Touch is not actually a single sense, but rather a combination of senses
including those that register cold, heat, touch, pressure, and pain.
Each component of the "sense of touch" uses unique nerve cells, having
different sensory structures at the receiving end.  For example, touch
nerves have an end that is elongated and bulb-shaped, nerves specialized
for heat look like twisted threads, and pain receptors lack a protective
sheath.  A single "touch" may any or all types of nerve receptors.  The
exact location and density of these nerves vary with species, as does
the proportion of different nerves within different parts of the parts of
the body.  The sense of touch is not just relegated to the external skin
surface, but nerve receptors are found throughout the body, including
those wrapped around the bones and within the teeth, in the major organs,
and the muscles, ligaments, and tendons.  Interestingly, the distribution
of pain receptors in the gastrointestinal mucosa is very similar to those
in the skin, making the entire gastrointestinal tract extremely sensitive
to painful stimuli and irritation.  The sense of touch is not just part
of tactile awareness, but may be also incorporated into other senses or
functions, such as balance.
 
The sense of touch is intimately and inexorably tied to the perception
of pain and discomfort.  Historically, there has been an attitude that
the conscious perception of pain and discomfort require higher brain
functions, so while animals may perceive pain (the sensory-discriminative
dimension) at the thalamus and lower brain centers, the interpretation of
that pain (the affective-motivational dimension) takes place in the
cerebral cortex.  In other words, the attitude suggests ferrets can feel
pain and react, but only humans could SUFFER from feeling pain.  This
attitude was extended into the realm of infant humans (possessing a
still-developing brain), where surgical procedures were done sans the
benefit of anesthesia or post-procedure pain medication (anesthesia was
done to control movement, NOT to relieve pain, a common motivation of
vets).  Excluding the dogmatic diatribes of philosophers, modern research
has shown such attitudes to be faulty, that both human infants AND
animals not only feel pain, but perceive it at a conscious level as well.
Coghill (1999) argues that "somatosensory components and affective
components of pain can be experimentally separated" (p. 73), but that
"current views that sensory-discriminative and affective-motivational
dimensions of pain are processed in parallel by distinct neural
structures cannot account for a number of aspects of pain." (p. 67).
Additionally, various types of brain scans have demonstrated multiple
parts of the brain interpret pain sensations, NOT JUST the cerebral
cortex.  Even more support is offered by Varner (1998), who presented
a table of six conditions "relevant to consciousness of pain in the
animal kingdom":
1. the presence of nociceptors [pain receptors];
2. the presence of a central nervous system [CNS];
3. whether the nociceptors are connected to the CNS;
4. whether endogenous opioids [pain killers produced by the body] are
   present;
5. whether analgesics affect responses; and
6. whether the behavioral responses are analogous to those of humans."
 
Ferrets met all six criteria, but then, so do nearly all mammals.  Put
simply, while the idea that pain perception and perception of suffering
takes place in different parts of the brain might be true, the idea that
complex brain structures are required for pain to leave the arena of
"stimuli" and enter the arena of "suffering" is not.  Consequently, human
babies are now medicated for pain, and the attitude is trickling into the
veterinary community as well.  Many vets are administering post-operative
pain medications, and are increasingly aware that animals not only feel
pain, but can also suffer from it.  MORE vets need to read the research
that shows faster healing rates, better outcomes, and less complications
from pets receiving post-operative pain medications.
 
Moving away from the philosophical debate on the perception of pain,
there is NO doubt that ferrets can FEEL pain.  Clip a nail quick or step
on a tail and you know the statement to be true.  Likewise, there is no
doubt ferrets have just as "normal" sense of touch as any other mammal,
humans included.  However, there ARE some regions of heightened sensory
awareness that can be exploited to enrich the ferret's sensory world.
Ferrets are very facially oriented in that they have a sensitive nose,
extremely sensitive whiskers, and tufts of tactilely sensitive hairs
around their eyes and ears.  Ferrets like to be touched, stroked, rubbed,
physically reassured, wrestled, scratched, warmed (or cooled), tickled,
and any number of other activities that stimulate the sense of touch.
Fortunately for us, all of these can become enrichment activities,
especially for ferrets living extended times in cages, or those old
or sick or incapable of other enrichments.  Besides the concept of
enrichment, there is an ever-increasing body of evidence suggesting the
positive responses to touch include improvements to the immune system,
mental faculties, and longevity.
 
Bob C
[Posted in FML issue 4218]