DISEASES OF THE CIRCULATORY ORGANS
GENERAL DISCUSSION.--The circulatory organs are the heart, arteries, veins
and lymphatics. The _heart_ is the central organ of the circulatory system
(Fig. 23). Its function is to force the blood through the blood-vessels. It
is situated in the thoracic cavity between the lungs, and enclosed by a
special fold of the pleura, the pericardial sack. There are two kinds of
blood-vessels, arteries and veins. The _arteries_ leave the heart and carry
the blood to the many different organs of the body. The _veins_ return to
the heart and carry the blood from the body tissues. The _capillaries_ are
small blood-vessels, microscopic in size, that connect the arteries with
the veins. The arteries carry the pure blood. The opposite is true,
however, of the lesser or pulmonary system. The pulmonary artery carries
the impure blood to the lungs, and the pulmonary veins carry the pure blood
back from the lungs. The _lymphatic vessels_ carry a transparent or
slightly colored fluid and chyle from the tissues and alimentary canal.
This system of vessels empties into the venous system.
[Illustration: FIG. 23.--Photograph of model of horse's heart: auricle;
ventricle; pulmonary artery; pulmonary veins; posterior aorta; and anterior
aorta.]
_The functions of the blood_ are to nourish the body tissues; furnish
material for the purpose of the body secretions; supply the cells of the
body with oxygen; convey from the tissues injurious substances produced by
the cellular activity; and destroy organisms that may have entered the body
tissues. The cellular and fluid portions of the blood are not always
destructive to disease-producing organisms. In certain infectious diseases,
the fluid portion of the blood may contain innumerable organisms, and
destruction of the blood cells occurs.
_In inflammation_ of tissue the circulation of the blood in the inflamed
part undergoes certain characteristic changes. At the beginning there is an
increase in the blood going to the part. This is followed by a slowing of
the blood stream in the small vessels, and the collecting of the blood
cells in the capillaries and veins. These circulatory changes are followed
by the migration of the blood cells, and the escape of the fluid portion of
the blood into the surrounding tissue. The character of the above
circulatory changes depends on the extent of the injury to the tissue.
PALPITATION.--This disturbance in domestic animals seems to be purely
functional. It may occur independent of any organic heart disease. A highly
nervous condition, excitement, over-exertion, debility from disease and the
feeding of an improper ration are the common causes.
The heart beats are so violent and tumultuous as to shake the body, and be
noticed when standing near the animal. The heart sounds are louder than
normal and the pulse beats small and irregular. It may be differentiated
from spasm of the diaphragm by determining the relationship of the heart
beats to the abrupt shocks observed in the costal and flank regions.
_The treatment_ consists in keeping the animal quiet and avoiding any
excitement. A quiet stall away from the other animals is best. The
treatment of palpitation resulting from some organic heart disease must be
directed largely at the original disease. Morphine is commonly used for the
treatment of this disorder. Weak, anaemic animals should receive blood and
bitter tonics. If we have reason to believe that the disturbance is caused
by improper feeding, the animal should receive a spare diet for a few days.
In such cases it is advisable to administer a physic.
PERICARDITIS.--Inflammation of the pericardial sack is usually a secondary
disease. It is frequently met with in influenza, contagious
pleuropneumonia, hog-cholera and rheumatism. Cattle may suffer from
traumatic pericarditis caused by sharp, pointed, foreign bodies passing
through the wall of the reticulum and penetrating the pericardial sack. The
jagged ends of fractured ribs may cause extensive injury to neighboring
parts, and the inflammation spreads to the pericardial sack.
_The symptoms_ of pericarditis may not be recognized at the very beginning
when the disease occurs as a complication of influenza, or infectious
pleuropneumonia. The manifestation of pain by moving about in the stall,
refusing to eat and the anxious expression of the face are the first
symptoms that the attendant may notice. The body temperature is higher than
normal, and the pulse rapid and irregular. On auscultation, friction sounds
that correspond to the tumultuous beats of the heart are heard. When fluid
collects within the pericardial sack, the heart beats become feeble and the
pulse weak. Labored breathing and bluish discoloration of the lips follow.
The disease usually runs a very acute course. The prognosis is unfavorable.
_The treatment_ recommended in pneumonia is indicated in this disease.
Absolute rest and the feeding of an easily digested, laxative diet is a
very essential part of the treatment. At the very beginning morphine may be
given to quiet the tumultuous beats of the heart. Cold applications to the
chest wall in the form of ice packs should be used. Heart tonics and
stimulants such as digitalis, strychnine and alcohol should be administered
when the pulse beats weaken. To promote absorption of the exudate, iodide
of sodium may be given. Mustard paste, or a cantharides blister applied
over the region of the heart is useful in easing the pain and overcoming
the inflammation. If fluid collects in sufficient quantity to seriously
interfere with the heart action, the sack may be punctured with the trocar
and cannula and the fluid withdrawn. Great care must be used to avoid
injury to the heart and infection of the part.
[Illustration: FIG. 24.--Elephantiasis in horse.]
ACUTE LYMPHANGITIS.--This is an inflammation of the lymphatic vessels of
one or both hind limbs. The attack comes on suddenly and usually occurs in
connection with rest, and in horses that are of slow, quiet temperament.
The _exciting cause_ is an infection of the part with bacteria, the
infection probably occurring through some abrasion or small wound in the
skin.
_The local symptoms_ are swelling, tenderness and lameness in the affected
limb. The animal may refuse to support its weight on the affected limb. The
lymphatic glands in the region are swollen, and the swelling of the limb
pits on pressure. In the chronic form of the disease, the regions of the
cannon and foot remain permanently enlarged, and the swelling is more firm
than it is in the acute form (Fig. 24).
_The general symptoms_ are high body temperature, rapid pulse and the
partial or complete loss of appetite.
_The following treatment_ is recommended: Exercise is indicated in cases
that are not sufficiently advanced to cause severe lameness, or inability
to use the limb; rest and the application of woollen bandages wrung out of
a hot water solution of liquor cresolis compound are recommended; Epsom
salts in one-half pound doses may be given and repeated in two or three
days; a very light diet of soft feed should be given; liniments should
_not_ be applied until the soreness in the limb has subsided; iodide of
potassium may be given twice daily with the feed.
QUESTIONS
1. What are the functions of the blood and lymph?
2. State the changes occurring in the circulation in inflamed tissue.
3. What is palpitation? Give the causes and treatment.
4. What are the common causes of pericarditis?
5. Give the causes and treatment of acute lymphangitis.