PHYSIOLOGY. 
The motions of any part of the heart, eon- 
sidered singly and individnally, consist in a 
constant series of alternate contractions 
and dilatations ; or as they are technically 
named, alternate states of systole and dia- 
stole. The contractions take place as in 
other muscles, the dilating cause consists in 
the forcible entrance of blood into the ca- 
vity. The auricles and ventricles, when 
viewed in relation to each other, are suc- 
cessively contracted and dilated ; the cor- 
responding parts acting at the same time on 
both sides of the heart. Thus, when the au- 
ricles contract, in order to expel the blood, 
which they have received from the system 
at large, and from the lungs, the ventricles 
are relaxed, ’and therefore in a state fit for 
receiving this blood. When, in the follow- 
ing moment, the recently filled ventricles 
contract, in order to urge forwards the 
blood into the two arterial trunks, the auri- 
cles are relaxed, and become immediately 
distended by the current of venous blood. 
The action of the heart, and of the ves- 
sels connected with it, may therefore be 
distributed into successive periods. In the 
first of these, the venae cavae and pulmo- 
nary veins pour their blood into the two 
auricles, and thus cause a diastole of these 
cavities. The systole of the auricles trans- 
mits the blood into the ventricles in the 
second period ; and these latter cavities ex- 
pel their contents into the arteries in the 
third portion of time. Thus the action of 
the veins takes place at the same point of 
time with that of the ventricles ; and the 
contraction of the auricles is synchronous 
with that of the arteries. 
The systole of the ventricles, which is 
supposed to occupy one third of the time 
of the whole pulsation of the heart, is ac- 
complished by an approximation of the sides 
of the cavities to the middle partition, and 
of the apex to the basis of the heart. The 
whole viscus by this means becomes shorter 
and more obtuse. The well known fact of 
the heart striking against the left breast 
in its contraction, may seem on tlie first 
glance to refute this account of the systole 
of the ventricles. But, on a further exami- 
nation, it can have no such effect ; since the 
phenomenon in question depends on two 
causes amply sufficient to produce the effect. 
The swelling of the auricles, which are at 
the back of the heart, and particularly of 
the left auricle, which is interposed between 
the spine and the base of the left venticle, 
necessarily causes the point of the heart to 
advance towards the side; and this motion 
may be imitated in the dead body by in' 
jecting.or inflating the muscles. The other 
cause consists in the connection of the large 
arteries, particularly of the aorta, witli the 
base of the heart. A curved and flexible 
tube, when suddenly distended, become* 
in some measure straightened. Thus, when 
the blood is impelled into the aorta, the 
curve of ‘hat vessel approaches more nearly 
to a straight line. Its posterior end being 
firmly attached to the vertebr*, is immove- 
able ; to its anterior and moveable part is 
fixed the heart, which, by the straightening 
of the vessel, is obliged to describe a por- 
tion of a circle, in doing which, the apex 
strikes against the side. These two circum- 
stances occur simultaneously; the venous 
blood rushes into the auricles at the same 
time that the ventricle fills the aorta. The 
impulse of the blood expelled by the aortic 
ventricle is felt in the whole arterial sys- 
tem ; and it produces in alt arteries, which 
come within the sphere^of the touch, and 
which have an area of not less than one- 
sixth of a line in diameter, an obvious and 
perceptible effect, called the pulse, which is 
a real state cf diastole of the artery, and 
which is ascertained to correspond exactly, 
and to be perfectly synchronous with the 
systole of the heart. The number of pulsa- 
tions in a given space of time varies infi- 
nitely in healthy persons. Age is the chief 
cause of these varieties ; but other circum- 
stances, which constitute the peculiar state 
of health of each individual, have consider- 
able effect; so that no standard can be 
settled which shall prove generally correct. 
The following numbers afford, we believe, 
as near an approximation as can be expect- 
ed amidst so much uncertainty; they will 
serve at least as a comparative view in sub- 
jects of different ages. The heart of an in- 
fant, sleeping tranquilly, performs in the 
first days of existence about 140 pulsations 
in a minute ; at the end of the first year the- 
pulsations are, in the same space of time, 124, 
At the end of the second year 110 
Third and following years 96 
Seventh and following 86 
Time of puberty 80 
Manhood 75 
Sixtieth year 65 
The pulsations of the heart proceed in 
regular and continued succession to the last 
period of life, and then all its parts do not 
cease to act at once; but the right auricle 
and ventricle survive the opposite cavities 
for some little time, so that the former part 
