The Louisiana Democrat. [volume] (Alexandria, La.) 1845-1918, 1870-01-26
Work Performed by the Human
Heart.

n
closes the throttle. performs an
amount of work so great as to be almost
beyond belief till substantiated by aritbme.
teal calculation.
If we scrutlnize the mechanism of tho
heart, we shall find that it involves in ;ts
operations nearly all the principles Of nv.
drodnamics. 1t may, therefore, be brought
within the domain OF mathematics as Well
as any other machine.
In the attempt to calculate the power
of the human heart for a given time, va
shall arrive at some curious and interest.
ing, not for 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 now.
er ample to propel large steamer across
the Atlantic ocean at fair rate OF speed
yet we shall be able to demonstrate that
this is as much fact, as that any Of
these steamers ever crossed that storm.
torn sea.
Blood is heavier than water its spe.
cific gravity being. according to Booth, OF
from ,,0j27 to 1867. For CONVENIENCE
however, we shall consider it as being Of
the same weight as water, extreme accurs-
cy not being essential to our purpose, and
in 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 aorto to force the blood through the
vessels Of the human body, is estimated BY
Hales as being equal per square inch Of
surface, to that eXerted by column Of
blood seven and one-half feet high. Ths
pressure per square inch was estimated hy
by PoiseniIle asNour pounds three ounces.
Others have estimated the pressure as that
of column of water six feet 10 height.
The results vary in different experiments;
but they are sufficiently accurate to give US.
an average that We may rely upon as with
in bounds. They are also something more
than mere estimates. as this pressure has
been measured by pressure cages inserted
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 fOrytwo
ounces. which. for simplicity, We will con-
slider forty-two ounces, or two pouEsS 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 s-venty-fye per minute: making
an aggregate of III ounces, or sevea
pounds discharged per 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
Il pressure of furiy-two ounces, equivalent
to raising seven pounds six feet each
minute. equal to raising forty-two pounds
one foot, or fortytw footponnds.
!. From the diameter of the aarta and the
amount Of blood forced through it We
might compute the velocity Of flow, but
that in not essential to our purpose, All
consideration of friction in the performances
Of this work is also oinitten, So that the
estimate of forty-two foot-pounds per
minute must be considered as considera-
bly, less than the ac' nal work performed.
this result corresponding to what is called
useful work in the performance Of ma.
chimes.
Forty years of this work wou.d be equal
to the work Of twenty-six thousand seven
hundred aud fltyseven horses for and
minute of time, or the work of one horse
for forty four and one half days of ten
tours.
The work Of seven hundred and eighty
six adult hearts is equal 10 one-borse pow
er therefore seven hundred and eighty
| -, ~ ,Nt...ai,l h.x
work of one Thousand horses. The agerp,
gate population OF New York. Brooklyn
and Jersey. City. Was according to thu
censue Of 1860, one million one hundred
and twenty-thousand aud it may be safely
estimated now at one and one half millions.
Considering this as equal to an adult
population of twelve hundred thousand
their united heart beats exert power
equal to that of one thousand five hundred
and twenty-seven horses. Averaging tbs
power Of the united pulsations OF adults
and children as equal to that OF four tifsls
the entire population, and taking the cen
sus of 1860 as basis for calculation, tht
work done by all the human hearts in th,
United States nearly equals that of thirty
two thousand horses. The work done b,
the beating of all the human hearts on tn,
globe is equivalent to the power of on
million forty six thousand and fiiteel
horses The nominal horse power Of ID,
engines in the Great Eastern is four th0us
and considering the actual horse powe
to be ten thousand, the power exerted b!
the humad heartbeat of the world is sufli
cient to propel feet OF one hundred ant
four Great Easterns at full speed c0niip
ually. This power could only be generates
in average steam engineering practice b,
the combination Of four thousand six hnnd
red and eighty tons of coal per hour.
| When we reflect that the human fanil
is small in comparison even with the grea
class of mammaia, of which it forms PAL
and that many of the same class as th
whale, the elephant, the rhinoceroi
hippopotamus. giraffe, etc, have hearts Q
, very much greater SIZE and power than tb
human heart; and when we conceive Q
the enormous additional work performe'
by the hearts of reptiles, birds, fishes
mulluSks. and insects, and to this woil
} add IN imagination the power expended j
, the movement of the respiratory npparatu
of ANIMALS, and voluntary Muscular move
ment necessary TO obtain sustenence 10
t these animals. we may gain some feebl
conception Of the enormous eXpenditnr
of mechanical power required to sustai
animated existence on the earth. l. -ScieI
tiEo