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.
[Illustration: PLATE XXXIV. TUBERCULOSIS OF THE LUNGS OF CATTLE.]
[Illustration: PLATE XXXV. TUBERCULOSIS OF THE LIVER.]
[Illustration: PLATE XXXVI. TUBERCULOSIS OF LYMPH GLAND AND OF
OMENTUM (CAUL).]
[Illustration: PLATE XXXVII. FIG. 1.--TUBERCULOSIS OF SIRLOIN AND
PORTERHOUSE CUTS OF BEEF.
FIG. 2.--TUBERCULOSIS OF PLEURA OF A COW, SO-CALLED "PEARLY
DISEASE."]
[Illustration: PLATE XXXVIII. TUBERCULOSIS OF COW'S UDDER.]
* * * * *
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.
* * * * *
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.
Practically all the animals that react are affected with tuberculosis and
should be separated from the herd, not only in the interest of the public,
but in the interest of the owner of the herd. The best authorities admit,
after studying many thousands of tests, that there are few, if any,
mistakes made in condemning cattle which show a typical tuberculin
reaction. The errors are principally in the other direction--that is, some
tuberculous animals are not discovered by the tuberculin test, but as the
most dangerous of these may be picked out by ordinary clinical examination
this fault of tuberculin is not so serious as it at first sight appears.
This being the case, it should not be necessary to force the tuberculin
test upon owners. They should be anxious to adopt it in their own interests
and for the protection of their patrons. There is to-day no greater danger
to the cattle and hog industries than that which confronts them in the form
of tuberculosis, a disease already widespread and rapidly extending.
Furthermore, in view of the results revealed by numerous tests covering
vast numbers of animals, tuberculin must be considered as harmless for
healthy animals. It has also been clearly demonstrated that tuberculin
interferes in no way with the milking function in healthy cattle; neither
in the quantity of milk nor in butter-fat value has any variation been
detected. The conclusions of some of the best authorities on the subject of
its harmlessness to healthy animals are given below.
Nocard and Leclainche state:
Direct experiments and observations collected by thousands show that the
tuberculin injections have no unfavorable effect. With healthy animals
the system is indifferent to the inoculation; with tuberculous animals it
causes slight changes which are not at all serious.
Bang has written as follows on this question: