of the phenomena of certain lesions in the abdominal cavity.
The nociceptors in the abdomen, like nociceptors elsewhere, have been
established as a result of some kind of injury to which during
vast periods of time this region has been frequently exposed.
On this premise, we should at once conclude that there are no
nociceptors for heat within the abdomen because, during countless years,
the intra-abdominal region never came into contact with heat.
That this inference is correct is shown by the fact that the
application of a thermocautery to the intestines when completing
a colostomy in a conscious patient is absolutely painless.
One would conclude also that there are no touch receptors in the
abdominal viscera, and therefore no sense of touch in the peritoneum.
Just as the larynx, the ear, the nose, the sole of the foot,
and the skin have all developed the specific type of nociceptors
which are adapted for their specific protective purposes, and which,
when adequately stimulated, respond in a specific manner in accordance
with the law of phylogenetic association, so, the abdominal viscera
have developed equally specific nociceptors as a protection against
specific nocuous influences. The principal harmful influences
to which the abdominal viscera have been exposed during vast periods
of time are deep tearing injuries by teeth and claws in the innumerable
struggles of our progenitors with each other and with their enemies
(Fig. 9); peritonitis caused by perforations of the intestinal
tract from ulcers, injuries, appendicitis, gall-stones, etc.;
and overdistention of the hollow viscera by various forms of obstruction.
Whatever may be the explanation, it is a fact that the type
of trauma which results from fighting corresponds closely with
that which causes the most shock in the experimental laboratory.
Division of the intestines with a sharp knife causes no pain,
but pulling on the mesentery elicits pain. Ligating the stump