4. HORMONES AND BEHAVIOR
227
to discount the role of testicular hormones has its basis in part on the
persistence of erotic behavior following castration. This, however, is not
peculiar to man or even to primates. As we have just seen, sexual behavior declines slowly following the castration of male fishes, amphibians, and birds that have been studied. Beach (345) notes briefly that
there are some dogs in which there is no detectable loss of sexual
responsiveness or ability to copulate up to two years after castration. In
female primates the change is well documented (9). Within the chimpanzee, receptivity coincides with most of the long follicular phase of
the cycle, and in the human female it is coextensive with the entire cycle.
Tentatively Beach (345, 346) attributes this change to the greater degree
of cortical control over sexuality in these species and the greater extent
to which the sexual arousal mechanism is affected by symbolic factors.
In this place it is important to note that the change is postulated to have
occurred within the nervous rather than within the endocrine system.
Discussion of the identification and cellular origin of gonadal hormones in mammals has been facilitated by the appearance of several
comprehensive reviews within the last year (143-146, 347). The use of
modern methods has revealed what was long suspected from bioassays
and tissue responses, namely that the hormones are identical chemically
with the gonadal hormones of the lower vertebrates. Testosterone is
the most active hormone secreted by the testis, and estradiol-17/? and
estrone, encountered as the predominant hormones in female fishes, amphibians, reptiles, and birds, are the most active hormones secreted by
the mammalian ovary. Testosterone is generally believed to be synthesized by interstitial or Ley dig cells. No satisfactory evidence has been
obtained in support of the view advanced in the early 1940's that testicular estrogens are produced by Sertoli cells. With respect to the ovary
uncertainty exists. The specific suggestions have been made that estrogens are secreted by cells of the theca interna and interstitial cells, that
androgens are secreted by interstitial cells and by hilus cells located
along the unmyelinated nerve and blood vessels of the ovarian medulla
and mesovarium (348), and that progesterone is secreted by granulosa
lutein cells. More recently evidence has been presented that 20ahydroxypregn-4-en-3-one rather than progesterone is the principal gestagen produced by the ovary of the New Zealand white rabbit and that
it is synthesized by the interstitial cells which in this and other breeds
of rabbits resemble luteal tissue (348a). A view encompassing all these
suggestions is expressed by Eckstein (143), who stated that hormone
production may be an inherent property of the four major elements—
the granulosa, theca interna, corpus luteum, and interstitial cells. Either
227
to discount the role of testicular hormones has its basis in part on the
persistence of erotic behavior following castration. This, however, is not
peculiar to man or even to primates. As we have just seen, sexual behavior declines slowly following the castration of male fishes, amphibians, and birds that have been studied. Beach (345) notes briefly that
there are some dogs in which there is no detectable loss of sexual
responsiveness or ability to copulate up to two years after castration. In
female primates the change is well documented (9). Within the chimpanzee, receptivity coincides with most of the long follicular phase of
the cycle, and in the human female it is coextensive with the entire cycle.
Tentatively Beach (345, 346) attributes this change to the greater degree
of cortical control over sexuality in these species and the greater extent
to which the sexual arousal mechanism is affected by symbolic factors.
In this place it is important to note that the change is postulated to have
occurred within the nervous rather than within the endocrine system.
Discussion of the identification and cellular origin of gonadal hormones in mammals has been facilitated by the appearance of several
comprehensive reviews within the last year (143-146, 347). The use of
modern methods has revealed what was long suspected from bioassays
and tissue responses, namely that the hormones are identical chemically
with the gonadal hormones of the lower vertebrates. Testosterone is
the most active hormone secreted by the testis, and estradiol-17/? and
estrone, encountered as the predominant hormones in female fishes, amphibians, reptiles, and birds, are the most active hormones secreted by
the mammalian ovary. Testosterone is generally believed to be synthesized by interstitial or Ley dig cells. No satisfactory evidence has been
obtained in support of the view advanced in the early 1940's that testicular estrogens are produced by Sertoli cells. With respect to the ovary
uncertainty exists. The specific suggestions have been made that estrogens are secreted by cells of the theca interna and interstitial cells, that
androgens are secreted by interstitial cells and by hilus cells located
along the unmyelinated nerve and blood vessels of the ovarian medulla
and mesovarium (348), and that progesterone is secreted by granulosa
lutein cells. More recently evidence has been presented that 20ahydroxypregn-4-en-3-one rather than progesterone is the principal gestagen produced by the ovary of the New Zealand white rabbit and that
it is synthesized by the interstitial cells which in this and other breeds
of rabbits resemble luteal tissue (348a). A view encompassing all these
suggestions is expressed by Eckstein (143), who stated that hormone
production may be an inherent property of the four major elements—
the granulosa, theca interna, corpus luteum, and interstitial cells. Either