198 ON DISEASES OF THE HEART OF THE HORSE. 
tricle causes the coats of these vessels to yield and dilate beyond 
their power to contract; the blood stagnates in them; rupture 
of their tunics may take place; congestion may form; or the 
seriferous arteries commence an increased action, and oedema of 
the lungs be the result; and which, rapidly extending, speedily 
suffocates the animal, as clearly displayed in the case of the mare, 
related at page 26 of the January No. for 1833. 
Having briefly described the probable commencement, pro¬ 
gress, and termination of hypertrophy and dilatation—a theory 
deduced from indications during life and examinations after 
death—the symptoms prognosticating these affections will be 
more readily conceived. We are liable to confound hypertrophy, 
and its sequelae, of the right side of the heart with pneumonia, 
from the disturbance in the respiration, as it is in the lungs 
that the secondary lesions occur: I will therefore proceed to de¬ 
scribe the symptoms in the last stage of this malady, necessarily 
fatal, as I previously observed that this is the stage when we arc 
commonly required to make our examination. 
I know of no outward signs by which its presence may be de¬ 
tected at an early period, and before fatal lesion in the lungs is 
fully developed ; auscultation, ascertaining the contractions and 
rythm of the heart, can alone make known its existence. The 
distinction from the character of these in health can only be re¬ 
cognized by a studious observation of the action of the organ, a 
practice highly to be recommended. W'e need no stethoscope, 
for the ear can be readily applied for this purpose. 
By auscultation we are enabled to judge of the alternate con- 
traciiori of the ventricle and auricle; their extent, duration, 
force, regularity, and simultaneousness; and that both on the 
right and on the left side. 
In listening to the heart’s ri/thn (by which is meant the order 
of contraction of the several cavities, their respective dura¬ 
tion, succession, and relation to each other in a healthy horse, 
whose heart is in a state favourable to the performance of all its 
functions), we first hear that of the ventricle, a somewhat long 
dull sound ; and immediately following, and without interval, a 
louder and shorter sound, which is that of the auricle. Then 
comes a perfect repose. Of the whole period occupied by a com¬ 
plete contraction and repose of the heart, about one-third is 
taken up by the ventricles, a fourth by the auricles, the rest by 
the absolute repose : and when the organ is healthy and properly 
proportioned, these relations exist, whether the contractions are 
quick or slow. When we come to study the changes from these 
movements of the healthy organ, movements which must be 
heard to be known, no language being ceipablc of conveying a 
just idea of their character, and compare the phenomena with 
