APPENDIX B.

Histories of Sexual Development.




SEXUAL SELECTION IN MAN.

The External Sensory Stimuli Affecting Selection in Man--The Four Senses
Involved.


Tumescence--the process by which the organism is brought into the physical
and psychic state necessary to insure conjugation and detumescence--to
some extent comes about through the spontaneous action of internal forces.
To that extent it is analogous to the physical and psychic changes which
accompany the gradual filling of the bladder and precede its evacuation.
But even among animals who are by no means high in the zoölogical scale
the process is more complicated than this. External stimuli act at every
stage, arousing or heightening the process of tumescence, and in normal
human beings it may be said that the process is never completed without
the aid of such stimuli, for even in the auto-erotic sphere external
stimuli are still active, either actually or in imagination.

The chief stimuli which influence tumescence and thus direct sexual choice
come chiefly--indeed, exclusively--through the four senses of touch,
smell, hearing, and sight. All the phenomena of sexual selection, so far
as they are based externally, act through these four senses.[1] The