rapidly fatal form. The glanders organism soon loses its
virulence and even its vitality. Dry, it dies in about ten
days; placed in distilled water, in about five days; but kept
moist, or on culture media, it retains its vitality for about a
month, although its activity soon becomes considerably lessened.
These bacilli are readily killed at a temperature of 55° C; they
can pass through the kidneys, even when there is no lesion to be
made out either with the naked eye or under the microscope
(Sherrington and Bonome).
The glanders bacillus grows best in the presence of oxygen, but it may grow anaerobically; it then appears to have the power of forming toxin, either more in quantity or of greater activity than when it has access to a free supply of oxygen. This poison (mallein) is used for the purpose of diagnosing the presence of glanders. A cultivation is made in peptonized bouillon to which a small portion of glycerin has been added. The bacillus is allowed to grow and multiply at the temperature of the body for a month or six weeks; the organisms are then killed by heat and 0·5% carbolic acid is added. The cultivation is then filtered through a porcelain filter in order to remove the bodies of the bacilli, and the resulting fluid, clear and amber-coloured, should have the power, when injected in quantities of 1 c.c, of giving the specific reaction in an animal suffering from glanders; in a healthy animal 6 c.c. will give no reaction. The suspected animal should be kept at rest and in a warm stable for twenty-four to forty-eight hours before the test is applied. The temperature should be normal, as no proper reaction is obtained in an animal in which the temperature is high. This reaction, which is a very definite one, consists in a rise of temperature of from 2° to 4° F., and the appearance of a swelling of from 3 to 4 in. in diameter and from 1 to 112 in. in height, before the sixteenth or eighteenth hour; this swelling should continue to increase for some hours. It has been suggested that the injection of 120 to 115 c.c. of mallein, at intervals of two or three days, may be used with advantage in the treatment of glanders. Glandered horses seem to improve under this treatment, and then certainly do not react even to much larger doses of mallein. The mallein test has revealed the fact that glanders is a far more common and more widespread disease than was at one time supposed.
II.—To Higher Vegetable Parasites
Actinomycosis.—This disease is very prevalent in certain low-lying districts, especially amongst cattle, giving rise to the condition known as “sarcoma,” “wooden tongue,” “wens,” “bony growths on the jaw,” &c. It is characterized by the presence of a fungus, which, at first growing in the form of long slender threads that may be broken up into short rods and cocci, ultimately, as the result of a degenerative process, assumes the form of a “ray-fungus,” in which a series of club-like rays are arranged around a common centre (see Plate I., fig. 8). It is probably a streptothrix—Streptothrix Försteri. Numerous cases have been observed in the human subject. Suppuration and the formation of fistulous openings, surrounded by exuberant granulations, “proud flesh,” usually supervene where it is growing and multiplying in the tissues of the human body, and in the pus discharged are yellowish green or reddish brown points, each made up of a central irregular mycelium composed of short rods and spores, along with the clubs already mentioned. The mycelial threads may reach a considerable length (20 to 100μ); some of them become thicker, and are thus differentiated from the rest; the peripheral club is the result of swelling of the sheath; the filaments nearer the centre of the mycelial mass contain spores, which measure from 1 to 2μ in diameter. This fungus appears to lead a saprophytic existence, but it has the power of living in the tissues of the animal body, to which it makes its way through or around carious or loose teeth, or through abrasions of the tongue or tonsils. After the above positions, the abdomen, especially near the vermiform appendix, is a special seat of election, or in some cases the thorax, the lesions being traceable downwards from the neck. Any of the abdominal or thoracic organs may thus be affected. The process spreads somewhat slowly, but once started may extend in any direction, its track being marked by the formation of a large quantity of fibrous tissue, often around a long fistula. In the more recent growths, and in solid organs, cavities of some size, containing a soft semi-purulent cheesy-looking material, may be found, this mass in some cases being surrounded by dense fibrous tissue. When once a sinus is formed the diagnosis is easy, but before this the disease, where tumours of considerable size are rapidly formed, may readily be mistaken for sarcoma, or when the lungs are affected, for tuberculosis, especially as bronchitis and pleuritic effusion are frequently associated with both actinomycosis and tuberculosis.
Mycetoma, the Madura foot of India, is a disease very similar to actinomycosis, and, like that disease, is produced by a somewhat characteristic streptothrix. It usually attacks the feet and legs, however, and appears to be the result of infection through injured tissues. Under certain conditions and in long-standing cases the fungus appears to become pigmented (black) and degenerated.
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B.—Diseases due to Animal Parasites.
I.—To Protozoa
Malaria.—Following Laveran’s discovery, in 1880, of a parasite in the blood of patients suffering from malaria, our knowledge of this and similar diseases has increased by leaps and bounds, and most important questions concerning tropical diseases have now been cleared up. Numerous observations have been carried out with the object of determining the parasitic forms found in different forms of malaria—the tertian, quartan, and aestivo-autumnal fever—in each of which, in the red blood corpuscles, a series of developmental stages of the parasite from a small pale translucent amoebiform body may be followed. This small body first becomes lobulated, nucleated and pigmented; it then, after assuming a more or less marked rosette-shape with a deeply pigmented centre, breaks up into a series of small, rounded, hyaline masses of protoplasm, each of which has a central bright point. The number of these, contained in a kind of capsule, varies from 8 to 10 in the quartan, and from 12 to 20 in the tertian and aestivo-autumnal forms. There are certain differences in the arrangement of the pigment, which is present in larger quantities and distributed over a wider area in the somewhat larger parasites that are found in the tertian and quartan fevers. In the parasite of the aestivo-autumnal fever the pigment is usually found in minute dots, dividing near the pole at the point of division of the organism, along with it in the earlier stages (see Plate I., fig. 5). Here, too, the rosette form is not so distinct as in the parasite of tertian fever, and in the latter is not so distinct as in the quartan parasites. These dividing forms make their appearance immediately before the onset of a malarial paroxysm, and their presence is diagnostic. The process of division goes on especially in the blood-forming organs, and is therefore met with more frequently in the spleen and in bone-marrow than in any other situation. The parasites, at certain stages of their development, may escape from the red blood corpuscles, in which case (especially when exposed to the air for a few minutes) they send out long processes of protoplasm and become very active, moving about in the plasma and between the corpuscles, sometimes losing their processes, which, however, continue in active movement. In the aestivo-autumnal fever curious crescent-shaped or ovoid bodies were amongst the first of the parasitic organisms described as occurring in the blood, in the red corpuscles of which they develop. Manson maintains that from these arise the flagellate forms, all of which, he thinks, are developed in order that the life of the malarial parasite may be continued outside the human body. It is probable that most of the pigment found in the organs taken from
