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explanation of the occurrence of the organisms in Philadelphia waters can be given."

A number of interesting spirilla, more or less closely resembling that of Asiatic cholera, have been described from time to time. Their variation from the true cholera organism can best be determined by an examination of the following table, though for precise information the student will do well to look up the original descriptions, references to which are given in each case.

DIFFERENTIAL TABLE FOR SEPARATING ORGANISMS RESEMBLING THE CHOLERA SPIRILLUM.

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* "Berliner klin. Wochenschrift," 1884, Nos. 31 and 32. Ann. de l'Inst. Pasteur," t. 11, 1888, p. 482. "Archiv für Hygiene," XXI, 1894, p. 172. "Centralbl. f. Bakt.," etc., Bd. 11, 1887, p. 469. III" Hygienische Rundschau," 1893.

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+ Deutsche med. Wochenschrift," 1884, p. 632.

"Deutsche med. Wochenschrift," 1893, p. 799. "Archiv für Hygiene," xx1, 1894, p. 179. ***Deutsche med. Wochenschrift," 1885, p. 138.

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"Deutsche med. Wochenschrift," 1885. **"Centralbl. f. Bakt.," etc., XIV, p. 341.

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22 Archiv für Hygiene," XIX, 1893, p. 248. H" Hygienische Rundschau," IV, 1894, p. 721. 223 Deutsche med. Wochenschrift," 1892, p. 1124.

III" Journal of Experimental Medicine," July, 1896, p. 419, vol. 1, No. 3.

Chromogenic.

Fluorescent.

TYPHOID FEVER.

BACILLUS TYPHOSUS (EBERTH-GAFFKY).

General Characteristics.-A motile, flagellated, non-sporogenous, non-liquefying, non-chromogenic, non-aërogenic, aërobic and optionally anaërobic, pathogenic bacillus, staining by ordinary methods, but not by Gram's method. It does not form indol, acids from sugars, or coagulate milk.

Typhoid fever, "typhus abdominalis," enteric fever, "la fievre typhique," is a disease so well known and of such universal distribution, that no introductory remarks concerning it are necessary.

The bacillus of typhoid fever (Bacillus typhosus) was discovered in 1880 by Eberth* and Koch,† and was first secured in pure culture from the spleen and lymphatic glands four years later by Gaffky.‡

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Fig. 220.-Bacillus typhosus, from twenty-four-hour culture on agar. (From Hiss and Zinsser, "Text-Book of Bacteriology," D. Appleton & Co., publishers.)

Distribution.-The bacillus is both saprophytic and parasitic. It finds abundant opportunity, in nature, for growth and development, and, enjoying strong resisting powers, can accommodate itself to its environment much better than the majority of pathogenic bacteria, and can

*"Virchow's Archiv," 1881 and 1883.

"Mittheilungen aus dem kaiserl. Gesundheitsamt," 1, 45. Ibid., 2.

be found in water, air, soiled clothing, dust, sewage, milk, etc., contaminated directly or indirectly with the intestinal discharges of diseased persons.

Morphology. The organism is a short, stout bacillus, about 1 to 3 u (2 to 4 μ-Chantemesse, Widal) in length and 0.5 to 0.8 u broad (Sternberg). The ends are rounded, and it is exceptional for the bacilli to be united in chains. The size and morphology vary with the nature of the culturemedium and the age of the culture. Thoinot and Masselin,* in describing these morphologic variations, point out that

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when grown in bouillon the typhoid bacillus is very slender; in milk it is stouter; upon agar-agar and potato it is thick and short; and in old gelatin cultures it forms long filaments.

Flagella. The organisms are actively motile and are provided with numerous flagella, which arise from all parts of the bacillus (peritricha), and are 10 to 20 in number. They stain well by Löffler's method. The movements of the short bacilli are oscillating; those of the longer bacilli, serpentine and undulating.

Staining. The organism stains quite well by the ordinary methods, but loses the color when stained by Gram's method.

*"Précis de Microbie," Paris, 1893.

The bacillus gives up its color in the presence of almost any solvent, so that it is particularly difficult to stain in tissue.

When sections of tissue containing the typhoid bacilli are to be stained, the best method is to allow them to remain in Löffler's alkaline methylene-blue for from fifteen minutes to twenty-four hours, then wash in water, dehydrate rapidly in alcohol, clear up in xylol, and mount in Canada balsam. Ziehl's method also gives good results: The sections are stained for fifteen minutes in a solution of distilled water 100, fuchsin 1, and phenol 5. After staining they are washed in distilled water containing 1 per cent. of acetic acid, dehydrated in alcohol, cleared, and mounted. In such preparations the bacilli are always found in scattered groups, which are easily discovered, under a low power of the microscope, as reddish specks, and readily resolved into bacilli with the oil-immersion lens.

In bacilli stained with the alkaline methylene-blue solution, dark-colored dots (Babes-Ernst or metachromatic granules) may sometimes be observed near the ends of the rods.

The typhoid bacillus produces no endospores.

Isolation. The bacillus can be secured in pure culture from an enlarged lymphatic gland or from the splenic pulp of a case of typhoid. To secure it in this way the autopsy should be made as soon after death as possible, lest the coion bacillus invade the tissues, and cause confusing contaminations.

As the groups of bacilli are sometimes widely scattered throughout the spleen, E. Fränkel recommends that as soon as the organ is removed from the body it be wrapped in cloths wet with a solution of bichlorid of mercury and kept for three days in a warm room, in order that a considerable and massive development of the bacilli may take place. The surface is then seared with a hot iron and material for cultures obtained by introducing a platinum loop into the substance of the organ through the sterilized surface.

Cultures of typhoid bacillus may be more easily obtained from the blood of the living patients. (See "Blood culture," under the section "Bacteriologic Diagnosis.")

The bacilli can also be secured, but with much less certainty, from the alvine discharges of typhoid patients during the second and third weeks of the disease.

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