1146 UROGENITAL SYSTEM. 
fused posterior parts, which at first open into the urogenital canal, give rise to the 
uterus and vagina. The manner in which the original position of the opening of the 
Miillerian ducts becomes shifted, by the shortening of the urogenital canal, so as to appear 
at the bottom of the urogenital fissure, has already been described. 
The vaginal portion of the fused Miillerian ducts is at first relatively very short, and at 
the point where it opens into the urogenital canal a slight fold appears, which is the 
future hymen. The vagina increases rapidly in length as its opening moves downwards 
towards the urogenital cleft. 
The Wolffian ducts and the mesonephros atrophy in the female, but traces of them are 
to be found in the longitudinal canal of the parovarium and paroophoron of the adult. In 
the foetus the Wolfhan duct can be traced along each side of the uterus as far as the 
upper end of the vagina. 
Prostate.—The elandular portion of the prostate arises as a series of solid out- 
growths from the epithelium of the urogenital canal during the third month. The. 
outgrowths, which are at first simple, become branched eral finally acquire a lumen. 
They are arranged in three groups—an upper and a lower dorsal group, and a ventral. 
The elands of the ventral group soon become reduced in number and often completely 
disappear. 
Cowper’s glands are also developed from the epithelium of the urogenital canal. 
The glands of Bartholin arise as outgrowths from the epithelium of the urogenital 
canal. 
External Genital Organs.—The external genital organs are developed in the 
region of the ectodermal cloacal fossa, and those of the male and female can only be 
distinguished from one another after the ninth week. The fossa is at first shallow, 
but soon, by the formation of prominent lateral boundaries, it becomes much deeper. 
These lateral eminences receive the name of outer genital or labio-scrotal folds, and 
enclose between them the genital eminence and the urogenital opening (Fig. 783). 
The urogenital opening is at this time a mesial cleft and its margins form a second 
pair of much smaller folds called the inner genital folds. The genital eminence which 
is situated at the upper or anterior end of the fossa, appears very early, even before 
the cloaca becomes divided into rectal and urogenital subdivisions. Its summit is 
somewhat enlarged, and its posterior surface presents a groove which leads into the 
urogenital opening. The genital eminence gives origin to the terminal portion of the 
clitoris i in the female and af the penis in the male, the enlarged extremity becoming the 
glans in each case. In the female the interval between outer genital folds yeconnes the 
‘urogenital cleft of the adult, the outer folds the labia majora, and the inner folds the 
labia minora. The groove on the posterior aspect of the clitoris becomes closed, but does 
not form a canal. In the male, on the other hand, the cloacal fossa becomes roofed over 
by the meeting together of its lateral boundaries to enclose a canal which becomes the 
spongy part of the urethra. The outer genital folds, meeting in a median raphe, form the 
scrotum. The groove on the posterior aspect of the genital eminence becomes by the 
fusion of its margitis the terminal portion of the male urethra. 
THE MAMMARY GLANDS. 
The mammary glands (mammee) or breasts are accessory organs connected with 
the female reproductive system. Each gland is situated in the superficial fascia 
covering the anterior aspect of the thorax ,and usually extends from the level of 
the second to that of the sixth rib. The hemispherical projection formed by the 
gland lies upon the superficial aspect of the pectoralis major and to a small extent 
upon the serratus magnus muscle. Near the summit of each mammary elevation, 
and usually at the level of the fourth rib, is placed the wart-like nipple (papilla 
mamimeze), which is pierced by the minute openings of the lactiferous ducts and 
surrounded by a coloured circular area called the areola. The skin covering the 
nipple is thrown into. numerous wrinkles, while on the areola there are many 
minute rounded projections due to the presence beneath of cutaneous glands. These 
have received the name of Montgomery's glands or glandule areolares, and are con- 
sidered to represent rudimentary portions of the mammary gland. The colour of 
the nipple and areola varies with the complexion of the individual, but in young 
subjects they are usually of a somewhat rosy-pink colour, which changes to a deep 
brown during the second and third months of first pregnancy. During pregnancy 
