Studies in the Psychology of Sex, Volume 4 | Page 9

that voluntary
exertion diminishes the energy of sensation.[11] This explanation is,
however, inadmissible, for, although we cannot easily tickle ourselves
by the contact of the skin with our own fingers, we can do so with the
aid of a foreign body, like a feather. We may perhaps suppose that, as
ticklishness has probably developed under the influence of natural
selection as a method of protection against attack and a warning of the
approach of foreign bodies, its end would be defeated if it involved a
simple reaction to the contact of the organism with itself. This need of
protection it is which involves the necessity of a minimal excitation
producing a maximal effect, though the mechanism whereby this takes
place has caused considerable discussion. We may, it is probable, best
account for it by invoking the summation-irradiation theory of
pain-pleasure, the summation of the stimuli in their course through the
nerves, aided by capillary congestion, leading to irradiation due to
anastomoses between the tactile corpuscles, not to speak of the much
wider irradiation which is possible by means of central nervous
connections.
Prof. C.L. Herrick adopts this explanation of the phenomena of tickling,
and rests it, in part, on Dogiel's study of the tactile corpuscles
("Psychological Corollaries of Modern Neurological Discoveries,"
Journal of Comparative Neurology, March, 1898). The following
remarks of Prof. A. Allin may also be quoted in further explanation of
the same theory: "So far as ticklishness is concerned, a very important
factor in the production of this feeling is undoubtedly that of the
summation of stimuli. In a research of Stirling's, carried on under
Ludwig's direction, it was shown that reflex contractions only occur
from repeated shocks to the nerve-centres--that is, through summation

of successive stimuli. That this result is also due in some degree to an
alternating increase in the sensibility of the various areas in question
from altered supply of blood is reasonably certain. As a consequence of
this summation-process there would result in many cases and in cases
of excessive nervous discharge the opposite of pleasure, namely: pain.
A number of instances have been recorded of death resulting from
tickling, and there is no reason to doubt the truth of the statement that
Simon de Montfort, during the persecution of the Albigenses, put some
of them to death by tickling the soles of their feet with a feather. An
additional causal factor in the production of tickling may lie in the
nature and structure of the nervous process involved in perception in
general. According to certain histological researches of recent years we
know that between the sense-organs and the central nervous system
there exist closely connected chains of conductors or neurons, along
which an impression received by a single sensory cell on the periphery
is propagated avalanchelike through an increasing number of neurons
until the brain is reached. If on the periphery a single cell is excited the
avalanchelike process continues until finally hundreds or thousands of
nerve-cells in the cortex are aroused to considerable activity. Golgi,
Ramón y Cajal, Koelliker, Held, Retzius, and others have demonstrated
the histological basis of this law for vision, hearing, and smell, and we
may safely assume from the phenomena of tickling that the sense of
touch is not lacking in a similar arrangement. May not a suggestion be
offered, with some plausibility, that even in ideal or representative
tickling, where tickling results, say, from someone pointing a finger at
the ticklish places, this avalanchelike process may be incited from
central centres, thus producing, although in a modified degree, the
pleasant phenomena in question? As to the deepest causal factor, I
should say that tickling is the result of vasomotor shock." (A. Allin,
"On Laughter," Psychological Review, May, 1903.)
The intellectual element in tickling conies out in its connection with
laughter and the sense of the comic, of which it may be said to
constitute the physical basis. While we are not here concerned with
laughter and the comic sense,--a subject which has lately attracted
considerable attention,--it may be instructive to point out that there is
more than an analogy between laughter and the phenomena of sexual

tumescence and detumescence. The process whereby prolonged
tickling, with its nervous summation and irradiation and accompanying
hyperæmia, finds sudden relief in an explosion of laughter is a real
example of tumescence--as it has been defined in the study in another
volume entitled "An Analysis of the Sexual Impulse"--resulting finally
in the orgasm of detumescence. The reality of the connection between
the sexual embrace and tickling is indicated by the fact that in some
languages, as in that of the Fuegians,[12] the same word is applied to
both. That ordinary tickling is not sexual is due to the circumstances of
the case and the regions to which the tickling is applied. If, however,
the