he theory
that there are two opposing kinds of secretion poured into the blood in
unusual degree during pregnancy: one contracting the vessels, the other
dilating them, one or the other sometimes gaining the upper hand.
Suprarenal extract, when administered, has a vaso-constricting influence,
and thyroid extract a vasodilating influence; it may be surmised that
within the body these glands perform similar functions.[178]

The important part played by the thyroid gland is indicated by its marked
activity at the very beginning of pregnancy. We may probably associate the
general tendency to vasodilatation during early pregnancy with the
tendency to goitre; Freund found an increase of the thyroid in 45 per
cent. of 50 cases. The thyroid belongs to the same class of ductless
glands as the ovary, and, as Bland Sutton and others have insisted, the
analogies between the thyroid and the ovary are very numerous and
significant. It may be added that in recent years Armand Gautier has noted
the importance of the thyroid in elaborating nucleo-proteids containing
arsenic and iodine, which are poured into the circulation during
menstruation and pregnancy. The whole metabolism of the body is indeed
affected, and during the latter part of pregnancy study of the ingesta and
egesta has shown that a storage of nitrogen and even of water is taking
place.[179] The woman, as Pinard puts it, forms the child out of her own
flesh, not merely out of her food; the individual is being sacrificed to
the species.

The changes in the nervous system of the pregnant woman correspond to
those in the vascular system. There is the same increase of activity, a
heightening of tension. Bruno Wolff, from experiments on bitches,
concluded that the central nervous system in women is probably more easily
excited in the pregnant than in the non-pregnant state, though he was not
prepared to call this cerebral excitability "specific."[180] Direct
observations on pregnant women have shown, without doubt, a heightened
nervous irritability. Reflex action generally is increased. Neumann
investigated the knee-jerk in 500 women during pregnancy, labor, and the
puerperium, and in a large number found that there was a progressive
exaggeration with the advance of pregnancy, little or no change being
observed in the early months; sometimes when no change was observed during
pregnancy the knee-jerk still increased during labor, reaching its maximum
at the moment of the expuls