£*•

EVOLUTION OF THE FOSTUS. 185
pounds ; on the other hand, cases are not rare in which
is twelve or fifteen.
the weight
The wolfian bodies are foetal organs, Fig. 66.
which are engaged in the important
process of forming the kidneys and tes
ticles. When this work is accomplished,
these forming organs disappear. 1.
Kidneys? 2. Ureters. 4. Excretory
duct of the wolfian body. 5, 5. Testicles,
which, after being formed here, beside
the kidneys, descend, pass out by the
same channels as are afterward occupied
by the spermatic cords, and are lodged
in the scrotum. The ovaries are formed
in the same manner, and at first the sex
can not be distinguished. The clitoris is
and there is a cleft
as large as the penis,
below in both sexes. In males, a seam
or raphe shows the place of this cleft. In
females the ovaries remain attached to
the uterus in the pelvis, and the cleft
remains open.
During
the first weeks of the evolution of the em
bryo in the uterus, it is nourished, as the young chicken
is, by the yolk of the egg.
CORPORA WOLFIANA.
But soon the villi of the
chorion gather into a compact mass, and become ad
herent to some portion of the uterus. There is formed
thus a placenta, made of two portions, the maternal
side, toward the walls of the uterus, and the foetal,
in which the vessels unite into two arteries and one
vein, which, with these envelopments, form the umbilical
cord, and commuuicate with the foetal heart. By this
means, at every pulsation of the heart, blood is sent
through the two umbilical arteries to the placenta. Here
the vessels branch out into capillaries, which mingle
with those of the maternal placenta, communicating
with the uterus. Through the membranous coats of