stream by the streptococcus pyogenes, and sometimes by other bacteria, may be demonstrated by cultures. The bacillus may also be found in company with other bacteria in ulcerated or excoriated surfaces on the skin, as well as in other suppurative processes, in individuals affected with diphtheria, and on the soiled linen of the patient. The infection of wounds with the bacillus diphtheria has also been observed without coincident diphtheria.

Bacillus of Typhoid Fever.'-Synonyms: Bacillus typhi abdominalis; Bacillus typhosus; Typhoid bacillus (see also Clinical Bacteriology).

Blood-serum.-Round, grayish, viscid-looking colonies,

FIG. 42.-Bacillus of typhoid fever, from a twenty-four-hour agar-agar culture; X 650 (Heim).

FIG. 43.-Diagrammatic representation of retraction of protoplasm, with production of pale points, in the bacillus of typhoid fever (Abbott).

Morphology.-Medium-sized bacilli with rounded ends,

1 Eberth: Virchow's Arch. f. Path. Anat., Bd. 81, 1880; Bd. 83, 1881; Gaffky: Mitth. a. d. Kais. Gesundheitsamte, Bd. 2, 1884.

generally short (Fig. 42), but sometimes long or thread-like, and frequently showing faintly-stained, sharply-defined areas in their protoplasm (Fig. 43).

Gelatin Slant.-Broad translucent streak with wavy, irregular margins. The gelatin is not liquefied. Growth is slower than that of the bacillus coli communis in the same medium.

An isolated colony, slightly magnified, on gelatin, is shown in Fig. 44.

Glucose-gelatin Stab.-Growth all along the line of inoculation in the form of confluent spherical grayish colonies, and

FIG. 44-Bacillus of typhoid fever: superficial colony two days old, as seen upon the surface of a gelatin plate; X 20 (Heim).

on the surface about the point of entrance of the platinum wire in the form of a circular translucent grayish layer. No production of gas-bubbles. No liquefaction.

Glucose Agar-agar.-Growth similar to that in the preceding. No gas-formation.

Litmus-milk.-No visible change.

Potato-Growth occurs, but it is usually invisible.

Dunham's Pepton Solution.-No indol-production-i. e. no red color appearing in the twenty-four- to forty-eighthour cultures after the addition of 5 drops of concentrated sulphuric acid, c. p., and I cubic centimeter of a solution of sodium nitrite, I: 10,000.

Motility. Very marked.

Flagella (Fig. 45) may be demonstrated by the special methods of staining described elsewhere.

Decolorized by Gram's method. Does not form spores. Bouillon.-Clouded, with the formation of some sediment. The clouding of the medium is not so marked as in the case of the bacillus coli communis. In general, the growth of the typhoid organism is not so vigorous on culture-media as is the growth of the bacillus coli communis.

When to a bouillon culture a small quantity of the blood

FIG. 45.-Bacillus of typhoid fever, from an agar-agar culture six hours old, showing the flagella stained by Löffler's method; X 1000 (Fränkel and Pfeiffer).

serum of a typhoid-fever patient is added, the bacilli lose their motility and aggregate in clumps ("serum reaction").

Pathogenesis.-The inoculation of animals is usually without results if moderate quantities of the organism are used. Sometimes, however, death occurs apparently from the effects of the toxic material injected.

Occurrence.-Found in the spleen in large numbers at autopsies in typhoid fever. Its presence may also be demonstrated in the intestinal lesions, mesenteric lymph-glands, liver, bile, kidneys, and blood of the heart. As a rule, the number of bacilli found in the liver, kidneys, and blood of

the heart is small. In the bile they may be numerous and may persist in it for a long period of time after the disease has subsided.

The typhoid bacillus may also occur in the suppurative sequelae of typhoid fever, especially those involving bones. In these conditions, however, it may be accompanied by the pyogenic cocci. Occurs in contaminated water.

Differential Diagnosis between the Bacillus of Typhoid Fever and the Bacillus Coli Communis.-The most important points of difference between these two organisms are as follows, and to distinguish with certainty between them it is necessary that attention be paid to all of them:

Motility. The typhoid bacillus is actively motile, the bacillus coli communis not motile or exceptionally motile. Potato Cultures.-The typhoid bacillus usually grows invisibly, the bacillus coli communis as a dirty, slimy layer.

Gas-production in Media containing Glucose.—The bacillus coli communis produces gas, the typhoid bacillus does not. Litmus-milk Cultures.-The bacillus coli communis changes the blue color of the medium to a pink color and usually coagulates the milk. The typhoid bacillus produces no visi change.

Indol-production.-The bacillus coli communis produces indol, the typhoid bacillus does not.

Serum or Clump Reaction.-The typhoid bacillus shows the clump reaction, while the bacillus coli communis does not. As it is not always possible to have a typhoid serum at hand by which to determine whether this reaction is present, a stock of dried blood from a typhoid case, contained in filter-paper, may be kept ready for use. That this is quite practicable has been recently shown by Dr. Mark W. Richardson. The blood may be obtained from the heart at the autopsy of a typhoid-fever case by soaking a piece of filter-paper with it. This is allowed to dry, and then is cut into pieces about 1 cm. square. When it is desired to make the test, one of these pieces is extracted with ten or fifteen drops of water, and a drop of this extract is mixed with a drop of an eighteen- to twenty-four-hour bouillon culture

on a slide, covered with a cover-glass, and examined with the high-power dry lens. Dr. Richardson has found that the blood under these conditions retains for months its "clumping" power with reference to the typhoid bacillus.

Other differences are the production of a red color in litmus-lactose agar-agar by the bacillus coli communis, and no change in color of this medium by the typhoid bacillus, and the slower and less vigorous growth of the typhoid bacillus in culture-media.

Bacillus Coli Communis.'-Synonyms: Bacterium coli commune; Colon bacillus.

Blood-serum.-Rounded, grayish-white, slightly elevated,

viscid-looking colonies, which may attain a diameter of 3 mm. after twenty-four hours in the incubator.

Morphology.-A medium-sized bacillus with rounded ends, often short or even coccus-like, but may grow in long forms (Fig. 46). Faintly staining, sharply defined areas are present in the protoplasm.

Gelatin Slant.-Grayish translucent strip with wavy margins. The gelatin is not liquefied. Growth is more rapid than in the case of the typhoid bacillus.

1 Escherich: Fortschr. d. Medicin, 1885, Nos. 16, 17.