HOG CHOLERA-SWINE PLAGUE.

Hog cholera or swine plague is a specific infectious disease, peculiar to swine only, and originates in a specific micro organism. Its source of primary and original development is in the earth and earthy or refuse matters, whence the swine become infected and again in turn infect the same kind of material through their excreta, or it may be through their dead bodies. The disease is a blood poison induced in the swine by means of a secretion from specific germs, hence it is a septicaemia and it is an extra organismal septicaemia, because it finds its primary origin outside the animal organism. It is infectious, but not contagious. Its secondary lesions are pneumonia, and those of the large intestine; though bronco pneumonia, and certain intestinal lesions may occur about the same time as the septicaemia, when the infecting organisms gain an entrance by either of these tracts. The disease is extensively distributed over the temperate portion of the North American continent. No State seems to be exempt from it, whilst it prevails to a greater extent in the Middle Western States than in those North and South, and those East and West of this section. In no single State is the annual loss from this disease approximately known. The disease is known to prevail in Great Britain, and on the continent of Europe. It was first recognized in this country between 1840 and 1850. The scientific investigation of the disease is of very recent date. It has been charged that it is of American origin, but the evidence is against such charge; and it is more than probable that it was known to the ancients, as among the diseases of animals de scribed by Aristotle is one of swine that will pass as a fair description of the disease under consideration. Hog cholera is a specific disease dependent upon a specific germ. As has been already said, it is dependent for its origin upon an extra organismal micro-organism whose natural habitat is in the earth, and earthy or refuse material. Its primary source is always in the earth, and earthy material, and never in the hog until it has en

tered it, and infected it from these outside media. The causes of swine plague are everything that can exert an influence in extending the disease over a section of country by dispersing its specific cause, or anything that can possibly protect or support the life of that cause-the specific germ upon which it is dependent. Among the causes the first in importance is the diseased wine, then the pens or yards in which such have been; material conveyed from such pens or yards to other places which offer favorable conditions for the preservation of the life of the specific cause, or for its further development; anything which can convey such material-persons who visit their neighbor's hog yards after being in infected pens, dogs, fowls, rats, &c. The conveyances of common carriers, cars, wagons that have been used to convey diseased swine, or manure or straw from infected pens, the dead bodies of infected swine, and water courses running through infected yards. Could all these and other causes of distributing infection be thoroughly dealt with, there would be but little trouble in wiping the disease out of existence; but it has been known for years that the disease was infectious, and that its extension was due to the causes above enumerated. The fault is partly due to the indolence and carelessness of the parties interested, and partly to the want of authoritative direction on the part of some governing body.

The disease is a specific eruptive fever peculiar to the hog. It does not necessarily attack all animals exposed to it, nor is it always equally fatal. The incubative period of the disease is naturally about ten or twelve days, but it may develop in less time. Its duration may extend from two or three days to as many weeks or even months; though it may prove fatal in as many hours from the time when the animal is first noticed to be sick. Its invasion may be very pronounced or its special and characteristic symptoms may be slowly and insidiously developed. I have said it is a specific eruptive fever. In the earliest stages there is more or less fever, the temperature is elevated, the pulse increased in frequency, the bowels may be either constipated or relaxed, and there is a husky bronchitic cough. The animals seek to isolate themselves. They seek warmth by burrowing in the straw or litter. When lying down they refuse to rise, or rise stiffly and unwillingly and move with an awkward gait, and soon exhibit evidences of exhaustion. The ears frequently lop over and present a congested appearance. The conjunctiva is injected and there is frequently a lachrymation, or discharge from the eyes of a glutinous mucus, which, with the dust or dirt adhering to it gives to the animal a peculiar frowsy look. In the more advaced stages the above symptoms become aggravated and more pronounced. The temperature rises, the pulse becomes more rapid, the breathing more hurried and jerky, the urine scanty and high colored, frequently emitting a peculiar and characteristic odor, weakness increases and the movements become more unsteady. Food is refused, or taken very sparingly,

though there may be great thirst. The irregularity of the bowels becomes more marked, the faeces become of a dark color, pasty and of a very unpleasant but characteristic odor. There may be some blood discharged from the eyes and nostrils. Should the bowels become inflamed, a diarrhoea replaces constipation, the discharges being of a dirty chocolate, or yellow ochre color, with the above mentioned characteristic odor. At other times, when the bowels are constipated, the contents accumulate in the large intestine, undergo decomposition, liberate sulphuretted hydrogen gas, and produce tympany with distension. When the lungs are affected the breathing becomes labored and hurried and the cough becomes distressing, with catarrhal discharge from the nose and eyes. There is often a short, hollow grunt made in breathing; and examination of the chest shows signs of consol idation. The skin of the ears and abdomen is frequently purplish and the extremities cold; not unfrequently a bloody foam issues from the nostrils and the breathing becomes gasping. Sometimes the brain is involved and the animal presents a stupid appearance, wanders aimlessly about and staggers like a drunken man, often falls helplessly, or if excited, is thrown into convulsions. At times the head is bored into a corner or thrust into the litter, producing stertor. If the spinal cord or its membranes are affected, there will be muscular twitchings, spasm, and partial, followed by total, paralysis. The external local lesions will be found in the skin; they consist of discolorations, vesications and pustulations, sloughs and desquamation. The discolorations vary from pale blue or light red to a dark, livid blue, purple or black. At times there may be merely a slight erythematous blush on the skin of the abdomen, the vulva, the hocks, the ears, the throat, or the inside of the thighs, or only a little blueness of the ears. The discoloration may be diffuse, or in discrete patches. Exciting the animal or lifting it by the hind legs will increase the discoloration. In a few days, or it may be in a few hours, the discolorations become more distinct, so in recovery it gradually fades away. A desquamation of the skin, or even a sloughing in patches may occur. Vesication and pustulation is rarely a primary lesion, generally coming on in the course of the disease. Sloughs are sometimes seen on the ears or on the back, and are due to capillary or haemorrhagic lesions. The tail is often lost, especially in young hogs. Desquamation is not peculiar to this disease, but may occur as a common result in any fever. The importance of a correct diagnosis in this disease cannot well be over rated, as upon it will depend the prevention or medical measures adopted. The diseases with which it is most likely to be confounded are pneumonia, purpura haemorrhagica, urtieoria, measles, eryesipelas, variola and anthrax. Practically, whenever a large number of hogs are found dying simultaneously over a large area of country with symptoms of bowel or pulmonary derang ment and with skin eruptions, it may safely be assumed that they are suffering from swine fever, as pigs are not in this country

subject to any other fatal malady of an epidemic type. In making a post mortem examination of a hog supposed to have died of swine plague, it is best to first remove the stomach and intestines and lay them aside until the carcass has been examined, for it is best to look first to the general condition of the tissues of the body, and the blood; next to the pulmonary lesions; then to the gastro-intestinal lesions, and the lymphatics. The appearance of the carcass will be modified by the fact as to whether the animal has died a natural death or been killed; as to whether the blood has been abstracted from the body, and whether the carcass has been properly dressed, scalded and scraped; for under such conditions the skin lesions will be more marked. If the hog has been well fed, and the duration of the disease short, there will not be much shown by the general condition of the carcass, but if the disease has lasted some time, and there has been much bowel or lung trouble, and emaciation has set in, the carcass will be pale, flabby and moist. The blood, in the early stages, and even in advanced stages, may not present any marked physical changes, or it may be dark in color, and thick and tarry in consistence; or it may resemble a mixture of red brick dust in s me calloid substance. The systemic lesions are extravisations of blood, and effusion of serum and lymph. The skin extravisations may be confounded with bruises upon the surface from blows with sticks. The extravisations are rarely pronounced in the muscular tissue, but will be found. in the inter-muscular spaces. The serous extravisation is common into the peritoneum, the pericardium, within the renal capsule, or within the sircus capsule of the liver or spleen, or within the cerebral meninges. The parenchymatous extravisation is sometimes very extensive, at others it is absent, though it will usually be found in the liver, spleen, and in the kidneys. Pulmonary lesions are neither constant, nor necessary. In the early stages the lesions are like those of pleuro pneumonia of an exudative or effusive type. In time the inflammation becomes circumscribed by the effused lymph, the surfaces of the inflamed space becomes raised above the surrounding level. The pleura becomes opaque and thickened, and masses of lymph are deposited on its external surface. On section the diseased lung is found to be solid and friable, charged with serum, red, black or gray, in color, (red, black, or gray hepatization,) increased in density and in specific gravity; decreased in resilience, and separated from the rest of the lung-structure by a distinct segregating band. The bronchial tubes and the trachea are often filled with serum or coagulated lymph. The small intestine shows a condition of hyperaemia or echymesis in the mucus and sub-mucus tissues, and serous coverings, which conditions apply to the stomach; but it is the large intestine which shows the most characteristic appearances. There are smaller or larger, isolated or confluent ulcerations at and around the ileo-caecal valve, the mucus membrane being hyperaemic even to echymosis. The