SECT. IX. PHYSIOLOGY. 81 
SECTION IX. - 
Cardial Irritability. 
** By the contraction of the ventricles, it propels the blood 
through the arteries, and by the dilatation of the auricles, it 
pumps it from the veins.”——Carson. 
. 
cLxxxv. The heart is composed of strong 
muscular fibres, which decussate each other in all 
directions, and are so interlaced together, as to 
defy description. They are arranged in such a 
manner as to form four distinct cavities, which 
necessarily vary in dimension according to the 
state of the fibres by which they are formed. 
The fibres of the heart are eminently endowed 
with irritability, which is called their systole and 
diostole; these terms, however, signify nothing 
more than expansion and contraction. 
cLxxxvi. The heart is supplied with nerves 
from the eighth pair and the great sympathetic. 
cLxxxvu. It has been much agitated, whether 
expansion or contraction of the heart be the active 
state of this muscle: Haller and Bichat contend 
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