DEVELOPMENT OF THE UROGENITAL ORGANS. 1145 
cells to form the future follicles (p. 1125). It is extremely doubtful if any new ova arise 
after birth. 
Generative Ducts.—As has been already stated, the male ducts arise from the 
Wolffian and the female from the Millerian ducts of the embryo. Both sexes at first 
possess well-developed Wolffian and Miilerian ducts, which are arranged i in a very definite 
manner. The Wolffian ducts communicating dir ectly with the tubules of the mesonephr Os 
lie at first parallel to, and at a considerable distance from one another. As they pass 
backwards to the caudal end of the embryo they approach one another, and each becomes 
enclosed in a fold of peritoneum called the plica urogenitalis. The ducts, which soon 
become closely approximated to 
each other, are embedded in a cord- 
like mass of connective tissue, to 
which- the term genital cord is 
applied. They finally open into 
the lower part of the anterior 
subdivision of the cloaca. 
The Miillerian ducts, opening 
freely into the body cavity at their 
cephalic ends, lie to the outer side 
of the Wolfhan ducts. As they 
are traced caudally they cross the 
Wolffian ducts and enter the genital 
cord, within which they unite and 
form a canal, which occupies the 
mesial plane, and opens into the 
lower part of the anterior sub- 
division of the cloaca, between the 
Wolfhan ducts. The manner in 
which the ureters become separated a 
from the Wolfhan ducts has already Fic. 783.—THE DEVELOPMENT OF THE EXTERNAL GENITAL 
been described. ORGANS. From the models by Professor Ecker. 
Ducts in the Male.— The A. Slit-like ectodérmal cloaca 0, bounded on each side by an 
i = >} d 
seminal tubules of the testis become elevation, e. 
connected with the Wolthan duct B. The genital eminence g, lies anterior to the opening of the 
by a fusion of the anterior canals fossa ; s indicates the inner genital fold, to the outer side of 
: : yhich the labio-scrotal fold is seen. 
Bel “the mesonephros Athenee which the labio-scrotal fold is seen 
seminal tubules At the place C. Female—after complete separation of the rectum from the 
i 2 e urogenital portion of the cloacal fossa. The urogenital por- 
where this fusion USES) the rete tion of the fossa is bounded on each side by the labium majus 
testis and tubuli recti are formed. and the labium minus. 
The ee Be definitely estab- p, Male—closing in of the urogenital portion of the ectodermal 
lished in the third month. The cloaca and of the groove on the sexual eminence to form the 
number of tubules taking part spongy portion of the urethra. Origin of the penis and 
varies considerably, but  corre- Soom 
sponds to the number of vasa /- Female—the urogenital portion of the ectodermal cloaca 
af ; remains open and forms the greater part of the urogenital 
efferentia found in the adult. The clett Leh adult 2 p eae 
connecting tubules becoming much ae A SS Raphe: 
convoluted, just as they jom the e. Wall of cloacal fossa. s. Imer genital fold in B, and sero- 
7 a : : . Genital eminence or glans. tum or labio-serotal fold in D. 
Wolftian duct, form the coni vas- ie 2 ‘ =e 
5) 1. Lower limb. Sp.c. Umbilical cord. 
] The 1 l.maj. Labium majus. canals 
culosi. 1e@ Canal O € epi 
é 5 a 6 E min. Labium minus. ug. Urogenital portion of cloaca or 
didymis is directly formed from o. Opening of cloaca. opening into it. 
the anterior part of the Wolfhan 
duct, and the vas deferens from the more posterior portion. The ductuli aberrantes 
and the rudimentary tubules of the organ of Giraldés are to be looked upon as per- 
sistent tubules, of a more posterior portion of the Wolffian body, which have failed to 
become connected with the tubules of the testis. The seminal vesicles which arise in 
the third month are developed as evaginations from the Wolffian ducts, near their caudal 
extremities. From the part of the cloaca into which the Wolffian ducts open the prostatic 
urethra of the adult is derived. The Miillerian ducts atrophy in the male embryo, but 
the hydatids of the epididymis and of the testis are rudimentary remains of their anterior 
portions, while the sinus pocularis represents the lower fused portions which, in the 
embryo, occupy the genital cord. 
Ducts in the Female.—The Miillerian ducts in the female retain their openings 
into the body cavity, and their anterior portions become the Fallopian tubes, Their 
