To heal by tertiary intention is to leave the wound open
on purpose; you see it most often in the gritty sort of
traumas that leave large chunks of dirt and debris behind,
embedded in the still-injured tissue.  People often
wonder why this is done, as it is natural within our impulsive
nature to cover up something so grotesque and unsightly
by hastily wrapping it together with hopeful wishes that
goodwill can do the healing on its own.  But the reality
is that the body sometimes has a slow memory, allowing
itself to become inflamed and irritable long after the
incident has passed.  Those are the sort of wounds for
which doing something may be worse than doing
nothing.

To heal by secondary intention moves to the next stage,
when we are prepared to begin cleaning out the leftover
mess after the body is done venting itself.  It is usually a
daily exercise, in which new and clean bandages must
be applied in order to gently and gradually draw out the
last vestiges of reactive poison.  The more severe
the wound, the more futile the efforts might seem at
first, but the deliberate lack of provocation and the soft
presence of something to absorb the weeping, mixed
residue is surprisingly, though subtly, effective.

To heal by primary intention is to bring out that piercing
needle and stitch those last, ragged edges of a wound
together, laying them side by side so that the two bits of
flesh that were once so violently torn apart now have
no choice but to cleave together again.  It is painful,
often messy, and decidedly uncomfortable as the nature
of the wound is to pull against the unyielding sutures that
unceremoniously bind it up.  But it is also the form of
healing that leaves the smallest of scars and restores
as much strength as is possible after so traumatic a rift.
It is the preferred method, and one that stands the test of
time.