patients, thinking it at first to be the micrococcus of sputum septicæmia; later he believed it to be the cause of pneumonia. Form.-Oval cocci they were at first called, but they are now known to be rod-shaped, being somewhat longer than broad; varying, however, much in size and shape. Usually found in pairs, sometimes in filaments of three and four elements. In the material from the body a capsule surrounds each rod. In the artificial cultures this is not found.

FIG. 70.

Bacillus of pneumonia in blood of rabbit 1000 X. (Fränkel and Pfeiffer.)

Properties. They are without self-movement; do not liquefy gelatine. There are no spores.

Growth.-Grow only at high temperature, 350 C.; are faculThe culture media must be slightly alkaline;

tative anærobic.

the growth is slow.

Colonies on Gelatine Plates.-Since the temperature must be somewhat elevated, the gelatine media need to be thicker than usual (15 per cent. gelatine), in order to keep it solid, and a temperature of 24° C. used. Little round white colonies, somewhat granular in the centre, growing very slowly.

Stab Cultures.-Along the needle-track small separate white granules, one above the other, like a string of beads..

Stroke Culture.-On agar, transparent, almost invisible little drops resembling dew moisture.

Bouillon. They grow better here than in the other media, remaining alive a longer period of time.

Staining.-Takes Gram's method and the other aniline stains very readily. The capsule stained the same way as that of the Friedlander bacillus.

Pathogenesis.-Rabbits and guinea-pigs, if subcutaneously injected, die in the course of a couple of days with septicemia. (0.1 c.cm. of a fresh bouillon culture suffices.)

Autopsy shows greatly enlarged spleen and myriads of bacilli in the blood and viscera, the lungs not especially affected. If injected per trachea, a pneumonia occurs. In man in 90 per cent. of croupous pneumonia they are found and usually only during the existence of the "prune juice” sputum, i. e., the first stage.

FIG. 71.

Micrococcus tetragenus in sputum (tubercle bacillus also).

They have also been found in pleuritis, peritonitis, pericarditis, meningitis, and endocarditis. They stand in some intimate relation with all infectious inflammations of the body. Their presence in healthy mouth secretion does not speak against this, it requiring some slight injury to allow this ever-present germ to develop into disease.

Anti-toxin of Pneumonia. (Klemperer.)

The injection of very diluted cultures of the virulent bacilli intravenously has produced an immunity in rabbits and guineapigs. The serum of such artificially immune animals when filtered

through a Chamberland filter and injected into a rabbit suffering with pneumonia, cured the same; or when injected into a susceptible animal produced in it immunity very quickly. This principle is ascribed to an anti-toxin formed in the tissues by the diluted proteids, and this anti-toxin neutralizes the toxicity of the strong virus.

Bacillus of Rhinoscleroma. (Frisch. 1882.) It was found in the tissue of a rhinoscleroma, but resembles the Friedlander bacillus in nearly every respect, and as the disease rhinoscleroma was not reproduced by the inoculation of the bacillus in animals, it can be considered identical. The growth, cultures, and properties are the same as the pneumobacillus of Friedlander (Diplococcus intracellularis meningitidis).

Weichselbaum claims to have found a special diplococcus in epidemic cerebro-spinal meningitis, which differs in a few respects from the pneumococcus of Fränkel: growth most abundant on blood-serum-round, white, shining colonies in 24 hours. It does not take Gram's stain; does not affect animals when injected subcutaneously. Inoculated into the meninges of the dog and goat, a meningitis has been produced, and when found in the exudate of the meninges lies in the protoplasm and nuclei of the leucocytes.

Micrococcus Tetragenus. (Koch. Gaffky).

Origin. Koch found this microbe in the cavity of a tuberculous lung. Gaffky, in 1883, studied its pathogenic actions and gave it the name it now bears.

Form.-Cocci which are gathered in the tissues in groups of four, forming a square, a tetrad. See Fig. 71. In artificial culture, sometimes found in pairs. A capsule of light gelatinous consistence surrounds each tetrad.

Properties. They are immobile; do not liquefy gelatine.

Growth. They grow well on all nutrient media at ordinary and brood temperatures; are facultative ærobic. They grow slowly. Colonies in gelatine plates. In two days, little white spots, which when on the surface form little elevations of a porcelain-like appearance; under low power they are seen very finely granulated.

Stab Culture.-Small round separated colonies along the needle-track, and on the surface a button-like elevation, a form of "nail culture." See Fig. 72.

Potato. A thick slimy layer which can be loosened in long shreds.

Staining.-Colored with the ordinary aniline stains. Gram's method also applicable. Pathogenesis.-White mice and guinea-pigs die in a few days of septicemia when injected with the tetragenus cultures, and the micrococcus is then found in large numbers in the blood and viscera. Field mice are immune.

In the cavities of tubercular lungs, in the sputum of phthisical and healthy patients, it is often found, but what action it has upon man has not yet been determined.

Capsule Bacillus. (Pfeiffer.)

Origin.-Stringy exudate and blood of a dead guinea-pig.

Form.-Thick little rods, sometimes in long threads. Large oval capsules in the stained preparations.

Properties.-Immotile, not liquefying, an odorless gas in gelatine cultures.

Growth. At ordinary temperatures, rapidly; facultative anærobin.

Gelatine Plates.—Oval points, and like a porcelain button on the surface.

Stab Cultures.-Like the pneumonia bacillus of Friedlander.

Potatoes.-Abundant growth, yellow color

and moist, coming off in strings.

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FIG. 72.

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Stab Culture. Micrococcus tetragenus.

Staining.-Hot fuchsin colors the capsule intensely; carefully decolorizing with acetic acid, the capsules are red or light violet around the deeply-tinged bacillus. Gram's method not applicable.

Pathogenesis. -Subcutaneously injected in mice, they die in 48 hours. Rabbits die when a large quantity is injected into

the circulation. The blood and juices have a peculiar stringy. fibrinous consistence.

Bacillus of Influenza. (Pfeiffer, 1892.)

A small bacillus about one-half the size of the bacillus of mouse septicæmia, and arranged in chain-form.

FIG. 73.

It develops

Bacillus influenzæ, from a gelatin culture; X 1000 (Itzerott and Niemann).

upon blood-serum agar. It is aërobic. Without movement; does not take the Gram stain. It is best stained with diluted carbol-fuchsin, the contrast-stain being Löffler's methyleneblue. Upon glycerine-agar, over which a drop of blood has been spread, in an incubator at the end of twenty-four hours a very delicate growth occurs, which resembles condensed moisture. It is found in the sputum and in the bronchial nasal secretions and blood of influenza patients, but cannot as yet be said to be the cause of influenza.

Micro-Organisms of Suppuration. The suppuration of wounds is due to the presence of germs. The knowledge of this fact is the basis of the antiseptic treatment in surgery; for when the microbes can be destroyed or their entrance prevented, the wounds are made clean and kept without suppurating. Various forms of bacteria have been found in septic processes, and