Chapter 49

The tubercle formation on the serous membranes covering the lungs and chest wall (Pl. XXXVII, fig. 2), which may go on at the same time with the lung disease or independent of it, has been called "pearly disease," on account of the peculiar appearance of the tubercles. These begin as very minute, grayish nodules, which give the originally smooth, lustrous membrane a roughened appearance. These minute tubercles enlarge, become confluent, and project above the surface of the membrane as wartlike masses, attaining the size of peas. In this stage their attachment to the membrane is by means of delicate fibers. The attachment is loose, so that the tubercle hangs by a short pedicle or neck and may be moved slightly to and fro. Large masses are frequently formed by a coalescence of many tubercles and the secondary formation of the same. These may be found on the lungs, the ribs, and the diaphragm. These tubercles likewise undergo degenerative changes. The center partly softens and partly calcifies into a grayish mortarlike mass, and is gritty. Associated with the formation of tubercles on the pleura, those glands situated back of the center of the lungs between the two main lobes (posterior mediastinal) become greatly enlarged and the center cheesy. (Pl. XXXVI, fig. 1.) They may compress the esophagus and interfere with swallowing. The size attained by these tumors and new growths is well illustrated by the fact that, taken together, they not infrequently weigh from 60 to 80 pounds. The bronchial glands, which in the healthy state are not so large as horse-chestnuts, have been found to attain a weight of more than 10 pounds.

In the abdominal cavity tubercles may be found, both in the organs and on the serous membranes covering them. They are situated usually on the omentum, or caul (see Pl. XXXVI, fig. 2), the diaphragm, and the walls of the abdomen. In the liver large and small tubercular masses are occasionally encountered. (See Pl. XXXV.) The mesenteric glands are occasionally enlarged and tuberculous; likewise the glands near the liver. Tubercles may also develop in the spleen, the kidneys, the uterus and ovaries, and the testicles.

Tubercular affection of the intestines seems to be quite rare, although ulcers of the large intestines have been observed. Nodules may also form under the serous covering of the intestines.

The brain and spinal cord are occasionally found tuberculous. Of 40 cases, Semmer found tuberculosis of the brain in 4. It is not improbable that, owing to the infrequency of exposing the brain and spinal cord, tuberculosis may have escaped the attention of pathologists, and it may be that it is not so uncommon as is generally supposed. The tubercles occur on the membranes of the brain as well as in the substance of the brain itself. They project into the ventricles as masses, varying in size from a pinhead to a hen's egg. They finally lead to various inflammatory changes. Jˆhne has observed numerous small tubercles on the membranes of the spinal cord.

Very rarely tuberculous lesions have been observed in the bones and muscles of the body. Not so rare, however, is the affection of the lymphatic glands embedded in the muscular tissue, and those which can be felt beneath the skin. These are situated at the joints, under the jaw, and along the neck.

Of late tubercular disease of the udder in cows (Pl. XXXVIII) has received considerable attention from sanitarians, owing to the infection of the milk with the virus of tuberculosis. According to those who have given this subject special attention, the udder becomes swollen uniformly and quite firm. This swelling, which is painless, frequently attacks but one quarter, more rarely two, these being usually the hind quarters. The larger milk ducts contain yellowish, cheesy particles, in which are many tubercle bacilli. Later larger nodules can be felt within the udder, which undergo the various changes to which tubercles are subject. The udder may grow very hard to the touch and become very large, weighing in some cases up to 40 pounds. The milk, at first normal, becomes thin and watery after a month or so, and is mixed with flakes and tubercle bacilli.

As regards the frequency of the tuberculous processes in the different organs, the following carefully compiled statistics of the disease in Bavaria and Baden may serve as a guide:

Bavaria: Per cent. Tuberculosis of lungs and serous membranes 41 Tuberculosis of lungs alone 33 Tuberculosis of serous membranes alone (pearly disease) 17 Tuberculosis of other organs 8

Baden: Tuberculosis of lungs alone 21 Tuberculosis of serous membranes alone 28 Both combined 39 Generalized tuberculosis 9 Tuberculosis of the sexual organs alone 3

_Symptoms._--The beginning of the disease usually passes unnoticed, inasmuch as it is very slow and insidious and rarely accompanied with fever. When the lungs are involved a dull, short cough is noticed, which may later on become prolonged, convulsive, and very troublesome to the animal. The cough is more frequent in the morning after movement and drinking. The breathing varies. Only when much of the lung tissue is diseased is it labored and accompanied with active movements of the chest and nostrils. Discharge from the nose is rare or absent. At times, however, when the tubercles have broken down and cavities containing cheesy masses have formed in the lung tissue, or when the air tubes have become filled with cheesy and mucous masses, coughing will dislodge them and cause their discharge. In advanced stages the breath may have a disagreeable odor. Pressure on the chest wall may give rise to pain.

The general effect on the body is at first slight. In fact, animals may remain in good flesh for a considerable time. Invariably as the disease progresses loss of flesh and appetite and paleness of the mucous membranes become manifest. These symptoms are accompanied with a gradual diminution of the milk secretion. The debilitated condition of the animal is also manifested by a staring coat and a tough, dry, harsh skin (hidebound). Digestive disturbances are indicated by tympanites, or distention of the rumen by gas, colic, and diarrhea, alternating with constipation. The animal generally dies from exhaustion after a period of sickness which may last months or even years.

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TUBERCULOSIS. DESCRIPTION OF PLATES.

PLATE XXXIV. Tuberculosis of the lungs of cattle. The upper figure represents a large cheesy mass, surrounded by a capsule of connective tissue, the whole embedded in healthy lung tissue. The lower figure illustrates in section a mass of tubercles which have undergone cheesy degeneration, and some of which are surrounded by dense connective tissue.

PLATE XXXV. Tuberculosis of the liver. A large portion of the lobe represented in the plate has undergone tuberculous changes. Numerous nodules are shown in various stages of the disease, the majority of which, however, contain the yellowish, partly cheesy, partly gritty areas characteristic of advanced tuberculous degeneration. This large mass involves the surface of the liver, and also extends into the liver substance.

PLATE XXXVI. Tuberculosis of lymph gland and of omentum (caul).

Fig. 1. A lymph gland from the region of the thorax behind or above the esophagus, or gullet (posterior, or dorsal, mediastinum). The gland is shown cut through and laid open. It is very much enlarged, and the yellowish cheesy masses which represent tissue undergoing tuberculous changes are well shown on the cut surface.

Fig. 2. Omentum, or caul, resting upon the paunch. The reddish nodules with which the membrane is beset are tubercles, the product of the disease.

PLATE XXXVII. Fig. 1. Tuberculosis of the sirloin and porterhouse cuts of beef. The grapelike tuberculous growths are mainly restricted to the lining membrane of the abdomen.

Fig. 2. Tuberculosis of the pleura of a cow, so-called "pearly disease." Notice the grapelike clusters of tubercular nodules scattered over the lining membrane of the chest (pleura).

PLATE XXXVIII. Tuberculosis of cow's udder. The udder was uniformly swollen and quite firm. Small cheesy foci and yellowish lines of tuberculous material follow the course of the milk ducts. The mucous membrane of the milk cistern (_a_) is ulcerated and covered with yellowish cheesy particles. The supramammary lymphatic gland (_b_) is greatly enlarged and contains many miliary tubercular foci.

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Tuberculosis in the abdominal organs is often signalized by abortion and by abnormal sexual manifestations. When the brain is involved, the disease may cause convulsions, unconsciousness, paralysis, as well as peculiar movements in a circle, oblique position of the head, etc. Lydtin quotes the following description of the disease as taken from a Swiss sanitary order:

A dry, short, interrupted, hoarse cough, which the sick animals manifest, especially in the morning at feeding time, still more after somewhat violent exertion. At first these animals may be full blooded and lay on a considerable amount of fat when well fed. As the disease progresses they grow thin and show more and more those appearances which indicate diseased nutrition, such as a staring, lusterless, disheveled coat; dirty, tense skin, which appears very pale in those regions free from hair. The temperature of the skin is below normal. The loss of fat causes sinking of the eyes in their sockets. They appear swimming in water, and their expression is weak. The cough is more frequent, but never or very rarely accompanied with discharge. The body continues to emaciate, even with plenty of food and a good appetite, so that the quantity of milk is small. At times in the early stages of the disease, still more in the later stages, the diseased animals manifest considerable tenderness when pressure is applied to the front or the sides of the chest by coughing, moaning, etc. Often symptoms are wanting in spite of the existence of the disease.

Lydtin also quotes at length a description of the abnormal sexual desire occasionally observed among cows when affected with this disease.

_Diagnosis._--A disease so varied in its attack upon the different organs of the body and in the extent of the disease process must necessarily lead to mistakes when diagnosis is attempted by ordinary means of examination. It has been confounded with the later stages of pleuropneumonia, with parasitic diseases of the brain, the lungs, the intestines, and with actinomycosis. A careful examination of the lungs by auscultation and percussion enables the expert to locate large tuberculous masses, owing to dullness, loss of respiratory murmur, and abnormal sounds, such as blowing, whistling, and creaking. The majority of cases of tuberculosis in cattle, however, including many in which the lungs are quite seriously involved, can not be detected in this manner.

THE TUBERCULIN TEST.

The tuberculin test, which is marvelously accurate in its indications, has been almost universally adopted for the detection of tuberculosis. Tuberculin is a drug prepared by sterilizing, filtering, and concentrating the liquids in which the tubercle bacillus has been allowed to vegetate. It contains the cooked products of the growth of these bacilli, but no living bacilli; consequently, when this substance is injected under the skin of an animal it is absolutely unable to produce the disease, cause abortion, or otherwise injure the animal. In case the injected animal is normal there is no more effect upon the system than would be expected from the injection of sterile water; however, if the animal is tuberculous, a decided rise of temperature will follow the use of tuberculin by the subcutaneous method. This substance, discovered by Koch, has the effect, when injected into the tissues of a tuberculous animal, of causing a decided rise of temperature or other manifestations while it has no such effect upon animals free from the disease. The value of tuberculin for this purpose was tested during the years 1890 and 1891 by Guttman, Roeckl and Sch¸tz, Bang and Salomonsen, Lydtin, Jˆhne and Siedamgrotzky, Nocard, and many others. It was at once recognized as a most remarkable and accurate method of detecting tuberculosis even in the early stages and when the disease had yet made but little progress. It is now quite generally employed.

The tuberculin test came into existence through the most careful and thorough scientific experimentation.

As a result of its use an accurate diagnosis may be established in more than 90 per cent of the cases tested. The relatively few failures in diagnoses are included among two classes of cattle. The first class contains those that are tuberculous, but which do not react either because of the slight effect of an ordinary-sized dose of tuberculin on an advanced case of the disease with so much natural tuberculin already in the system, or on account of a recent previous test with tuberculin which produces a tolerance to this material, lasting for about six weeks. The second class includes those that are not tuberculous, but which show indications of a reaction as a result of (_a_) advanced pregnancy, (_b_) the excitement of [oe]strum, (_c_) concurrent diseases, as inflammation of the lungs, intestines, uterus, udder, or other parts, abortion, retention of afterbirth, indigestion, etc., (_d_) inclosure in a hot, stuffy stable, especially in summer, or exposure to cold drafts or rains, (_e_) any change in the method of feeding, watering, or stabling of the animal during the test. Notwithstanding all these possibilities of error, the results of thousands of tests show that in less than 3 per cent of the cases tested do these failures actually occur. In the first class the chances of error are decidedly reduced by the skilled veterinarian by making careful physical examination and diagnosing clinically these advanced cases, and by the injection of double or triple doses into all recently tested cattle, with the taking of the after-temperature, beginning two hours following the injection and continuing hourly for 20 hours.

It is therefore apparent that tuberculin should be applied only by or under the direction of a competent veterinarian, capable not only of injecting the tuberculin but also of interpreting the results, and particularly of picking out all clinical cases by physical examination. The latter observation is extremely important and should always be made on every animal tested.

In the second class, where the temperature test is used, errors are avoided by eliminating from the test those cases that are nearing parturition or are in heat or show evidence of the previously mentioned diseases or exhibit temperatures sufficiently high to make them unreliable for use as normal. Where other methods of test are used these conditions do not have an important bearing on the results. In addition, a satisfactory tuberculin must be used; also an accurate thermometer and a reliable syringe, in order that a sufficient dose of tuberculin may be given. Finally, the number of apparent errors of the tuberculin test will be greatly diminished if a careful post-mortem examination is made, giving especial attention to the lymph glands. This low percentage of failures being the case, cattle owners should welcome the tuberculin test, not only for their own interest but for the welfare of the public as well. Where this method of diagnosing the disease has been adopted tuberculosis is gradually being eradicated. Without its use the disease can not be controlled and the owner is confronted with serious and continuous losses; with its use the disease can be eradicated from the herd, a clean herd established in a few years without very serious loss or hardship, and the danger of its spread to man removed. Tuberculin may therefore be considered a most beneficial discovery for the stock raiser.

Law has clearly stated the question when he says--

Many stock owners still entertain an ignorant and unwarranted dread of the tuberculin test. It is true that when recklessly used by ignorant and careless people it may be made a root of evil, yet as employed by the intelligent and careful expert it is not only perfectly safe, but it is the only known means of ascertaining approximately the actual number affected in a given herd. In most infected herds living under what are in other respects good hygienic conditions two-thirds or three-fourths are not to be detected without its aid, so that in clearing a herd from tuberculosis and placing both herd and products above suspicion the test becomes essential. * * * In skilled hands the tuberculin test will show at least nine-tenths of all cases of tuberculosis when other methods of diagnosis will not detect one-tenth.

Probably the most popular objection to tuberculin is that it is too searching, since it discovers cases in which the lesions are small and obscure. While this fact is admitted, it should also be remembered that such a small lesion to-day may break down and become widely disseminated in a relatively short period. Therefore any cow affected with tuberculosis, even to a slight degree, must be considered as dangerous not only to the other animals in the herd but also to the consumer of her products.

In 1898 Bang, of Copenhagen, one of the highest European authorities, in his paper presented to the Congress for the Study of Human and Animal Tuberculosis, at Paris, said:

Numerous tests made in almost every civilized country have demonstrated that in the majority of cases tuberculin is an excellent means for diagnosing the existence or nonexistence of the disease, but giving us no positive information as to the extent to which the disease has progressed. When tuberculin produces a typical reaction we may be almost sure that there exists in the body of the animal a tubercular process. The cases in which a careful examiner has not succeeded in finding it are very rare, and I am led to believe that when, notwithstanding all the pains taken, it has escaped discovery, the reason is that it is located in a portion of the body that is particularly inaccessible. Nevertheless, it is not to be denied that a fever, entirely accidental and of short duration, may in some rare cases have simulated a reaction. However this may be, the error committed in wrongly condemning an occasional animal for tuberculosis is of no practical consequence.

A worse aspect of the case is that there are some diseased animals in which tuberculin fails to discover the existence of tuberculosis. In most of these, no doubt, the deposits are old, insignificant, and generally calcified, or they are cases where the disease is arrested and perhaps in process of recovery, and which are possibly incapable of disseminating the contagion. But it is known that there are cases, not altogether rare, where tuberculin fails to cause a reaction in a highly tuberculous animal, and consequently one in which the disease exists in an extremely contagious form. For this reason a clinical examination should always be made of an animal which does not give a reaction but which shows symptoms indicating that, notwithstanding the test, it may suffer from tuberculosis.

Nocard, of Paris, wrote also in 1898 as follows:

The degree of certainty of the indications furnished may be stated in precise terms. _The observation of a clear reaction to tuberculin is unequivocal; the animal is tuberculous._ The pretended errors imputed to the method are explained by the extreme sensitiveness of the reagent, which is capable of detecting the smallest lesion. It often requires prolonged and minute researches in the depths of all the tissues to discover the few miliary centers, the presence of which has been revealed. The reaction is absolutely specific. In those cases where it is observed with animals which show lesions of another disease (actinomycosis, hydatid disease, verminous bronchitis, distomatosis), it may be affirmed that there exists, in addition to these conspicuous changes, a tuberculous center which alone has provoked the reaction.

_The failure to react does not necessarily imply absence of tuberculosis._ Such failures of tuberculin are very exceptional. They are seen most frequently with animals affected with tuberculosis in a very advanced stage and made evident by plain external signs. Sometimes, also, there are found at the post-mortem examination of animals which have not reacted small fibrous or calcified lesions in such a condition that one is tempted to believe them cured. Whether sterile or not, these lesions have no tendency to increase, and they are not very dangerous from the point of view of contagion.

These opinions of two eminent authorities, living in different countries, after long experience of their own and after studying the results of the many tests made in different parts of the world, should have great weight. They are essentially the same throughout.

In 1897 Voges compiled statistics of tuberculin tests, the accuracy of which had been determined by post-mortem examination. Of 7,327 animals tested, it appeared that errors had been made with 204, or 2.78 per cent. In the work of the Pennsylvania Live Stock Sanitary Board post-mortem examinations were made on about 4,400 reacting cattle and the disease was found in all but 8 of those which had given characteristic reactions.

The results of a much larger number of tests might be compiled at this time, but they would not materially change the average of those already mentioned. It is plain that tuberculin is a remarkably accurate test of tuberculosis, that the animals which react may be safely considered as tuberculous, and that when a careful clinical examination is practiced in addition to the test there are few animals in a dangerous condition which escape detection.

The first questions asked by those who oppose the adoption of the tuberculin tests are: Is this test infallible? and, if it is not infallible, why should it be forced upon the cattle owners of the country?

In answer to these questions it may be said that tuberculin is not absolutely infallible, and yet it is by far the best method of diagnosing tuberculosis that has been discovered. It is much better than any test known for pleuropneumonia when that disease was eradicated.