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 tickling is applied within
the sexual sphere, then there is a tendency for orgasm to take place
instead of laughter. The connection which, through the phenomena of
tickling, laughter thus bears to the sexual sphere is well indicated, as
Groos has pointed out, by the fact that in sexually-minded people sexual
allusions tend to produce laughter, this being the method by which they