In the chronic forms of the disease however a particular class of symptoms usually point towards the organ affected. In cattle, sheep and pigs raised only for slaughter, and as far as possible protected against active exertion, serious heart diseases may exist for a length of time without making themselves manifest by any prominent symptoms. Thus in cows, pins and other sharp pointed bodies swallowed with the food frequently make their way to the heart and lodge for a length of time in its vicinity without material derangement and when at last the animal dies a sudden death they are found transfixing the walls of that organ. In the horse or other animal subjected to exertion the symptoms are usually very patent.
When the heart is enlarged the pulse strong and the circulation full and free, apoplexies or hemorrhages especially on the brain or other soft organs where the resistance is least, are liable to occur. When on the other hand the circulation is weak from atrophy or fatty degeneration of the heart, or from insufficiency of the valves there is a tendency to coldness of the extremities, and to passive congestions with their consequences:—serous effusions, dropsies, and difficult breathing. The imperfect supply of blood to the muscles of the extremities sometimes brings about an unsteadiness of gait in the hind limbs when the animal is trotted for a short distance and sometimes cramps supervene.
Continued coldness of the limbs, and a filling or thickening first of the hind limbs then of the fore and lastly of the chest and belly and of the skin beneath their dependent parts are useful indications.
Shortness of breath and inability to proceed when trotted or galloped on hard ground or when walked up hill, the animal being in fair condition, without fever or cough, but subject to cold extremities and a venous pulse in the jugulars, almost certainly indicates insufficiency of the auriculo-ventricular valves on the right side of the heart.
Vertigo megrims or giddiness may be caused by heart disease. The horse without having sustained any pressure on the veins of the neck by the collar, and having had no previous symptom of brain disease suddenly reels in harness and perhaps falls. There are the cold and engorged limbs or a tendency to their engorgement as in the former case. The attacks recur, when the horse is put to the same exertion, and he proves utterly worthless. In such cases a careful examination of the pulse and heart sounds will complete the chain of evidence.
An almost constant feature of chronic heart disease is a condition of dulness, sluggishness, and in many cases, curiously enough, a tendency to lay on fat, so that although the patient is unfit to work, he appears to enjoy excellent general health to which a period is only put by sudden death.
Affections of the heart are primarily divisible into functional and structural disorders.
PALPITATIONS.
Convulsive contraction of the heart, functional or structural diagnostic features of these. Significance of the functional disorder, genera most liable. Treatment, quiet, heart tonic, digitalis, correct other disorders.
These consist in a sudden violent and convulsive beating of the heart, not connected with any appreciable structural disease. They differ chiefly from the palpitations of organic disease of the heart in the absence of any apparent local change to account for their occurrence. The following table from Bellingham furnishes a number of criteria equally valuable in the lower animals as in man.