DISEASES OF THE HEART IN DOMESTIC ANIMALS. 
501 
cardiac sounds. Every deviation from the normal in beat and 
sound is the surest indication of an abnormity, be it in the struc¬ 
ture or be it in the mechanism of the heart. The difference in 
sound and beat, which in some affections appear more, in others 
less characterized, determine the nature of the existing affection 
with certainty or with greater or less probability. 
The normal heart-beat is felt behind the left ulna between the 
fifth and seventh ribs, in the depth, however, very indistinctly. 
The number of heart beats varies, according to the kind, size and 
age of the animal, and is certainly familiar to every practitioner. 
By placing the ear to the chest in the vicinity of the heart 
two sounds can be heard which are determined by the action of 
the heart and are designated cardiac sounds. By practice we can 
learn to distinguish perfectly the systolic and diastolic sounds in 
sound horses only. In sound animals both sounds are full, clear, 
rythmical, corresponding to the out and in-pouring of the blood 
in the cavity of the heart, without hindrance, in definite intervals. 
Cardiac sounds are, therefore, always regular and measured by 
intervals. Ttiey become familiar by practice. Thus auscultation 
is one of the most important diagnostical auxiliaries in diseases 
of the heart. 
Percussion is as important as auscultation. By percussion we 
are able to ascertain the size and position of the heart in the chest 
and its condition to the normal, and therefrom draw further con¬ 
clusions. 
The frequency and constitution of the pulse will give us infor¬ 
mation of the disorder of the mechanism of the heart, and tell us 
whether the condition be inflammatory, acute, or chronic. The 
natural condition of the respiration is less reliable, for often acute 
inflammatory diseases of the heart develop and terminate without 
the respiration having changed at the beginning of the disease. 
In chronic affections dyspnceis often constant. 
Therefore, as a rule, the following holds good : As soon as the 
respiration is striking and dyspnoe is obvious, no affection of the 
lungs or pleura being traceable, and no acute inflammatory disease 
present, then a suspicion of existing diseases of the heart is 
justified. 
