Form.-In the granular masses of an abscess cylindrical filaments are matted together, and radiating outward from this zone are club-shaped branches, as the petals of an aster. In the center of the granule are numerous cocci-like bodies, and some of the ovoid or club-shaped hyphens lie detached from the clusters. Through cultivation it was found that the ovules give rise to filaments, and they then form the ovules again.

Cultivation.-At 38° C. on glycerine-agar in a period of one to two weeks, pointed scales about the size of a millet-seed, center dry and prominent, margins hyaline, composed only of filaments, short and long, massed together, but no clubbed forms.

By some the clubs are considered the spore organs; by others they are thought to be encapsulated or thickened filaments.

Pathogenesis.-When a portion of the growth obtained in eggs was injected into the abdominal cavity of a rabbit, actinomycotic processes developed upon the peritoneum.

It usually gains access to the living body through a wound in the gum or some caries of the teeth. A new growth is formed, ulceration being first set up.

The new tissue, composed of round cells, then undergoes softening, purulent collections form and the normal structure is destroyed.

The usual seat is in the maxillary bones, but the fungus has been found in the lungs, tonsils, intestines, and various other organs in man and cattle.

Examination.-Well seen in the unstained condition. From the pus or scraping a small portion is taken and squeezed upon the glass slide; if calcareous matter is present, a drop of nitric acid will dissolve the same.

Glycerine will preserve the preparation.

Staining.-Cover-glass specimens stained best with Gram's method. Tissue sections should be stained as follows:Ziehl's carbol-fuchsin, ten minutes. Rinse in water. Conc. alcohol sol, of picric acid, five minutes. Rinse in water. Alcohol, 50 per cent., fifteen minutes. Alcohol absolute, clove oil, balsam.

The rays stained red, the tissue yellow.

Streptothrix Madura. (Vincent.)

Origin.-Found in the disease known as Madura foot, or Mycetoma, an ulceration affecting the feet, especially of individuals living in the tropics.

Form.-Branched filaments resembling the actinomyces streptothrix in the mycelia. Spores are seen.

Cultivation.-In liquid media containing vegetable infusions. growth occurs best. Temper

ature of 37° C. most suited. The colonies near the surface become colored red.

Agar.-Glazed colonies, at first colorless, then rose-colored, about the size of a pea, with the central part umbilicated and pale. Gradually the rose color fades.

Acid Potato.-A slow and meager growth.

Pathogenesis.-Only local reaction has been caused by inoculation in animals. In man the disease usually follows a slight injury and attacks the leg or foot, slowly forming a nodular growth, which in the course of months or a year begins to soften and ulcerate, and with the sero-pus are discharged numerous little granules, some black, some pink, containing

FIG. 93.

mycelia. The limb becomes Streptothrix Madura in a section of diseased tissue (Vincent). much deformed, the tissue

vascularized, and the degenerated area filled with the streptothrix filaments.

Staining. The organism itself stained with ordinary stains. Gram's method for the tissue.

Streptothrix Farcinica. (Nocard.) Bovine Farcy, Farcin du Bœuf.

Origin. A disease affecting cattle and giving rise to tuberclelike lesions in the lungs, liver, and spleen. Common in France, Form.-Small interwoven mass of threads arranged in tufts found in the centers of the tubercles.

Culture. At body-temperature in various media.

Bouillon.-Colorless masses irregular in size and shape.

Agar and Gelatine.-Small, rounded, opaque colonies, thicker at the periphery.

Potato.-Rapid growth of pale yellow dry scales, consisting of many spores.

Pathogenesis. Pure cultures introduced into the peritoneum of guinea-pigs give rise in 9 to 20 days to tubercle-like lesions. Subcutaneous injections cause abscesses with secondary involvement of the lymphatics, ending in recovery. Dogs, horses, and rabbits are immune.

Staining.-Wright's double stain for tissues; also Gram's.
Examination of Air, Soil, and Water.

Air. Many germs are constantly found in the atmosphere about us. Bacteria unaided do not rise into the air and fly about; they usually become mixed with small particles of dirt or dust and are moved with the wind. The more dust the more bacteria, and therefore the air in summer contains a greater number than the air in winter, and all the other differences can be attributed to the greater or less quantity of dust and wind.

Methods of Examination. The simplest method is to expose a glass or dish covered with gelatine in a dust-laden atmosphere or in the place to be examined. In the course of 24 to 48 hours colonies will be seen formed wherever a germ has fallen. But this method will not give any accurate results in regard to the number of bacteria in a given space; for such a purpose somewhat more complicated methods are needed, so that a certain amount of air can come in contact with the culture media at a certain regulated rate of speed.

Hesse's Method. This is the most useful of the various methods in vogue.

A glass cylinder, 70 centimetres long and 3.5 centimetres in diameter, is covered at one end, by two rubber caps, the inner

one having a hole in its centre 10 millimetres in diameter; and at the end B a rubber cork fits in the cylinder; through this cork a glass tube 10 mm. in diameter passes, which is plugged at both ends with cotton. The cylinder and fittings are first washed in alcohol and sublimate and then placed for one hour in the steam chamber.

Removing the cork of the cylinder, 50 cubic centimetres of sterile gelatine in a fluid condition are introduced and rolled out on the sides of the tube, after the manner of Esmarch, leaving a somewhat thicker coating along the under side of the

cylinder. The croscope, as the cylinder and its fittings are called, is placed upon an ordinary photographer's tripod and the glass tube, which passes through the rubber cork, connected with an aspirator, the cotton having first been removed from its

outer end. The aspirator consists of two ordinary wash-bottles connected with each other by a rubber tube, C. They are attached to the tripod with a small hook one above the other, the upper one half filled with water and slightly tilted.

FIG. 95.

Sand filter after Petri.

When the apparatus is wanted, the outer rubber cap at the end A of the aeroscope is removed, the air can then pass through the small hole in the other cap, and the germs fall upon the gelatine in the tube, the cotton in the small glass tube at the other end preventing the germs from getting out. The aspirator is set in use by tilting the upper bottle so that the water flows into the lower, this creates suction and draws the air through the aeroscope.

The amount entering estimated by the capacity of the wash-bottle. The rate at which it enters depending upon the rate of the flow of water, which can be regulated.

Hesse advises for rooms and closed spaces 1 to 5 litres, at the rate of 2 minutes a litre, and for open spaces, 10 to 20 litres at 4 minutes a litre. Plate cultures can be made from the colonies which develop in 8 to 10 days in the cylinder.

Petri's Method. The air pumped or sucked through sand filters, and the sand then mixed with gelatine.

Sand is sterilized by heating to redness, and while still warm placed in test tubes which are then plugged. (Sand which has been passed through a sieve with meshes 0.25 millimetres wide is the kind required.) A glass tube 9 centimetres long is provided with two portions of sand each 3 cm. long and cm. apart, little plates of brass gauze keeping the portions in position.

The tube and its contents now sterilized in hot air oven at 150° C., the ends having first been plugged with cotton.

One end of the tube is then fitted with a rubber cork through which passes a glass tube, which is connected with an aspirator (a hand-pump with a known capacity).