he growing fetus, as it is the job
par excellence of the thyroid to render innocuous these poisons.
Of adrenal insufficiency, failure of the adrenals to hypertrophy
sufficiently in pregnancy, little is known. Possibly the corpus
luteum, the endocrine formed of the torn egg nest in the ovary, makes
up for any deficiency in this respect. For there is the most curious
resemblance imaginable between the cells of the adrenal cortex and
those of the corpus luteum, some day to be completely explained.

THE PLACENTAL GLAND

The placenta, an organ and gland of internal secretion newly formed in
the uterus, when the fertilized ovum successfully imbeds itself within
it, must be considered in any analysis of the transfigurations of
child-bearing. Born with the pregnancy, its life is terminated with
the pregnancy, for it is expelled in labor as the after-birth. Its
importance and function as a gland of internal secretion has become
known only recently. Many still doubt and question the accordance of
that rank to it. But feeding experiments with it, in various endocrine
disturbances in human beings, have proved its right to the title.

The placenta is created by the fusion of the topmost enlarged cells
of the uterine surface and the most advanced cells constituting
the vanguard of the growing and multiplying ovum. These front line
invaders interact with the cells in contact with them to make a new
organ which serves as lung, stomach and kidney for the embryo, since
it is the medium of exchange of oxygen, foodstuffs and waste products
between the blood of the mother and the blood of the embryo.
Ultimately it acts, too, as a gland of internal secretion, influencing
the internal secretions of the mother, and also those of the embryo.

Settlement of the fertilized ovum in the womb introduces into the
system new secretions, new substances which are partly male in origin,
since the ovum contains within it the substance of the male sperm
which has penetrated it. This masculine element causes a rearrangement
of the balance of power between the endocrines towards the side of
masculinity. They push down the pan of the scale to inhibit the
post-pituitary. So menstruation, the menstrual wave which follows the
increasing tide of post-pituitary secretion, is postponed. For ten
lunar months, not another ovum breaks through the covering of the
ovary, and the uterus is left undisturbed. The placental secretion
plays a most important role as brake