Year: 1869

why, no, my little girl"


90, I'm 80 glad then it isn't all a
dream r'-Ow Young Folks.


Work Performed by the Human Heart.


That wonderful little pumping engine
which we all carry around in our bosOms,
and which runs without cessation till death
ruthiessly closes the thro, tile, performs an
amount OF work SO great as to he almost
beyond belief till substantiated by arith-
metical calculation.


II we scrutnize the mechanism of the
heart, we shall find that it involves i'll its
operations nearly all the principles of
hydrOdynamics. 1t may, therefore, be
brought within the domain Of mathemat-
les as well as any other machine.


In the attempt to calculate the power
of the human heart for given time, we
shall arrive at some curious and interest
ing, not to say astonishing results. Few
would credit, at first, the statement that
the hearts now beating in and around the
city of New York, exert an aggregate power
ample to propel large steamer across
the Atlantic ocean at IA iair rate of speed,
vet we shall be able " demonstrate that
this is as much a fact, as that any of
these steamers ever crossed that storm
torn sea.


Blood is heavier than water its specific
gravity being, accordingto Booth, of from
l0527 to 1867. For convenience, how
ever, we shall consider it rs being of the
same weight as water, extreme accuracy
not being essential to our purpose, and III
our computations we shall, for the most
part and for the same reason, throw out
fractions and use round numbers.


The pressure required at the mouth of
the aorta to force the blood through the
vessels of the human body, is estimated
by IIalcs as being equal per square inch
of surface, to that exerted by u column of
blood seven and one-half feet high. The
pressure per square inch was estimated
by Poisenillc as four pounds three ounces
Others have estimated the pressure as
that of a column of water six feet lin hight
The results vary in different experiments,
but they ard sufficiently accurate to give
us an average that we may rely upon as
within bounds. They are also something
more than mere estimates, as this pressure
has been measured by pressuraSgages in
serted into the blood vessels.


We shall consider the pressure as that
of water column six feet in hight, the
weight of which would be nearly forty





consider forty-twO ounces, or two pounds
ten ounces avoirdupois.


The average discharge of the heart at
each pulsatiOn may be estimated at .one
and one half ounces, and its number of
beats at seventy five per minute: making
an aggregate of 112 ounces, or seven
pounds discharged pei minute.


The average internal diameter of the
aorta or the first great artery through
which the blood passes from the heart
into the general circulation, may be taken
as being in adults three-quarters of an
inch.


Seven pounds of blood per minute is
therefore forced through this artery
against a pressure of forty-twO ounces,
equivalent to raising seven pounds six
feet each minute, equal To raising forty
two pounds one foot, or forty-two foot
pounds.


From the diameter of the aorta and the
amount of blood forced through it we
might compute the velocity of flow, but
that is not essential to our purpose. All
consideration Of friction IN the perform
ance of this work is also omitted, 50 that
the estimate of forty two foot pounds per
minute must be considered as considerably
less than the actual work performed, this
result corresponding To what is called
u@fm aoork in the performance of ma
chimes.


Forty years of this work would be
equal To the work of twenty-six thousand
seven hundred and fifty seven horses for
| one minute of time, or the work of one
horse for forty-four and one half days Of
ten hours.


The work of seven hundred and eighty
six adult hearts is equal To one horse
power; therefore seven hundred and
eighty.six thousand hearts would perform
the work of one thousand horses. The
aggregate population of New York,
Brooklyn and Jersey City, was, accord
ing To the census of 1860, one million one
hundred and twenty thousand, and it may
be safely estimated now Mt one and one
| half millions. Considering this as equal
TO an adult population of twelve hundred
| thousand, their united heart beats exert a
power equal To that of one thousand five
hundred and twcnty-scven horses. Aver
aging the power of the united pulsations
of adults and children az equal To that oI
four -ffths the entire population, and taking
the census of 1860 as basis for cal
culation, the work done by all the human
hearts in the United States nearly equal!
that Of thirty-two thousand horses Tn,


work done by the beating of all the hu


man hearts on the globe is equivalent II


the power of one million forty six thou


sand and fifteen horses. The nomina


horse power of the engines i'm the Grea


Eastern is four thousand considering th'
actual horse power to be ten thousand, TIN
n l