It is now generally admitted that this disease is similar to typhus fever in man, and should be treated in much the same manner.

The essence of the disease is some poison admitted from without, or developed within the blood, by which the various secretions are either totally checked, or so altered as no longer to purify the system. The exact nature of this poison is beyond our present state of knowledge, but from analogy there is little doubt that it resides in the blood. As in all cases of poison absorbed in the system, there is a most rapidly depressing effect upon the muscular powers, which is to be expected, inasmuch as their action requires a constant formation of new material from the blood. As this is retarded in common with all other functions, the muscles waste away rapidly, and their contractions are not performed with any strength. The disease is sometimes conveyed by infection. At others it is developed in the body; just as in the case of fermentation in vegetable substances, there may be a ferment added to a saccharine solution, by which the process is hastened, although if left to itself, it will come on in due course.

The symptoms are various; they may be divided into two classes, one of which comprises those always attending upon distemper; the other may or may not be present in any individual attack. The invariable symptoms are, a low insidious fever, with prostration of strength to a remarkabb degree, in proportion to the duration and str3ngth of the attack, and rapid emaciation, so that a thick muscular dog often becomes quite thin and lanky in three days. As a part of the fever, there is shivering, attended by quick pulse, hurried respiration, loss of appetite, and impaired secretions. Beyond these, there are no signs which can be called positively invariable, though the running at the eyes and nose, and the short husky cough, especially after exercise, are very nearly always present. The accidental symptoms depend upon the particular complication which may exist; for one of the most remarkable features in distemper is, that, coupled with the above invariable symptoms, there may be congestion, or inflammation of the head, chest, bowels, or skin.

In one case the disease may appear to be entirely confined to the head, in another to the chest, and in a third to the bowels; yet it results from the same cause in each case, and requires the same general plan of treatment, modified according to the seat of the complication.

When distemper is the result of neglect, it generally succeeds some other disease which may have existed for an indefinite period. The ordinary course of an attack of distemper, when epidemic, or the result of contagion, is as follows: general dullness or lassitude, together with loss of appetite are first observed. A peculiar husky cough generally follows in a day or two, with sounds as if the dog were trying to discharge a piece of straw from his throat. It always comes on at exercise after a gallop. With this there is also a tendency to sneeze, but not so marked as the "husk " or "tissuck " which may occur in common "cold" or influenza, and is then usually more severe, and also more variable in its severity; soon going on to inflammation, or else entirely ceasing in a few days. In distemper, the strength and flesh rapidly fail and waste, while in common "cold," the cough may continue for days without much alteration in either; this is one of the chief characteristics of the true disease. There is, also, generally a black pitchy condition of the faeces, and the urine is scanty and high-colored. The white of the eyes is always more or less reddened, the color being of a bluish red cast, and the vessels being evidently gorged with blood.

When the brain is attacked, the eyes are more injected than when the bowels or lungs is the seat of complication. The corners of the eyes have a small drop of mucus, and the nose runs more or less, which symptoms, as the disease goes on, are much aggravated, both eyes being glued by brownish matter. The teeth are also covered with a blackish brown fur. These are the regular symptoms of a severe attack of distemper, which gradually increases in severity to the third, fourth, or fifth week, when the dog dies from exhaustion, or from disease of the brain, lungs, or bowels, marked by peculiar signs in each case. In this course the disease may be described as passing through four stages or periods: 1st, that in which the poison is spreading through the system, called the period of inculation; 2nd, that in which nature rouses her powers to expel it, called the period of reaction; 3rd, the period of prostration, during which the powers of nature are exhausted, or nearly so, by the efforts which have been made; an;l 4th, the period of convalescence.

On the average, eacli of these will occupy a week or ten days, varying with the mildness or severity of the attack.

When the head is attacked, there may or may not be a running from the nose and eyes; but more usually there is some evidence of congestion in these organs, the eyes being weak and glued up with the mucus, and the nose running more or less. A fit is, however, the clearest evidence of brain affection, and, to a common observer, the only reliable one. Sometimes there is stupor without a fit, gradually increasing until the dog becomes insensible, and dies. At other times, a raving delirium comes on, easily mistaken for hydrophobia, but distinguished from it by the presence of the premonitory symptoms, peculiar to distemper. This is the most fatal complication of all, and, if the dog recovers, he is often a victim to palsy or chorea for the rest of his life.

If the lungs are attacked, there is very rapid breathing, with cough, and generally a considerable running from the eyes and nose, accompanied with expectoration of thick frothy mucus. If inflammation of the lungs is established, the danger is as great as when the head is the seat of the malady.