88 DISEASES OF CATTLE. 



second sound there is a longer interval until tlie first is heard again, 

 which corresponds with the interval, or pause, between the beats of the 

 heart. Opinions differ as to the exact cause of these sounds. The first 

 corresponds with, and is said to be due to, the closure of the auriculo- 

 vcntricular valves ; by some authorities it is thought to be a muscular 

 sound caused by the contraction of the ventricles; others think it is 

 the impulse of the heart against the wall of the chest. The second 

 sound is caused by the closure of the valves at the beginning of the 

 common aorta and pulmonary artery. These sounds, as heard when 

 the ear is placed against the chest, may be said to resemble the pro- 

 nunciation of the words " lub-dup," " lub-dup," " lub-dup," etc. 



To appreciate 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. By having an assistant pull 

 the left fore leg and elbow forward, a better opportunity is afforded to 

 place the ear against the chest in the desired location. If the hand is 

 placed flatly against the chest in the same situation, the beating of the 

 heart will be felt. The impulse of the heart may be felt and the sounds 

 may be heard fairly well in lean cattle, but in fat ones it is difficult and 

 often impossible to detect either impulse or sound with any degree of 

 satisfaction. 



The impulse of the heart, as felt by placing the hand against the 

 chest, is of some consequence in arriving at a conclusion in respect to 

 disease of the heart; but it must be remembered that the impulse may 

 be very much increased by diseases other than those of the heart, as 

 for example, inflammation of various organs, severe pains, etc. The im- 

 pulse may also be increased (when disease does not exist) by work, 

 exercise, fright, or any cause of excitement. 



The variations from the natural heart sounds will be pointed out 

 when the diseases, in which they occur, are described. 



PALPITATION. 



When the impulse of the heart is excessive, that is, when it beats 

 more or less tumultuously, the familiar expression " palpitation of the 

 heart" is applied; and by many it is called " thumps.*' The hand or 

 ear placed against the chest easily detects the unnatural beating. In 

 some cases it is so violent that the motion may be seen at a distance. 

 Palpitation is but the symptom, and in many instances not connected 

 with disease of the structure of the heart or its membranes. An ani- 

 mal badly frightened may have palpitation. When it comes on sud- 

 denly and soon passes away, it depends on some cause other than dis- 

 ease of the heart; but when it is gradually manifested, and becomes 

 constant, although more pronounced at one time than another, heart 

 disease may be suspected, especially if other symptons of heart disease 

 are present. 



