216
WILLIAM C. YOUNG
pora lutea which resemble those in mammals except for the absence of
blood vessels in the central portion (135, 197, 198). The androgenic
action of alcoholic extracts of testes from the snakes Bothrops and
Crotalus, and the estrogenic action of alcoholic extracts of ovaries from
these species were demonstrated by Valle and Valle (199). Extracts of
corpora lutea from the same females gave a 2-f- endometrial reaction in
the McPhail assay for progesterone (200). Vaginal estrus in mice was
induced by 4 daily injections of 0.1 ml. follicular fluid from Crotalus
(201). A substance with progesterone-like activity was extracted from
the plasma of two pregnant water snakes, Natrix s. sipedon (202). The
concentration rose from 0.3-1.0 ,/xg. equivalent of progesterone per milliliter of plasma in individuals with inactive ovaries or preovulatory follicles to 2 μg. following ovulation, to 4 μg. by mid-pregnancy, and to
8
at full term.
VII. Birds
Interest in the relationship of the hormones to behavior in birds has
a long history and is second only to that in mammals. For the most part,
activity has been directed toward an elucidation of the role of the
hypothalamicopituitary system and the gonadal hormones in the expression and control of reproductive behavior and migration. Professional
and amateur ornithologists, endocrinologists, morphologists, psychologists, ethologists, and poultry husbandrymen have participated. A recounting of the enormous literature would be out of place here, but a
number of recent reviews of descriptive and experimental studies contain
references to species that have been studied, much about their behavior,
and details of methodology by which quantification has become possible
(5,
7,203-208).
Many birds migrate, and in all except the parasitic species
(209-213)
the behavioral sequence which is a part of the reproductive process is
commonly composed of territorial establishment and defense, nest building, courtship, mating, egg laying, incubation, and parental care. The
sequence probably is more elaborate than any encountered in the other
vertebrate phyla. Many factors such as seasonal and meteorological
changes, food, nesting sites, nesting materials, and especially interpersonal relationships influence this behavior (7), but agreement is general
that once the process starts at the beginning of the reproductive season,
a certain endocrine readiness must exist before the next step will be
taken.
The relationship of the hormones to migration is equivocal (208,
214-218).
Experimental analysis of the problem is difBcult, and conceptualization must be broad enough to cover the two sexes. Any theory
WILLIAM C. YOUNG
pora lutea which resemble those in mammals except for the absence of
blood vessels in the central portion (135, 197, 198). The androgenic
action of alcoholic extracts of testes from the snakes Bothrops and
Crotalus, and the estrogenic action of alcoholic extracts of ovaries from
these species were demonstrated by Valle and Valle (199). Extracts of
corpora lutea from the same females gave a 2-f- endometrial reaction in
the McPhail assay for progesterone (200). Vaginal estrus in mice was
induced by 4 daily injections of 0.1 ml. follicular fluid from Crotalus
(201). A substance with progesterone-like activity was extracted from
the plasma of two pregnant water snakes, Natrix s. sipedon (202). The
concentration rose from 0.3-1.0 ,/xg. equivalent of progesterone per milliliter of plasma in individuals with inactive ovaries or preovulatory follicles to 2 μg. following ovulation, to 4 μg. by mid-pregnancy, and to
8
at full term.
VII. Birds
Interest in the relationship of the hormones to behavior in birds has
a long history and is second only to that in mammals. For the most part,
activity has been directed toward an elucidation of the role of the
hypothalamicopituitary system and the gonadal hormones in the expression and control of reproductive behavior and migration. Professional
and amateur ornithologists, endocrinologists, morphologists, psychologists, ethologists, and poultry husbandrymen have participated. A recounting of the enormous literature would be out of place here, but a
number of recent reviews of descriptive and experimental studies contain
references to species that have been studied, much about their behavior,
and details of methodology by which quantification has become possible
(5,
7,203-208).
Many birds migrate, and in all except the parasitic species
(209-213)
the behavioral sequence which is a part of the reproductive process is
commonly composed of territorial establishment and defense, nest building, courtship, mating, egg laying, incubation, and parental care. The
sequence probably is more elaborate than any encountered in the other
vertebrate phyla. Many factors such as seasonal and meteorological
changes, food, nesting sites, nesting materials, and especially interpersonal relationships influence this behavior (7), but agreement is general
that once the process starts at the beginning of the reproductive season,
a certain endocrine readiness must exist before the next step will be
taken.
The relationship of the hormones to migration is equivocal (208,
214-218).
Experimental analysis of the problem is difBcult, and conceptualization must be broad enough to cover the two sexes. Any theory