The tumors and abscesses wherever they may be are all found to be the same in origin by the presence of the actinomyces fungus. When they are incised, a very close scrutiny with the naked eye, or, at most, a hand lens, will reveal the presence of minute grains which vary from a pale-yellow to a sulphur-yellow color. They may be very abundant or so few as to be overlooked. They are embedded in the soft tissue composing the tumor or in the pus of the abscess. With a needle they are easily lifted out from the tissue, and then they appear as roundish masses about one-half millimeter (1/50 inch) in diameter. To anyone familiar with the use of a microscope the recognition of these grains or particles without any previous preparation is a comparatively easy task.
When examined in the fresh condition under a microscope magnifying up to 250 diameters the general structure is made out without much difficulty. These grains consist of collections of minute, roundish masses. Their outer surface is made up of club-shaped bodies all radiating from the center of the mass (see [Pl. XXXIX], fig. 2), somewhat like a rosette. If the fungus is crushed, the interior is found made up of bundles of very fine filaments, which are probably continuous into the club-shaped bodies. The addition of a dilute solution of caustic soda or potash greatly aids the examination, as it removes the layer of cells adhering to the fungus, which obscures the structure. Now and then these grains are found to be in a calcified condition. The exterior is incrusted in lime salts, which are dissolved by adding some weak dilute acid, like acetic acid. Only by this procedure can the fungus be definitely recognized when in a mummified condition.
These are the bodies whose presence causes sufficient irritation in the tissues into which they find their way to set up inflammatory growths. These growths increase as the fungus continues to multiply until they reach enormous dimensions, if the affected animal is permitted to live long enough. The true nature of this parasite is not yet definitely settled, although many excellent observers have occupied themselves with it. According to earlier observers, it is a true fungus. Later ones are inclined to place it among the higher bacteria. Present knowledge concerning the actinomyces growth indicates that it should be classified with the higher bacteria or trichomycetes.
Whatever the situation of the disease caused by actinomyces may be, its nature is fundamentally the same and peculiar to the fungus. The pathological details which make this statement clear can not be entered upon in this place, nor would they be of any practical value to the farmer. We will simply dwell upon a few obvious characters.
The consistency of the tumor varies in different situations according to the quantity of fibrous or connective tissue present. When very little of this is present the tumor is of a very soft consistency. As the quantity of connective tissue is increased the tumor is firmer and of a more honeycombed appearance. The individual actinomyces colonies are lodged in the spaces or interstices formed by the meshwork of the connective tissue. There they are surrounded by a mantle of cellular elements which fill up the spaces. By scraping the cut surface of such a tumor these cell masses inclosing the fungi come away, and the latter may be seen as pale-yellow or sulphur-yellow specks, as described above.
Location of the disease.—In cattle the disease process may be located both externally, where it is readily detected, and in internal organs. Its preferred seat is on the bones of the lower and upper jaws, in the parotid salivary gland in the angle of the jaw, and in the region of the throat. It may also appear under the skin in different parts of the body. Internally it may attack the tongue and appear in the form of a tumor in the mouth, pharynx, or larynx. It may cause extensive disease of the lungs, more rarely of the digestive tract.
It appears, furthermore, that in certain districts or countries the disease seems by preference to attack certain parts. Thus in England actinomycosis of the tongue is most prevalent. In Denmark the soft parts of the head are most prone to disease, while in Russia the lips are the usual seat. In certain parts of Germany actinomycotic tumors are most frequently encountered in the throat region and in the jawbones.
A description of actinomycosis of the jaw (lumpy jaw) and of the tongue has already been given in a previous chapter, and hence they will be dealt with here only very briefly. When the disease attacks the soft parts of the head a rather firm swelling appears, in which are formed one or more smaller projecting tumors, varying from the size of a nut to that of an egg. These push their way outward and finally break through the skin as small, reddish, funguslike bodies covered with thin sloughs. Or the original swelling, in place of enlarging in the manner described, may become transformed into an abscess which finally bursts to discharge creamy pus. The abscess cavity, however, does not disappear, but is soon filled with fungus-like growths, which force their way outward through the opening.
When the tumors are situated within the cavity of the pharynx they have broken through from some gland, perhaps beneath the mucous membrane, where the disease first appeared, and hang or project into the cavity of the pharynx, either as pendulous masses with slender stems or as tumors with broad bases. Their position may be such as to interfere with swallowing and with breathing. In either case serious symptoms will soon appear.
The invasion of the bones of the jaws by actinomycosis must be regarded as one of the most serious forms of the disease. ([Pls. XXXIX], [XL].) It may start in the marrow of the bone and by a slow extension gradually undermine the entire thickness of the bone itself. The growth may continue outward, and after working its way through muscle and skin finally break through and appear externally as stinking fungoid growths. The growth may at the same time work its way inward and appear in the mouth. The disease may also begin in the periosteum, or covering of the bone, and destroy the bone from without inward.