At the autopsy the small intestine will be found to be injected and containing a flocculent colorless fluid in which comma bacilli are present in great numbers.

Occurrence. In the alvine dejections and in the intestinal contents of cholera patients (Fig. 53). It apparently only rarely invades the circulating blood. Its presence in the vomitus may sometimes be shown. It has been found in the water-supplies during epidemics.

Bacillus of Anthrax' (see also Clinical Bacteriology).Blood-serum.-Irregularly rounded colonies, several mm. in diameter after twenty-four hours in the incubator. The colonies are grayish, finely granular, and have the appearance of being made up of a dense network of delicate fibrillæ. The blood-serum is slowly liquefied.

Morphology. The organism grows in long segmented threads, the segments varying in length, but usually being two or three times as long as broad and having square or slightly concave ends. These segments represent the bacillus, which is among the largest of the bacteria (Fig. 54).

1 Pasteur: Bull. Acad. de Méd., Paris, T. viii., 1879; Koch: F. Cohn's Beitr. z. Biol. d. Pfl., Bd. 2, 1876.

FIG. 54.-Bacillus of anthrax : portion of a colony three days old upon a gelatin plate; X 1000 (Fränkel and Pfeiffer).

Pathogenesis.-Mice, guinea-pigs, and rabbits inoculated subcutaneously die with a general invasion of the blood by

FIG. 55.-Bacillus of anthrax; cover-glass preparation from spleen of a mouse. the organism. Mice are most susceptible to the infection, dying in about twenty-four hours, while guinea-pigs and rabbits survive longer.

In all these animals the most striking lesion is a large soft spleen, and in the guinea-pig also an extensive inflammatory edema of the subcutaneous tissues. On microscopic examination the bacilli will be found in the organs and blood of the heart. If the animal has been dead some time, the number of bacilli present in these situations will be very great, owing to the post-mortem growth. It is characteristic of the bacillus of anthrax in cover-slip preparations from infected tissues that it should have a narrow capsule (Fig. 55)

Pfeiffer).

and show square or slightly concave ends. The capsule is not present in cultures.

Stained by Gram's method. Not motile.

Forms oval spores in the middle of the short segments or rods. The spores may be seen in blood-serum cultures after forty-eight hours in the incubator (Fig. 56).

Gelatin Stab.-Growth along the line of stab, with radiating filaments extending laterally into the gelatin, which is slowly liquefied in funnel form (Fig. 57).

Bouillon.-Growth in the form of cotton-like flakes and filamentous masses. No clouding of the medium. Agar-agar.-Matted network of translucent filaments.

Under a lower magnifying power the growth is seen to be made up of twisted and contorted masses of filaments, giving the appearance of curled hair (Fig. 58).

FIG. 57.-Bacillus of anthrax : gelatin stab-culture seven days old (Günther). Potato.-Grayish-white, rather thick, dry layer, having the appearance of frosted glass.

Occurrence. In malignant pustule, wool-sorter's disease,

FIG. 58.-Colony of bacillus of anthrax, slightly magnified (Flügge). and intestinal anthrax. Found in the blood of animals dead of anthrax. In man the infection is usually localized at

first at the point of inoculation, either on the skin or on the mucous membrane of the air-passages or intestinal tract. Later, a general invasion of the blood may occur and a fatal septicemia result. The organism or its spores may be present in wool or hides, and infection may take place from these.

Bacillus Pyocyaneus (Bacillus of Green Pus).'Colonies on blood-serum grow rapidly, are not especially characteristic in form, and liquefy the medium, imparting to it a dark greenish color.

Morphology.-Small bacilli with rounded ends (Fig. 59).

Decolorized by Gram's method (Welch). Motile, and is provided with a flagellum at one end. Does not form spores.

Gelatin Stab.-Liquefaction in funnel form, with green fluorescence of the upper portions of the medium. The liquefied gelatin is densely clouded, and there may be a viscid pellicle on the surface.

Agar-agar Stab-A green fluorescence in the upper layers of the medium, which later becomes a dark blue-green.

Potato.-Slightly elevated, brownish, viscid layer. The potato in some cases assumes a green color, in others a brown color. In some cultures the potato when touched

1 Gessard: Annales de l'Institut Pasteur, T. 5, 1891.