Part 27

2dly. Apart from the importation into countries, we have this certain proof--to which special attention was drawn several years ago--that cattle-dealers' farms, and public markets, constitute the busy centres of infection. Most anxious and careful inquiries have established the proposition that in breeding-districts, where the proprietors of extensive dairies--as in Dumfries, Scotland, and other places--abstain from buying, except from their neighbors, who have never had diseases of the lungs amongst their stock, pleuro-pneumonia has not been seen. There is a wide district in the Vicinity of Abington, England, and in the parish of Crawford, which has not been visited by this plague, with the exception of two farms, into which market-cattle had been imported and thus brought the disease.

3dly. In 1854 appeared a Report of the Researches on Pleuro-Pneumonia, by a scientific commission, instituted by the Minister of Agriculture in France. This very able pamphlet was edited by Prof. Bouley, of Alfort, France. The members of the commission belonged to the most eminent veterinarians and agriculturists in France. Magendie was President; Regnal, Secretary; besides Rayer, the renowned comparative pathologist; Yvart, the Inspector-General of the Imperial Veterinary Schools; Renault, Inspector of the Imperial Veterinary Schools; Delafond, Director of Alfort College; Bouley, Lassaigne, Baudemont, Doyere, Manny de Morny, and a few others representing the public. If such a commission were occasionally appointed in this country for similar purposes, how much light would be thrown on subjects of paramount importance to the agricultural community!

Conclusions arrived at by the commission are too important to be overlooked in this connection. The reader must peruse the Report itself, if he needs to satisfy himself as to the care taken in conducting the investigations: but the foregoing names sufficiently attest the indisputable nature of the facts alluded to.

In instituting its experiments, the commission had in view the solving of the following questions:--

1stly. Is the epizooetic pleuro-pneumonia of cattle susceptible of being transmitted from diseased to healthy animals by cohabitation?

2dly. In the event of such contagion's existing, would all the animals become affected, or what proportion would resist the disease?

3dly. Amongst the animals attacked by the disease, how many recover, and under what circumstances? How many succumb?

4thly. Are there any animals of the ox species decidedly free from any susceptibility of being affected from the contagion of pleuro-pneumonia?

5thly. Do the animals, which have been once affected by a mild form of the disease, enjoy immunity from subsequent attacks?

6thly. Do the animals, which have once been affected by the disease in its active form, enjoy such immunity?

To determine these questions, the commission submitted at different times to the influence of cohabitation with diseased animals forty-six perfectly healthy ones, chosen from districts in which they had never been exposed to a similar influence.

Of these forty-six animals, twenty were experimented on at Pomeraye, two at Charentonneau, thirteen at Alfort, and eleven, in the fourth experiment, at Charentonneau.

Of this number, twenty-one animals resisted the disease when first submitted to the influence of cohabitation, ten suffered slightly, and fifteen took the disease. Of the fifteen affected, four died, and eleven recovered. Consequently, the animals which apparently escaped the disease at the first trial amounted to 45.65 per cent., and those affected to 21.73 per cent. Of these, 23.91 per cent. recovered, and 8.69 per cent. died. But the external appearances in some instances proved deceptive, and six of the eleven animals of the last experiment, which were regarded as having escaped free, were found, on being destroyed, to bear distinct evidence of having been affected. This, therefore, modifies the foregoing calculations, and the numbers should stand thus:--

15 enjoy immunity, or 32.61 per cent. 10 indisposed, " 21.73 " 17 animals cured, " 36.95 " 4 dead, " 8.98 "

Of the forty-two animals which were exposed in the first experiments at Pomeraye and Charentonneau, and which escaped either without becoming affected, or recovering, eighteen were submitted to a second trial; and of these eighteen animals, five had, in the first experiment, suffered from the disease and had recovered; five had now become affected; and four had been indisposed. The four animals submitted to the influence of contagion a third time, had been affected on the occasion of the first trial. None of the eighteen animals contracted the disease during these renewed exposures to the influence of contagion.

From the results of these experiments, the commission drew the following conclusions:--

1stly. The epizooetic pleuro-pneumonia is susceptible of being transmitted from diseased to healthy animals by cohabitation.

2dly. All the animals exposed do not take the disease; some suffer slightly, and others not at all.

3dly. Of the affected animals, some recover and others die.

4thly. The animals, whether slightly or severely affected, possess an immunity against subsequent attacks.

These are the general conclusions which the commission deemed themselves authorized to draw from their experiments. The absolute proportion of animals which become affected, or which escape the disease, or of those which die and which recover, as a general rule, cannot be deduced from the foregoing experiments, which, for such a purpose, are too limited. The commission simply state the numbers resulting from their experiments. From these it transpires that forty five of the animals became severely affected with pleuro-pneumonia, and twenty-one per cent. took the disease slightly, making the whole sixty-six per cent. which were more or less severely attacked. Thirty-four per cent. remained free from any malady. The proportion of animals which re-acquired their wonted appearance of health amounted to eighty-three per cent., whereas seventeen per cent. died. Many minor points might be insisted on, but it is sufficient here to say, that the most careful analysis of all facts has proved to practical veterinarians, as well as to experienced agriculturists, and must prove to all who will calmly and dispassionately consider the point, that pleuro-pneumonia is pre-eminently an infectious, or contagious disease.

Symptoms.--From the time that an animal is exposed to the contagion to the first manifestation of symptoms, a certain period elapses. This is the period of incubation. It varies from a fortnight to forty days, or even several months. The first signs, proving that the animal has been seized, can scarcely be detected by any but a professional man; though, if a proprietor of cattle were extremely careful, and had pains-taking individuals about his stock, he would invariably notice a slight shiver as ushering in the disorder, which for several days, even after the shivering fit, would limit itself to slight interference in breathing, readily detected on auscultation. Perhaps a cough might be noticed, and that the appetite and milk-secretion diminished. The animal becomes costive, and the shivering fits recur. The cough becomes more constant and oppressive; the pulse full and frequent, usually numbering about eighty per minute at first, and rising to upwards of one hundred. The temperature of the body rises, and all the symptoms of acute fever set in. A moan, or grunt, in the early part of the disease indicates a dangerous attack, and the alae nasi (cartilages of the nose) rise spasmodically at each inspiration; the air rushes through the inflamed windpipe and bronchial tubes, so as to produce a loud, coarse respiratory murmur; and the spasmodic action of the abdominal muscles indicates the difficulty the animal also experiences in the act of expiration. Pressure over the intercostal (between the ribs) spaces, and pressing on the spine, induce the pain so characteristic of pleurisy, and a deep moan not infrequently follows such an experiment. The eyes are bloodshot, mouth clammy, skin dry and tightly bound to the subcutaneous textures, and the urine is scanty and high-colored.

Upon auscultation, the characteristic dry, sonorous rale of ordinary bronchitis may be detected along the windpipe, and in the bronchial tubes. A loud sound of this description is, not infrequently, detected at the anterior part of either side of the chest; whilst the respiratory murmur is entirely lost, posteriorly, from consolidation of the lungs. A decided leathery, frictional sound is detected over a considerable portion of the thoracic surface. As the disease advances, and gangrene, with the production of cavities in the lungs, ensues, loud, cavernous rales are heard, which are more or less circumscribed, occasionally attended by a decided metallic noise. When one lobe of the lungs is alone affected, the morbid sounds are confined to one side, and on the healthy side the respiratory murmur is uniformly louder all over.

By carefully auscultating diseased cows from day to day, interesting changes can be discovered during the animal's lifetime. Frequently, the abnormal sounds indicate progressive destruction; but, at other times, portions of the lungs that have been totally impervious to air, become the seat of sibilant rales, and gradually, a healthy respiratory murmur proves that, by absorption of the materials which have been plugging the tissues of the lungs, resolution is fast advancing. Some very remarkable cases of this description have been encountered in practice.

Unfortunately, we often find a rapid destruction of the tissues of the lungs, and speedy dissolution. In other instances, the general symptoms of hectic, or consumption, attend lingering cases, in which the temperature of the body becomes low, and the animal has a dainty appetite, or refuses all nourishment. It has a discharge from the eyes, and a fetid, sanious discharge from the nose. Not infrequently, it coughs up disorganized lung-tissue and putrid pus. Great prostration, and, indeed, typhus symptoms, set in. There is a fetid diarrhoea, and the animal sinks in the most emaciated state, often dying from suffocation, in consequence of the complete destruction of the respiratory structures.

Post mortem appearances.--In acute cases, the cadaverous lesions chiefly consist in abundant false membranes in the trachea, or windpipe, and closure of the bronchial tubes by plastic lymph. The air-vesicles are completely plugged by this material, and very interesting specimens may be obtained by careful dissection, in the shape of casts of the bronchial tubes and air-vesicles, clustered together like bunches of grapes. On slicing the lungs in these cases, hepatization is observed, presenting a very peculiar appearance, which is, in a great measure, due to the arrangement of the lung-tissue in cattle. The pulmonary lobules are of a deep-red or brown color, perfectly consolidated, and intersected or separated, one from the other, by lighter streaks of yellowish-red lymph, occupying the interlobular, areolar tissue. In the more chronic cases, the diseased lobes and lobules are found partly separated from the more healthy structures.

This occurs from gangrene, and putrefactive changes, or in some instances, from the ulcerative process, so constantly observed in the segregation of dead from living tissues. Abscesses are not infrequently found in different parts of the lungs. Sometimes circumscribed, at others connected with bronchial tubes, and not infrequently communicating with the pleural cavity. True empyema is not often seen; but, at all times, the adhesions between the costal and visceral pleura are extensive, and there is much effusion in the chest. In dressed carcasses of cows that have been slaughtered from pleuro-pneumonia, even though the disease has not been far advanced, it will be found that the butcher has carefully scraped the serous membrane off the inner surface of the ribs, as it would otherwise be impossible for him to give the pleura its healthy, smooth aspect, from the firm manner in which the abundant false membranes adhere to it. The diseased lungs sometimes attain inordinate weight. They have been known to weigh as much as sixty pounds.

Treatment.--The veterinary profession is regarded by many who have sustained heavy losses from pleuro-pneumonia, as deeply ignorant, because its members cannot often cure the disease. Persons forget that there are several epidemics which prove equally difficult to manage on the part of the physician, such as cholera, yellow fever, etc. The poison in these contagious, epizooetic diseases is so virulent that the animals may be regarded as dead from the moment they are attacked. Its elimination from the system is impossible, and medicine cannot support an animal through its tardy, exhausting, and destructive process of clearing the system of so potent a virus. All antiphlogistic means have failed, such as blood-letting and the free use of evacuants. Derivatives, in the form of mustard-poultices, or more active blisters, are attended with good results. Stimulants have proved of the greatest service; and the late Prof. Tessona, of Turin, strongly recommended, from the very onset of the disease, the administration of strong doses of quinine. Maffei, of Ferrara, states that he has obtained great benefit from the employment of ferruginous tonics and manganese in the very acute stage of the malady, supported by alcoholic stimulants. Recently, the advantages resulting from the use of sulphate of iron, both as a preventive and curative, have been exhibited in France. It would appear that the most valuable depurative method of treatment yet resorted to is by the careful use of the Roman bath. Acting, like all other sudorifics in cases of fever and blood diseases, it carries off by the skin much of the poison, without unduly lowering the vital powers.