only after somewhat prolonged feeding. The condition is one of cumulative
poisoning, and animals sometimes decline very rapidly after the first
symptoms appear. In many cases animals acquire a habit of eating loco and
prefer it to any other feed. The poison affects the central nervous system.
There is a lack of muscular coordination and the animal performs very
erratic movements. In the later stages the animal becomes emaciated and
eventually dies of starvation.
_Treatment._--Locoed animals are badly constipated, and it is important
that this condition should be remedied at the start. Any purgative can be
used, but Epsom salt has been found especially effective. If locoed animals
can be turned into a field of alfalfa, a large proportion of them will
recover with no further treatment. Recovery may be aided by giving cattle,
hypodermically, daily doses of three-twentieths to four-twentieths of a
grain of strychnin. By this treatment cattle can be cured and put in
condition for market.
WHITE SNAKEROOT (EUPATORIUM URTIC∆FOLIUM).
White snakeroot, frequently known as "rich weed," is a plant growing in
great abundance in some of the eastern and central regions of the United
States. It is particularly abundant in parts of Ohio, Indiana, and
Illinois, and in western North Carolina. It is responsible for most, if not
all, of the cases of a disease which is commonly known as "milk sickness."
_Symptoms._--The animals are constipated, sometimes have bloody feces,
become weak, and exhibit muscular trembling. This trembling is very
characteristic, so that the disease is sometimes known as "the trembles."
_Remedy._--There are no remedies which will work very efficiently. It is
desirable to give the animals purgatives like Epsom salt and, of course, to
remove them from fields where this plant is abundant.
RAYLESS GOLDENROD (ISOCOMA WRIGHTII).
The rayless goldenrod is a plant growing in especial abundance in parts of
the Pecos Valley in New Mexico and Arizona, and there produces a disease so
much like that produced in the East by white snakeroot that it is sometimes
called milk sickness. More generally this disease goes under the name of
"alkali disease." The plant has produced heavy losses in the regions where
it grows abundantly.
_Symptoms._--The symptoms are much like those produced by the white
snakeroot. The animals are constipated, sometimes have bloody feces, become
weak, and exhibit muscular trembling. There is good reason to think, too,
that the milk of cows eating this plant is more or less injurious.
_Treatment._--A purgative like Epsom salt will aid an animal in recovering,
but most important is to remove the cattle from pastures where the plant is
abundant and give them an abundance of good forage. Under such conditions
they are almost certain to recover.
MILKWEEDS.
Many of the milkweeds have long been known to have more or less poisonous
properties. Within the last few years it has been discovered that certain
of the milkweeds going under the popular name of whorled milkweeds are
especially toxic. There are at least four species of whorled milkweeds, but
two of them are particularly important from the standpoint of people
handling livestock. One, known scientifically as _Asclepias galioides_, is
harmful in Colorado, Utah, Arizona, and New Mexico, while another, known as
_Asclepias mexicana_, has produced losses, especially in California and
Nevada. These whorled milkweeds are distasteful to all animals and are
eaten only when the stock is closely confined to pastures where there is
little else in the way of forage.
_Symptoms._--The most prominent symptoms are weakness, producing
staggering, and this is followed in acute cases by violent spasms.
_Treatment._--There is no treatment which will effectively antidote the
effect of the poison. In practically all cases, however, poisoning may be
avoided if care is taken to prevent animals from being closely confined
where this plant is abundant, as they never eat the plant by choice.
CHERRY.
In the leaves of the cherries more or less hydrocyanic acid is produced,
and when these leaves are eaten in any considerable quantity cases of
poisoning are likely to arise. It is popularly supposed that these cases
arise from eating wilted cherry leaves, but there is every reason to think
that the fresh leaves will produce the same results. These cases are easily
prevented, because no harm results from eating a small quantity of the
leaves, and if the fact is recognized that poisoning may result from eating
a large quantity, it is not difficult to care for the animals so as to
prevent poisoning.
ERGOTISM.
The poisonous effects of ergot (Pls. V, VI) appear chiefly in the winter
and spring of the year and among cattle. It is developed among grasses
grown on rich soil in hot, damp seasons. Rye seems more liable to ergot
than any of our other crops. Of the grasses which enter into the
composition of hay, bluegrass is the most likely to become affected. Ergot
may also affect redtop, oats, grasses, and grains. On the plant the fungus
manifests itself on the seeds, where it is easily recognized when the hay
is examined in the mow. The ergotized seeds are several times larger than
the natural seeds--hard, black, and generally curved in shape.
The effect of the protracted use of ergot in the feed is pretty well
understood to be that of producing a degeneration and obstruction of the
smaller arterial branches. The result is to shut off the blood supply to
the distal parts of the body, where the circulation is weakest, and thus to
produce a mummification or dry gangrene of the extremities, as the ears,
tail, feet, etc. Cattle seem to be more susceptible than other animals to
the influence of ergot, possibly on account of the slowness of the heart's
action. When the effect of the poison has become sufficient to entirely
arrest the circulation in any part, the structures soon die. The disorder
manifests itself as lameness in one or more limbs; swelling about the ankle
which may result in only a small slough or the loss of a toe, but it may
circumscribe the limb at any point below the knee or hock by an indented
ring below which the tissues become dead. The indentation soon changes to a
crack, which extends completely around the limb, forming the line of
separation between the dead and living structures. The crack deepens till
the parts below drop off without loss of blood, and frequently with very
little pus. Ergot may cause serious irritation of the digestive tract, or
by acting upon the nervous system it may cause lethargy or paralysis. It
also operates to cause contraction of the uterus, and may thus cause
abortion.
_Treatment._--Regarding the treatment, change of feed and local antiseptics
are, of course, indicated. The former may be useful as a preventive, but
when the symptoms have appeared the animal is necessarily so completely
saturated that recovery is likely to be tedious. Tannin may be given
internally in doses of one-half dram twice daily for a few days to
neutralize the unabsorbed alkaloids of the ergot. At the same time give
castor oil. To dilate the blood vessels give chloral hydrate. Bathe the
affected parts with hot water. If sloughing has gone far, amputation must
be resorted to.
OTHER POISONOUS FUNGI.
Many other fungi poison herbivora. In some instances, however, where fungi
are blamed for causing disease their presence on the feedstuff or herbage
is but coincidental with some other and more potent disease-producing
factor. For example, if the conditions are favorable to the growth of fungi
they are also favorable to the growth of bacteria, and bacteria may produce
poisons in feeds. In general it may be said that any feed that is moldy,
musty, or putrid is possibly dangerous. Silage, properly cured, does not
belong to this class, because the curing of silage is not a bacterial
process. But spoiled silage and silage matted with mold is dangerous and
should not be fed.
POISONING BY ANIMAL PRODUCTS.
SNAKE BITES.
The poison contained in the tooth glands of certain venomous reptiles,
particularly some of the snakes, which is injected into or under the skin
of an animal bitten by the reptile, is a very powerful agent. It is likely
to produce a serious local irritation, and in the case of the more
poisonous snakes serious constitutional disturbances, even to causing
death, which it may do in either of two ways: First, when very strong, by
exerting a narcotic influence similar to that of some of the powerful
poisons, checking heart action. Second, by diffused inflammation of the
areolar tissue, gangrene, and extensive sloughing.
_Symptoms._--The symptoms of snake bite are a local swelling caused by an
intense local inflammation, pricks showing where the fangs penetrated,
depression, weakness, feeble pulse, difficult breathing, bluish
discoloration of the visible mucous membranes, stupor, or convulsions. If
the poison is not powerful or plentiful enough to produce death, it is, at
any rate, likely to cause severe local abscesses or sloughs.
_Treatment._--The treatment may be divided into local and general. Locally
every effort should be made to prevent absorption of the poison. If
discovered at once the bitten part had better be excised. If that is
impracticable and a ligature can be applied, as in the case of a bite to
one of the limbs, no time should be lost in applying it above the injury.
It should be made sufficiently tight to so far as possible arrest
circulation in the bitten part. The wound should be freely incised, so that
it will bleed freely, and the poison should be extracted by cupping, or
pressed out by squeezing with the fingers. Permanganate of potassium in 5
per cent solution should be applied to and injected into the wound. The
depressing effect of the poison on the general system should be
counteracted by hypodermic injections of strychnin, or by liberal drenching
with stimulants, such as coffee, digitalis, or the aromatic spirits or
carbonate of ammonia. In animal practice the alcoholic stimulants and local
treatment above described are likely to meet with best success. A special
antitoxin for use in treating snake bite is now prepared and may be had
from the leading druggists. It is quite effective if used promptly.
WASP AND BEE STINGS.
Wasps and bees secrete a poisonous substance which they are able to insert
through the skin of an animal by the aid of their sharp stings. This poison
is a severe local irritant and may even cause local gangrene. It also has a
depressing effect upon the central nervous system and destroys the
red-blood corpuscles. To produce these general effects it must be
introduced in very large quantities, as when an animal is stung by a swarm
of bees or wasps.
_Treatment._--The treatment is to wash the parts with diluted ammonia or
permanganate of potassium solution and to give stimulants internally. If
there is so much swelling about the head and nostrils as to interfere with
breathing, tracheotomy may be necessary.
POISONING WITH SPANISH FLY.
Spanish fly, in the form of powdered cantharides, may be given in an
overdose, or when applied as a blister to too large a surface of skin
enough may be absorbed to poison. If given by the mouth, it causes severe
irritation of the gastrointestinal tract, shown by salivation, sore throat,
colic, bloody diarrhea, etc. It also produces, whether given by the mouth
or absorbed through the skin, irritation of the urinary tract, as shown by
frequent and painful urination. If death results, it is due to respiratory
paralysis.
_Treatment._--Give protectives and the white of egg, with opium. Do not
give oils or alcohol.
DISEASES OF THE HEART, BLOOD VESSELS, AND
LYMPHATICS.
By W. H. HARBAUGH, V. S.
[Revised by Leonard Pearson, B. S., V. M. D.]
THE CIRCULATORY SYSTEM.
In cattle, as in human beings, the heart, blood vessels, and lymphatics may
be described as the circulatory apparatus.
The heart is in the thoracic cavity (chest). It is conical in form, with
the base or large part uppermost, while the apex, or point, rests just
above the sternum (breastbone). It is situated between the right and left
lungs, the apex inclining to the left, and owing to this the heart beats
are best felt on the left side of the chest, behind the elbow. The heart
may be considered as a hollow muscle, containing four compartments, two on
each side. The upper compartments are called auricles and the lower ones
ventricles. The right auricle and ventricle are completely separated from
the left auricle and ventricle by a thick septum or wall, so that there is
no communication between the right and left sides of the organ.
At the bottom of each auricle is the auriculo-ventricular opening, each
provided with a valve to close it when the heart contracts to force the
blood into the arteries. In the interval between the contractions these
valves hang down into the ventricles.
The muscular tissue of the heart belongs to that class known as
involuntary, because its action is not controlled by the will.
The cavities of the heart are lined by a serous membrane, called the
endocardium, which may be considered as a continuation of the veins and the
arteries, forming their internal lining. The walls of the ventricles are
thicker than those of the auricles, and the walls of the left ventricle are
much thicker than those of the right.
The heart is enveloped by a fibrous sac (or bag), called the pericardium,
which assumes much of the general shape of the outer surface of the heart.
The action of the heart is similar to that of a pump and its function is to
keep the blood in circulation. The auricles may be considered as the
reservoirs or receivers of the blood and the ventricles as the pump
chambers. During the interval between contractions, the heart being in
momentary repose, the blood pours into the auricles from the veins; the
auriculo-ventricular orifices being widely open, the ventricles also
receive blood; the auricles contract and the ventricles are filled;
contraction of the ventricles follows; the auriculo-ventricular valves are
forced up by the pressure of the blood and close the auriculo-ventricular
openings and prevent the return of blood into the auricles; the contraction
of the ventricles forces the blood from the right ventricle into the lungs
through the pulmonary artery and its branches, and from the left ventricle
into the aorta, thence through the arteries to all parts of the body. After
the contraction of the ventricles the heart is again in momentary repose
and is being filled with blood, while the valves in the aorta and pulmonary
artery close to prevent the return of blood into the ventricles. (See Pl.
VII.)
The average weight of the heart of an ox is said to be from 3-1/2 to 5
pounds; but, of course, owing to the many breeds and sizes of cattle, it
must vary in different animals.
The vessels that convey the blood from the heart to all parts of the body
are called arteries; those which return the blood to the heart are called
veins. The arteries divide and subdivide (like the branches of a tree),
become smaller and smaller, and ultimately ramify into every part of the
body. Between the ultimate ramifications of the arteries and the beginning
of the veins there is an intermediate system of very minute vessels called
capillaries, which connect the arterial with the venous system of the
circulation. The walls of the arteries are possessed of a certain amount of
rigidity, sufficient to keep the tubes open when they are empty.
The blood leaves the left ventricle through a single vessel, the common
aorta, consisting of the anterior and posterior aortas, which give off the
large arteries.
The veins take the blood from the capillaries in all parts of the body.
They begin in very small tubes, which unite to become larger in size and
less in number as they approach the heart.
In its course an artery is usually accompanied with a vein and in many
situations with a nerve. The more important arteries are placed deep within
the body; when they are superficial, however, they are generally found
where least exposed to injury, as, for example, on the inner side of the
legs. Arteries are less numerous than veins, and their total capacity is
much less than that of the veins. A great number of veins are in the tissue
immediately beneath the skin and do not generally accompany arteries.
The blood, throughout its course in the heart, arteries, capillaries, and
veins, is inclosed within these vessels. Except where the large lymphatics
empty into the venous blood, there is no opening into the course of the
blood.
All the arteries except the pulmonary and its branches carry bright-red
blood, and all the veins, except the pulmonary veins, carry dark-red blood.
The impure dark-red blood is collected from the capillary vessels and
carried to the right auricle by the veins; it passes down into the right
ventricle, and thence into the pulmonary artery and through its branches to
the capillaries of the lungs, where the carbonic-acid gas and other
impurities are given up to the air in the air cells of the lungs (through
the thin walls between the capillaries and the air cells), and where it
also absorbs from the air the oxygen gas necessary to sustain life. This
gas changes it to the bright-red, pure blood. It passes from the
capillaries to the branches of the pulmonary veins, which convey it to the
left auricle of the heart; it then passes through the auriculo-ventricular
opening into the left ventricle, the contraction of which forces it through
the common aorta into the posterior and anterior aortas, and through all
the arteries of the body into the capillaries, where it parts with its
oxygen and nutritive elements and where it absorbs carbonic-acid gas and
becomes dark colored. (See theoretical diagram of the circulation, Pl.
VII.)
The branches of certain arteries in different parts unite again after
subdividing. This reuniting is called anastomosing, and assures a quota of
blood to a part if one of the anastomosing arteries should be tied in case
of hemorrhage, or should be destroyed by accident or operation.
THE BLOOD.
The various kinds of food, after being digested in the alimentary canal,
are absorbed and carried into the blood by the lymphatics, and by the blood
to the places where nutrition is required. The blood takes from all parts
of the body all that is no longer required, and carries it to the different
organs through which it is eliminated from the body. It contains within
itself all the elements which nourish the body.
The blood may be considered as a fluid holding in solution certain
inorganic elements and having certain bodies suspended in it. To facilitate
description, the blood may be considered as made up of the corpuscles and
the liquor sanguinis. The corpuscles are of two kinds, the red and the
white, the red being the more numerous. The color of the blood is caused by
the coloring matter in the red corpuscles, which are the oxygen carriers.
Both kinds are very minute bodies, which require the aid of the microscope
to recognize them. The liquor sanguinis is composed of water containing in
solution salts, albumen, and the elements of fibrin.
The lymphatics, or absorbents, are the vessels which carry the lymph and
chyle in the blood. They begin as capillaries in all parts of the body,
gradually uniting to form larger trunks. Placed along the course of the
lymphatic vessels are glands, in some situations collected into groups; for
example, in the groin. These glands are often involved in inflammation
arising from the absorption of deleterious matter.
Absorption is the function of the lymphatics. The liquor sanguinis passes
from the blood capillaries to supply nutrition to the tissues. All of the
liquor sanguinis that is not required is absorbed by the lymphatic vessels
and conveyed back to the blood by the lymphatic ducts. The lymphatics which
proceed from the intestines convey the chyle into the blood during
digestion. As a rule, the lymphatic vessels follow the course of the veins.
All the absorbent vessels convey their contents to the thoracic duct and
right great lymphatic vein, which empty into the anterior vena cava, where
the lymph and chyle mix with the venous blood, and thus maintain the supply
of nutritive elements in the blood.
THE PULSE.
As fully explained, the heart pumps the blood throughout the arterial
system. The arteries are always full and each contraction of the ventricle
pumps more blood into them; this distends their elastic walls and sends
along them a wave which gradually becomes less perceptible as it nears the
very small arteries. This wave constitutes the pulse, and is lost before
the capillaries are reached. The sensation or impression given to the
finger when placed upon the artery shows the force exerted by the heart and
some important facts concerning the condition of the circulation. In adult
cattle the average number of pulsations in a minute is from 50 to 60. The
pulse is faster than normal after exercise, excitement, on hot days, from
pain, and as a result of fullness of the stomach. In old animals it is
slower than in the young and in males slightly slower than in females. In
fevers and inflammations and in local diseases of the heart the pulse rate
is increased. If the rate is greater than 100 or 110 to the minute the
outlook for recovery is not good.
Other variations of the pulse are known as infrequent pulse, which means
that the number of pulsations in a given time is less than normal. The
irregular or the intermittent pulse is when the pulsations do not follow in
regular order. The large pulse and the small pulse refer to the volume of
the pulse, which may be larger or smaller than usual. The strong pulse and
the feeble pulse refer to the strength or weakness of the pulsation. The
pulse is said to be hard when the vessel feels hard and incompressible, the
soft pulse being the opposite. By dicrotic pulse is meant that kind of
pulsation which makes each beat seem double, and therefore it is generally
called the double pulse.
The venous or "jugular pulse" is the pulsation so frequently observed in
the jugular vein of cattle and is particularly noticeable while they are
ruminating--"chewing the cud." It is not always associated with disease,
but may be a symptom of some disease of the heart; in such cases the
jugular pulse is continuous.
The place selected for feeling the pulse in cattle is where the
submaxillary artery winds around the lower jawbones, just at the lower edge
of the flat muscle on the side of the cheek; or, if the cow is lying down,
the metacarpal artery on the back part of the fore fetlock is very
convenient for the purpose.
THE EXAMINATION OF THE HEART.
Corresponding to the beats of the heart two sounds are emitted which are of
a definite type in healthy animals. The first is produced by the
contraction of the heart and the flow of blood out of it; the second is
caused by the rebound of blood in the aorta and the closure of the valves
that prevent it from flowing backward into the heart, whence it came. The
first sound is the longer and louder of the two, though of low pitch. The
second sound is sharper and shorter, and is not always easy to hear. There
is a brief interval between them.
To distinguish these sounds, the ear is placed against the left side of the
chest, a little above the point where the elbow rests when the animal is
standing in a natural position, and about opposite the sixth rib. Both
heart sounds are reduced in intensity when the animal is weak or when the
heart is forced away from the chest wall by collections of fluid or by
tubercular or other growths. Nonrhythmical heart sound is often caused by
pericarditis or by disease of the valves. It may also be attributable to
overfilling of the heart upon the right side, as occurs in severe
congestion of the lungs and in some febrile diseases.
In pericarditis, sounds like scraping, rubbing, or splashing may be heard,
entirely apart from the two normal sounds above described.