" in Eulenburg's Realencyclopædie, Bd. I, 1-94, by Birch-Hirschfeld. Grill (C. B. XVIII, 1-1).

Microscopic Appearance.-In the body of men and animals the organism forms sand-like masses, 0.2 to 0.6 or even as large as 1.2 mm. in diameter, of a gray, yellow, red, sometimes also green color, and when young, of a soft, and when older of a tougher consistency. The masses are made up of a ball of threads, the threads being radially arranged at the periphery and provided with characteristic, club-like formations, which are to be considered as derived from the gelatinous membranes of the threads (Boström). The threads terminate in the clubs, either free or with slight bud-like enlargements (Fig. 20, a, b). The threads show true branching, are thin (0.4-0.6), partly without division, partly apparently composed of longer and shorter fragments. The surrounding "membrane" is very delicate. In the interior of the colonies, there are usually found between the threads, cocci-like formations, which originate from fre

quent fragmentation of the contents of the long threads, and later may be outside of the empty membranes (Fig. 20, c). These are not endospores! Older clubs become notched and cut, so that structures like an asparagus head may occur (Fig. 20, a). Often branched threads reach far beyond the zone with the clubs (Fig. 20, d). Sometimes clubs are entirely absent. Many actinomyces masses are dead when expelled in pus.

In cultures the branching mycelium is easily obtained (65, Ix); the clubs are found only in the deepest layers of the nutrient medium.

Staining Properties.-The threads, but not the clubs, are best stained by Gram's method; afterward the clubs may be stained red with saffranin and diffusely staining carmine. According to Berestnew (Z. H. XXIX, 94), young actinomyces clubs stain by Ziehl's method, sometimes also by Gram's method.

Relation to Oxygen.-Grows aerobically and anaerobically, but better aerobically (Boström). The growth is limited.

Chromogenesis.-The production of pigment is exceedingly variable; from white to various shades of yellow, orange, rusty, and brown appear to occur upon the various nutrient media; the darker tones at least predominate upon serum media, the brighter ones on gelatin.

Gelatin Plate.-(a) Natural size: After six days the colonies have a very irregular outline, are yellowishgray, shining, sometimes fairly elevated above the surface of the gelatin, sometimes growing deeply into it (65, IV).

(b) Magnified sixty times: Dark yellowish-gray, homogeneously shaded colonies, sometimes presenting more or less distinct concentric rings. The peripheral zone is dark and beset with fine, curly hair (65, vII).

Gelatin Stab.-Surface growth at first is whitish-yellow, flatly elevated, faintly shining, rather tough; later the growth sinks into the gelatin with the limited liquefaction, leaving an air-space above. In the stab at first there are small yellowish-white clumps, which later have bristly outgrowths (65, III).

Agar Plate. Macroscopically and microscopically

e. Part of a cluster with fragmentation in the interior. Fig. 20-Formation of clubs in Actinomyces bovis. Harz (after Boström). (a, b, and c are highly magnified-about 1000 to 2000 times; d, e, and f, slightly magnified.)

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scarcely distinguishable from those in gelatin plates, except that the colors are fainter.

Agar Streak.-At first delicate, like dewdrops; then there slowly forms (after six to ten days) a whitish to whitish-yellow growth with an abruptly scalloped border, faintly lustrous and fairly elevated. This gradually comes to resemble a growth of Mycobacterium lacticola with its elevated paddings and ridges. After a very long time (thirty days) the growth gradually becomes dry, sinks in, and the color changes from white to yellow or brown. The culture appears to grow deeper into the nutrient medium, and often becomes surrounded by a more delicate zone, but in our cultures, in distinction to Boström's, no air hypha and no downy appearance was formed. The water of condensation remained clear.

Serum Streak Culture (after Boström).—At first the colonies are like dewdrops, which first become a little broader and thicker; then, extending out from some places, a whitish, velvety, dry covering is obtained. While the surface of the colony which is turned toward the serum gradually becomes colored from yellowish-orange to brickred, as do the older, puffed portions of the growth,-a delicate border of transparent bristling hairs is formed about the growth, in which later there form anew little buttons and puffs, which are first whitish and then change to yellowish or reddish.

Bouillon Culture. The bouillon remains clear; at the bottom ball-like masses form, which are broken up with difficulty by shaking. Colonies upon the surface were never observed by us and rarely by Afanassiew. Microscopically the balls consist of threads with radially arranged fibers. Even in old bouillon cultures we could see no clubs.

Milk Culture.-Unchanged after eight days.

Potato Culture. Slightly knobby, yellowish-white layer, closely attached to the potato, strictly limited to the streak. Often there occur distinct white, or yellow, and, according to Boström, also red spots (65, VIII).

Special Nutrient Media.-According to Boström, the fungus also grows in non-albuminous nutrient media, and even in sterilized water, as it does in bouillon. In an