tained in a culture tube. Cultures in nutritive gelatine were always made parallel with liquid cultures. The surface was scorched, and a straight platinum wire, soldered to a glass rod, was made to pierce the scorched surface and moved about in the spleen tissue, then the gelatine was pierced with it. Each tube was inoculated three times in this manner, the spleen tissue being pierced each time in a different direction. Plate III, Fig. 3, shows the three needle tracks after two days, dotted with colonies of the bacterium of swine-plague.

Cultures from the blood were made in the same way. After carefully removing the sternum and the pericardium, the surface of the right ventricle was scorched, an incision made along this area, and a looped or straight platinum wire introduced, as the occasion demanded. Cultures from the lymphatic glands, from the liver, and serous exudates may be made in the same way. Culture tubes, used for both solid and liquid cultures, were those described in the First Annual Report of the Bureau, p. 228. They have been so invariably successful that the ordinary plugged test tube was entirely discarded, and used only for storing gelatine to be used for plate cultures.

DESCRIPTION OF PLATES I, II AND III.

ILLUSTRATING SWINE-PLAGUE AND ROUGET.

PLATE I.-Ulcerated cæcum of pig affected with swine-plague, laid open. The mucous membrane of the ileo-cæcal valve is near the center of the figure and the small intestine with the cut end tied, above. The smallest ulcers are of a uniformly yellow color; the larger ones with zones of different color; the largest, brownish or blackish in appearance.

PLATE II, FIG. 1.-Pipette with rubber bulb c and constriction at a for collecting and preserving pathological effusions; b, glass wool plug (x ). The capillary portion is drawn too large.

FIG. 2.-The same pipette with the constriction at a sealed in the flame, the portion containing the glass wool plug and capped with rubber bulb removed. FIG. 3.-A simple form of culture cell; a, an ordinary "solid watch glass; b, cover; c, a cover glass, attached to a small block of glass, d, on the lower side of the cover b (x f). FIG. 4. Pasteur's second vaccine for rouget; dried on cover and stained in an aqueous solution of methyl-violet; mounted in xylol balsam; drawn with camera lucida (Abbe), Zeiss homogenous objective, ocular 2. The bacilli of rouget are seen among the larger bacilli as slender curves or broken lines. FIG. 5.-Drawn same as Fig. 4 cells from a dried cover-glass preparation from the lungs of a mouse inoculated with the second vaccine. Most of the bacilli are within the protoplasm of the cells. FIG. 6. Culture in meat-infusion peptone gelatine inoculated from plate cultures of Pasteur's vaccine I, twelve days old. The appearance is that of a row of faintly circumscribed, cloud-like masses in the track of the needle, which is itself scarcely visible as a delicate line. No liquefaction perceptible. PLATE III, FIG. 1. From a cover-glass preparation of the spleen of a pig affected with swine-plague. Drawn with Abbe's camera lucida homogenous, ocular 2 (x 800); a, red blood corpuscles distorted; b, the bacteria of swineplague. FIG. 2.-Various colonies from gelatine plates; a, imbedded in the gelatine layer; b, growing on the surface of the layer c, c', c', growing between the gelatine layer and the glass plate; a, b, about five days old (x 73); c, c′, c“, about seven days old (x 100); a fails to give the idea of solidity. The colony itself is either spherical or spheroidal; b, on the other hand, is flattened; c, c', c', the margins gradually attenuate and become lost to view.

FIG. 3.-Nutritive gelatine inoculated with a platinum wire from the spleen of pig No. 114; about three days old. Natural size. a. The colonies developed from individual microbes.

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DESCRIPTION OF PLATES IV TO VII.

TO ILLUSTRATE THE APPEARANCES PRESENTED BY THE GROWTH OF BACILLUS LUTEUS (SUIS) IN DIFFERENT MEDIA.

PLATE IV.-Colonies of the bacillus on gelatine plates.

FIG. 1 represents the appearance of a plate culture about twenty-four hours after preparation. Some colonies much further advanced than others (natural size).

FIG. 2.-A colony about one day old (x 50).

FIG. 3.-A colony somewhat older, presenting very fine radial stria and with margin no longer regular (x 50).

FIG. 4.-A colony which has reached the surface of the gelatine layer and produced a hemispherical depression by liquefying the gelatine. The motile bacilli have moved in part to the outermost limit of the liquefied area (x 17). PLATE V.-Figs. 1, 2, and 3 represent cultures in beef extract of bacillus luteus of different stages.

FIG. 1.-About two days old.

FIG. 2.-Eleven days old.

FIG. 3.-Thirty-seven days old.

FIG. 4.-A culture in sterilized milk about ten days old, showing the separation of the solid and liquid portion and the coloring of the latter.

FIG. 5.-Represents a culture in milk about forty-five days old. The casein has been almost consumed, a small remnant being left in the bottom of the tube.

The liquid portion has become deeply tinted; a whitish membrane with yellow patches rests on the surface of the liquid.

FIG. 6.-Growth of the bacillus on agar-agar, about four days old; the substratum has already assumed a yellowish tint.

PLATE VI.-Figs. 1, 2, 3, 4, and 5 represent successive stages of the growth of bacillus luteus in meat infusion peptone gelatine.

FIG. 1.-About twenty hours after inoculation; the upper portion of the needle track represented by a liquefied conical mass.

FIG. 2.-About forty-four hours old; the liquefied area has increased considerably; the entire surface layer has become liquid to a depth of 3 to 4mm.

FIG. 3. About sixty-eight hours old; Fig. 4 four days old, and Fig. 5 seven days old, illustrate the downward extension of the liquefying process until most of the gelatine has become involved. From Fig. 3 on the bacillus begins to form a surface membrane upon the liquid gelatine.

FIG. 6.-Culture in coagulated blood serum about nineteen days old. The different stages of growth resemble those on gelatine in a general way. Nearly all of the serum has become liquid; the upper layer has assumed a green color and is now covered with a brittle, white, bacillar membrane.

FIG. 7.-Represents a blood serum culture about forty days old. The entire mass is liquefied. A whitish deposit rests upon the bottom of the tube and a membrane covers the surface of the serum. The color being diffused through more liquid. is not so deep as that of Fig. 6.

PLATE VII.-Growth of the bacillus luteus (suis) on boiled potato.

FIG. 1.-Potato twenty hours after inoculation. A faint rose color about the track of the needle fading away into the surrounding surface.

FIG. 2.-Same culture about five days old; the growth appears as a narrow, elevated, reddish strip with wavy margins.

FIGS. 3 aud 4.-Potato cultures both about five days old. In Fig. 3 the change of color from a reddish to a dirty greenish tint is but partially completed. In Fig. 4 the growth has spread over the entire surface of the potato and discolored it uniformly. A few drops of sterile veal peptone had been added before inoculating. This probably aided the spontaneous movement of the bacilli and accounts for the invasion of the entire surface.

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