226
WILLIAM C. YOUNG
Although questioned from time to time for lower mammals as well as
for man (35), the hormonal basis of mating behavior is generally considered to be well established (9). Testicular androgen, presumably testosterone, is the effective hormone in the males of all species. Ovarian estrogen, presumably estradiol or a metabolite (134), is said to be effective
in the cat, dog, ferret, goat, pig, and rhesus monkey. Progesterone in
addition to estrogen is necessary for the normal display of estrus in the
guinea pig, rat, mouse, hamster, and sheep, and it seems to participate
along with estrogen in the induction of estrus in the cow and rabbit. The
mechanism of the action of progesterone is not known (330). The
suggestion found in the older as well as in the contemporary literature
that androgens and estrogens of adrenal cortical origin function in
maintaining the level of sexual behavior has not been demonstrated
by the results of investigations designed to test the point (9). This is
consistent with the conclusions that in adult males adrenal androgens
are much weaker than testicular androgens in the usual biological tests
and appear to be of little significance for the reproductive tract as substitutes for gonadal hormones, and that in females the stimulus of ovariectomy is not associated with any grossly detectable substitution by the
adrenals (331).
A number of aspects of the relationship between the hormones and
behavior in mammals have not yet been explained, although in no instance do substances different from those encountered in the other
vertebrate phyla seem to be involved. In male mammals there is commonly a slow decline in reproductive vigor following castration (9)
whereas in females, except in some ovariectomized rabbits
(332-334),
estrous behavior is not displayed after this operation. A number of male
fishes (57, 335, 336), an amphibian (160), and several birds (235, 237239) resemble mammals in this respect.
In most mammals in which estrogen and progesterone participate
in the preparation of the female for estrus, the relationship is synergistic
in the sense that normal behavior is not displayed unless progesterone
has been preceded by an action of estrogen. The sheep is different,
endogenous or exogenous estrogen must be preceded by progesterone
(337-344). No other example of its kind has come to the reviewer's attention at any phylogenetic level; it would seem that the existence of a
mechanism of action fundamentally different from that in the other
vertebrates must be postulated.
The relationship between the hormones and reproductive or erotic
behavior in primates is not clear and the subject has long been controversial (2, 6, 8, 9, 34^-36). As far as the male is concerned, the tendency
WILLIAM C. YOUNG
Although questioned from time to time for lower mammals as well as
for man (35), the hormonal basis of mating behavior is generally considered to be well established (9). Testicular androgen, presumably testosterone, is the effective hormone in the males of all species. Ovarian estrogen, presumably estradiol or a metabolite (134), is said to be effective
in the cat, dog, ferret, goat, pig, and rhesus monkey. Progesterone in
addition to estrogen is necessary for the normal display of estrus in the
guinea pig, rat, mouse, hamster, and sheep, and it seems to participate
along with estrogen in the induction of estrus in the cow and rabbit. The
mechanism of the action of progesterone is not known (330). The
suggestion found in the older as well as in the contemporary literature
that androgens and estrogens of adrenal cortical origin function in
maintaining the level of sexual behavior has not been demonstrated
by the results of investigations designed to test the point (9). This is
consistent with the conclusions that in adult males adrenal androgens
are much weaker than testicular androgens in the usual biological tests
and appear to be of little significance for the reproductive tract as substitutes for gonadal hormones, and that in females the stimulus of ovariectomy is not associated with any grossly detectable substitution by the
adrenals (331).
A number of aspects of the relationship between the hormones and
behavior in mammals have not yet been explained, although in no instance do substances different from those encountered in the other
vertebrate phyla seem to be involved. In male mammals there is commonly a slow decline in reproductive vigor following castration (9)
whereas in females, except in some ovariectomized rabbits
(332-334),
estrous behavior is not displayed after this operation. A number of male
fishes (57, 335, 336), an amphibian (160), and several birds (235, 237239) resemble mammals in this respect.
In most mammals in which estrogen and progesterone participate
in the preparation of the female for estrus, the relationship is synergistic
in the sense that normal behavior is not displayed unless progesterone
has been preceded by an action of estrogen. The sheep is different,
endogenous or exogenous estrogen must be preceded by progesterone
(337-344). No other example of its kind has come to the reviewer's attention at any phylogenetic level; it would seem that the existence of a
mechanism of action fundamentally different from that in the other
vertebrates must be postulated.
The relationship between the hormones and reproductive or erotic
behavior in primates is not clear and the subject has long been controversial (2, 6, 8, 9, 34^-36). As far as the male is concerned, the tendency