CHAPTER IV.

MEASLES.

IN 1892, Canon and Pielicke, after the investigation of fourteen cases of measles, reported the discovery of a specific bacillus in the blood in that disease.

The organism is quite variable in size, sometimes being quite small and resembling a diplococcus, sometimes larger, and occasionally quite long, so that one bacillus may be as long as the diameter of a red bloodcorpuscle.

The discovery was made by means of a peculiar method of staining, as follows: The blood is spread in a very thin, even layer upon perfectly clean cover-glasses, and fixed by five to ten minutes' immersion in absolute alcohol. These glasses are then placed in a stain consisting of

Concentrated aqueous solution of methylene blue, 40; 0.25 per ct. solution of eosin in 70 per ct. alcohol, 20; Distilled water,

40,

and stood in the incubator at 37° C. for from six to twenty-four hours. The bacilli do not all stain uniformly.

The discoverers of the bacillus claim to have made it grow several times in bouillon, but failed to induce a growth upon other media.

The bacilli do not stain by Gram's method; they seem to have motility; no spores were observed. They were found not only in the blood, but also in the secretions from the nose and eyes.

They are said to persist through

out the whole course of the disease, even occasionally being found after the fever subsides.

Czajrowski asserts that the bacillus can be cultivated upon various albuminous media except gelatin and agar. On glycerin agar-agar, especially with the addition of hemotogen, and on blood-serum, they should grow in three or four days with an appearance like that of dewdrops. Under the microscope the colonies are structureless. Mice die of a septicemia after a subcutaneous inoculation.

CHAPTER V.

BUBONIC PLAGUE.

THE bacillus of bubonic plague (Fig. 102) seems to have met an independent discovery at the hands of

Yersin and Kitasato in the summer of 1894, during the activity of the plague then raging at Hong-Kong. There seems to be not the slightest doubt that the micro-organisms described by the two observers are identical.

The bubonic plague is an extremely fatal infectious disease, whose ravages in the hospital in which Yersin made his observations carried off 95 per cent. of the cases. It affects both men and animals, and is characterized by sudden onset, high fever, prostration, delirium, and the occurrence of lymphatic swellings-buboesaffecting chiefly the inguinal glands, though not infrequently the axillary, and sometimes the cervical, glands. Death comes on in severe cases in forty-eight hours. If the case is of longer duration, the prognosis is said to be

better. Autopsy in fatal cases reveals the enlargement of the lymphatic glands, whose contents are soft and sometimes purulent.

The studies of Kitasato and Yersin showed that in blood drawn from the finger-tips and in the softened contents of the glands a small bacillus was demonstrable. The organisms are small, stain much more distinctly at the ends than in the middle, so that they resemble diplococci, and in fresh specimens seem to be surrounded by a capsule. Kitasato compares the organism to the well-known bacillus of chicken-cholera. It is feebly motile, and does not seem to form spores. Nothing is said about the presence of flagella.

When cultures are made from the softened contents of the buboes, the bacillus can be obtained almost or quite pure, and is found to develop upon artificial culturemedia. In bouillon a diffuse cloudiness results from the growth, as observed by Kitasato, though in Yersin's observations the cultures more nearly resembled erysipelas cocci, and contained zoöglea attached to the sides and in the bottom of a tube of nearly clear fluid.

In gelatin puncture-cultures the development is scant. The medium is not liquefied (?); the growth takes place in the form of a fine duct, little points being seen on the surface and in the line of puncture.

Upon agar-agar-glycerin agar-agar is best-the bacilli grow freely, the colonies being whitish in color, with a bluish tint by reflected light. Under the microscope they appear moist, with rounded, uneven edges. The small colonies are said to resemble little tufts of glasswool; the larger ones have large round centres. Microscopic examination of the bacilli grown upon agaragar reveals the presence of long chains resembling streptococci.

Upon blood-serum the growth at the temperature of the incubator is luxuriant. It forms a moist layer of a yellowish-gray color, and is unaccompanied by liquefaction of the serum.

Upon potatoes no growth occurs at ordinary temperatures. When the potato is stood away for a few days in the incubator, a scanty, dry, whitish layer develops.

Kitasato found that mice, rats, guinea-pigs, and rabbits are all susceptible. When blood, lymphatic pulp, or pure cultures are inoculated into them, the animals become ill in from one to two days, according to size. Their eyes become watery, they begin to show disinclination to take food or to make any bodily effort, the temperature rises to 41.5° C., they remain quietly in a corner of the cage, and die with convulsive symptoms in from two to five days.

According to Yersin, an infiltration can be observed in a few hours about the point of inoculation. The autopsy shows the infiltration to be made up of a yellowish gelatinous exudation. The spleen and liver are enlarged, the former often presenting an appearance much like an eruption of miliary tubercles. Sometimes there is universal swelling of the lymphatic glands. Bacilli are found in the blood and in all the internal organs. Very often there are petechial eruptions during life, and upon the inner abdominal walls there are occasional hemorrhages. The intestine is hyperemic, the adrenals congested. There are often sero-sanguinolent effusions into the serous cavities.

Kitasato found that pigeons were not susceptible. Animals fed upon cultures or upon the meat of others dead of the disease became ill and died with typical symptoms. When he inoculated animals with the dust of dwelling-houses in which the disease had occurred, some died of tetanus, one from plague. Many rats and mice in which examination showed the characteristic bacilli died spontaneously in Hong-Kong.

Yersin showed that flies also die of the disease. Macerating and crushing a fly in bouillon, he not only succeeded in obtaining the bacillus from the medium, but infected an animal with it.

Yersin found that when cultivated for any length of