Microscopical Science_, vol. xliv, Part I, 1900. Estrus has since
been fully discussed in Marshall's _Physiology of Reproduction_.)
This description clearly brings out the fundamentally vascular
character of the process I have termed "tumescence"; it must be
added, however, that in man the nervous elements in the process
tend to become more conspicuous, and more or less obliterate
these primitive limitations of sexual desire. (See "Sexual
Periodicity" in the first volume of these _Studies_.)

Moll subsequently restated his position with reference to my
somewhat different analysis of the sexual impulse, still
maintaining his original view ("Analyse des Geschlechtstriebes,"
_Medizinische Klinik_, Nos. 12 and 13, 1905; also _Geschlecht und
Gesellschaft_, vol. ii, Nos. 9 and 10). Numa Praetorius
(_Jahrbuch für Sexeuelle Zwischenstufen_, 1904, p. 592) accepts
contrectation, tumescence, and detumescence as all being stages
in the same process, contrectation, which he defines as the
sexual craving for a definite individual, coming first. Robert
Müller (_Sexualbiologie_, 1907, p. 37) criticises Moll much in
the same sense as I have done and considers that contrectation
and detumescence cannot be separated, but are two expressions of
the same impulse; so also Max Katte, "Die Präliminarien des
Geschlechtsaktes," _Zeitschrift für Sexualwissenschaft_, Oct.,
1908, and G. Saint-Paul, _L'Homosexualité et les Types
Homosexuels_, 1910, p. 390.

While I regard Moll's analysis as a valuable contribution to the
elucidation of the sexual impulse, I must repeat that I cannot
regard it as final or completely adequate. As I understand the
process, contrectation is an incident in the development of