Edited by Dava Sobel
The heart will have no interruption,
begins as a simple tube (blood flow undivided)
at the middle of embryo
hurried—task of branching sufficient blood
levels into all upcoming situations. (in-roads throughout the growing body)
The heart, quick, outgrows its own
allotted cavity, and bends a branch right (every time)
and back—pivots into
the cardiac loop, plotting
pistons, to hang self-knotting,
strung-up. The blood muscle must
raise divisions. The hollow heart
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now split, turns intrinsic—walling out
a partition, a pocket, a sinus to house
the pulmonary hinges—a body’s
bloodlines soon become confluent (before bringing back a breath)
to enter the heart.
When later more transitional twisting
has caused a furrow, external,
the interfacing ventricle wall will
thicken—meshwork of muscular
fetters tuck together, reach out,
near-bridge for the atrial pacemaker.
An intra-arterial hollow so self-established. (lock and chamber)
Meanwhile, against the narrower walls
and paired opposite, loose masses
of migratory tissue (from the mesoderm)
driven. Could linger on,
the non-particular life of a stem cell.
But here soft commotion reaching out,
endocardial cushions obstruct
the blood rush into opposite corners.
Predestined axes of embryo, peristalsis
in a pre-valved hollow—the body’s
first organ to engine
an animal’s ontogeny,
the heart
as it begins to beat.