I'm glad friendship doesn't preclude your expression of disagreement! ;-)
Amicable debate is GOOD!  While I would never say some sort of nasal blow
wouldn't cause damage, I stand by my statement that the construction of the
ferret's nose eliminates most possibilities of injury due to nose thumping.
I am glad, however, that you did not read into my statements and conclude
I thought corporal punishment was acceptable.  I do not, simply because
1) I have a philosophy of non-violence, and 2), negative reinforcement
ultimately fails while positive reinforcement usually works (in those
instances where the training does not fight instinct).  Thus, I do not
support nose flicking or thumping.  Besides, I think it hurts the ferret
more than we realize.
 
Those thin delicate bones you are talking about are nasal turbinates (or
chonchae).  These bones are quite irregular, possess a complex fractal
shape and are paper thin.  The bones are attached to the interior side
walls of the skull and fill a large part of the nasal cavity.  The nose
itself is basically a thick pad of nerve-rich skin, mounted on a cartilage
base.  This cartilage base extends forward of the skull about 7 to 10 mm
(you can feel where it attaches with your finger) and has a long midline
"root" of septal cartilage, which extends into the nasal aperture and
separates the nasal cavity into right and left sides.  The outer rim of
the nose cartilage is attached to the outer rim of the nasal aperture
(feel your own nose and you get the idea).  Now, if you followed this
basic description, you will notice that at no place does the exterior nose
actually come into contact with those thin turbinates.  Thus, while they
reside inside the nasal aperture and are fused to portions of the ethmoid,
maxillary and nasal bones, they are not actually part of the external nose
structure.
 
Whacking the front of the nose compresses the nasal leather into the nasal
cartilage, compressing it into bone.  Cartilage is one hell of a great
shock absorber, which is why it is used to protect joint surfaces and is
a major component of intervertebral disks.  Any force applied to the nose
must be in excess of that which would be naturally absorbed by the
cartilage JUST to be transmitted to the bone.  In more biomechanical terms,
light and even moderate nose thumping, however painful to the sensory-rich
nose leather, does not provide enough energy to damage the turbinates
because it is absorbed by the cartilage and transmitted to the bones of the
skull; there is NO direct mode of transmission to the turbinates.  To be
direct, it would take one hell of a powerful finger to be able to transmit
enough energy to cause direct harm to the bones or cartilage of the
ferret's nasal structures.  Long before interior damage would occur, there
would be obvious exterior damage, which would probably include crushing
injuries to the nose leather, to the cartilaginous skeleton of the external
nose, and perhaps even to the rim of bone which forms the exterior portion
of the nasal aperture.
 
As for third party reports of damage caused by nasal thumping, I cannot
evaluate them and determine the actual damage (I am NOT implying dishonesty
in reporting; I am just unable to confirm the damage, which is a
requirement for scientific evaluation.  Perhaps you can email me the exact
damage report).  It IS possible that if significant force was applied, say
by kicking the ferret in the nose, that enough force could be transmitted
along the nasal septum which could damage the ethmoid, but (as I indicated
before) such force would also be sufficient to fracture skull bones (it
would probably break the upper jaw, and there is no telling of the damage
it could do to the neck).  If the nasal septum was quickly compressed
with enough force, it could buckle or fracture, which might damage the
turbinates.  However, this force is clearly excessive compared to finger
thumping.  The turbinates are frequently poorly ossified in healthy
animals, and in many cases are plain old cartilage.  While the primary
reason is to reduce the bone-to-nasal-mucosa ratio (allowing more space
for olfaction as well as less weight), at least part of the reason is to
give a degree of flexibility so swollen tissue won't break the turbinate
bones.  Thus, it is unlikely minor or even moderate osteoporosis would
matter.  In terms of age, kits DO have bones which are not as well ossified
as those in adults, but don't forget kits are weaned to meat and bone PRIOR
to their eyes opening; this implies the degree of bone ossification in the
skull would be sufficient to chew, so it would protect the turbinates as
well.
 
I understand people want a physical reason to refute nose thumping, so
a few are upset I would discount the bone injury idea.  Sorry, but I am
compelled to answer questions as truthfully as possible or understood.
While my answer might not provide direct rebuttal to thumping, there are
at least two areas which COULD be explored to provide such support;
1) negative training reinforcement v.  positive reinforcement, and
2) thumping the nerve-rich nose pad probably hurts the ferret far more than
people realize.  Ferrets are pretty stoic creatures and just because they
don't whimper when whacked, doesn't mean it doesn't hurt like hell.  I've
seen ferrets tear across a room and bump their heads and just dance around,
but when they bump their nose, they'll stop, shake their heads and blink
tears.  That nose is VERY sensitive and the pain produced by thumping might
be out of proportion to the desired result.  Think about it.
 
Bob C and 16 Mo' Nosey Carnivore Critters
[Posted in FML issue 3064]