DISEASES OF THE HEART IN DOMESTIC ANIMALS. 
503 
sensible pains. That, however, such cases of momentary attacks 
of the heart actually occur is scarcely to be doubted. As they 
generally pass away without any injurious consequences, they 
are often overlooked; but when they are intense and protracted 
they may be mistaken for dyspnoe. 
II.— Syncope. 
Momentary faintness is often observed, especially in the horse. 
The animal falls down and remains motionless for a few seconds. 
In midsummer such attacks also occur quite frequently in the pas¬ 
ture. Sometimes the prostration lasts a considerable time, from 
3 to 10 minutes. Gradually the animal recovers, the pulse is 
very weak, scarcely perceptible, the heart-beat slow, indistinct, we 
might say fatigued; the sounds and murmurs, with the exception 
of the blood-flowing of the blood, show no other perceptible ab¬ 
normities. The whole mechanism of the heart can be compared 
to a steam engine which works with full power and by a sudden 
closure of the throttle-valve becomes inactive. The cause of such 
conditions is a morbid irritability of the inhibitory nerves. This 
condition, and one similar, can be artificially generated by those 
narcotics and opiates which affect the inhibitory nerves partly 
directly, partly by reflection or by paralysis of the vaso-motor and 
excito nerves. 
III.— Palpitation of the Heart. 
An abnormal excitement of those nerve-elements which regu¬ 
late the rythmical action, appears more frequently and is of more 
importance than the above described condition, and a relaxa'ion 
of the inhibitory nerves is present at the same time. The action 
of the heart is increased, often violent, thus producing a condition 
which is designated palpitation of the heart. Therefore palpita¬ 
tion of the heart is an increased irritability of the heart which 
arises either from a simple functional or organic abnormity. In 
the first case the normal state of the heart is easily established 
during the intervals, whereby we are convinced that the affection 
is purely functional, but the existence of organic changes is in 
this case to be regarded as the exciting cause of the functional 
affection. 
