Distemper may be defined as a feverish disease, always marked by rapid loss of strength and flesh, in proportion to the severity of the attack. It may occur at any period of life, and even more than once in the same individual; it is, however, generally met with in the puppy, and in most cases the dog is afterwards exempt. The essence of the disease appears to consist in a poisoned state of the blood, which may be either produced by contagion or by putrid emanations from filthy and overcrowded kennels; and it is from the efforts of nature to throw off this poison that the various symptoms are produced by which we know the disease. These symptoms differ according to the peculiar constitution of each dog, and to the state of the air and other causes which produce them. Hence it is usual to speak of distemper as either simple or attended with certain complications in the head, chest, belly, Ac. But, although they are all essentially the same disease, these variations may be conveniently described as - 1st, Mild Distemper; 2nd, Head Distemper; 3rd, Chest Distemper; 4th, Belly Distemper; and 5th, Malignant Distemper.

In Mild Distemper there are in almost all cases the following symptoms, which also show themselves in the other kinds, with the additional symptoms peculiar to each. The first thing noticeable is a general dulness (particularly shown in the eyes), accompanied by a dislike to play or take any kind of exercise, and by a want of appetite. Soon there appears a short cough, attended by a disposition to sneeze; and the dog often seems as if he hardly knew which of these acts to do first. The cough and sneezing are seldom heard while the dog is quiet, but when he is brought out of his kennel into the air, and particularly after he begins to play or run about, the mucous membrane is irritated and the coughing is set up, either by itself or alternately with sneezing. There is some slight thirst, a warm dry nose generally (but not invariably), a disordered state of the bowels, which may be either confined or relaxed, and a scanty secretion of high-coloured urine. In a few days the dog loses flesh and strength to a great extent, but then gradually recovers.

Head Distemper commences in the same way as the mild form, but the cough or sneezing is very slight, and sometimes there is not a vestige. On separating the eyelids, the whites are seen to be covered with blood-vessels loaded with dark blood, and a strong light seems to give pain. This kind of distemper is often indicated, soon after its commencement, by a fit, lasting a short time, and leaving a state of torpor from which the dog can with difficulty be aroused. If the brain is not relieved, the fits recur at short intervals, and the stupor increases, until the dog becomes quite insensible, and dies in a violent convulsion.

Chest Distemper appears to be an extension downwards into the chest of the irritation which produces the cough. It there generally sets up the kind of inflammation known as bronchitis, together with which, however, there is often inflammation of the substance of the lungs (pneumonia), or even of the external surface (pleurisy).

Distemper of the Belly is too often the result of mismanagement, produced either by the abuse of violent drugs or by neglect of attention to the secretions for some time previously. In the former case the bowels become very relaxed at the end of a week or ten days from the first commencement of a case of mild distemper, and then there is a constant diarrhoea, soon followed by the passage of large quantities of blood. This may be quite black and pitchy when it comes from the small intestines, or red and florid where the lower bowels are affected. Sometimes these symptoms appear of themselves, but generally they result from calomel or other violent medicines. When there has been neglect, and the bowels have been allowed to become confined, while at the same time the secretion of bile has been checked, a most dangerous symptom, known as " the yellows," shows itself, the name being given in consequence of the skin and white of the eyes being stained of a yellow colour, from the presence of bile.

This may occur without distemper, and then it is not so fatal; but when it comes on during an attack of this disease it is almost invariably followed by death.

Malignant Distemper may come on at first, the dog attacked being as it were at once knocked down by the severity of the poison; or it may show itself at the end of a week or ten days from the first commencement. It may follow either of the four kinds already described, being marked by an aggravated form of the symptoms peculiar to each; but there are some additional evidences of the poisoned state of the blood, which show themselves in the four stages into which the disease, when well marked, divides itself. These stages are - 1st, incubation, during which the disease is, as it were, hatching or brewing; 2nd, reaction, when nature is working herself up to throw off the poison; 3rd, prostration, following these efforts; and 4th, convalescence, wherein the constitution recovers its usual powers. In a well-marked case of malignant distemper these four stages average about a week or ten days each; and it is important to ascertain their existence, inasmuch as the treatment proper to each varies very considerably. The period of incubation is known by the symptoms described as common to mild distemper, as well as to the other kinds; but, in the malignant form, the strength is lost much more rapidly, while the appetite is almost entirely absent, and the secretions are very much disordered.

During the reaction, the pulse becomes quick and hard, the breathing is much hurried, and is often much quicker than the pulse without the existence of any inflammation. This is very important to notice, as, when such is the case, any lowering measures are highly improper ; but, on the other hand, the pulse may be very high and strong, and the breathing laboured, which, together with other unmistakable evidences afforded to the practised ear, prove the existence of inflammation, and require energetic and lowering treatment. At this time, also, are developed those dangerous affections of the brain, bowels, or liver, to which I have before alluded. When the stage of prostration sets in the whole system is thoroughly reduced, the dog is so weak that he is unable to stand, his appetite is often entirely gone - so that he must be drenched if he is to be kept alive; his gums, tongue, and teeth are coated with a black fur, and his breath is highly offensive. At this time an eruption of the skin generally shows itself, sometimes consisting in mere purple spots, in others of small bladders filled with yellow matter, but most frequently of bladders, varying in size from a pea to half a hen's egg, and containing matter more or less stained with purple blood, or occasionally blood alone.

This eruption is thickest on the skin of the belly and inside of the thighs, but sometimes it extends to the whole body. It is a favourable sign, taken by itself, though it generally attends upon severe cases. In the convalescence from malignant distemper, health gradually returns ; but without the greatest care in all respects a relapse is very apt to occur, and is then generally fatal.