DEVELOPMEXT OF GEXITO-URIXARY ORGAXS 



1057 



The Miillerian duct l)e<rius as a slender cord lying jiaralkl to, and un the outer side ut', the 

 Wolffian duet. It becomes canalized and ojtens distally into the cloaca. After a time it i'usos 

 with its fellow mesially a short distance above the terminal aperture, and the conjoint tube is 

 bound together with the adjacent Wolffian ducts into a kind of stem called the genital cord. In 

 tile male the Miillerian duct never appears to di.scharire any function, and its useless relics are to 

 be traced in the sinus pocularis and hydatid of Morgagni ; but in the female it gives rise to nearly 

 the whole of the internal apparatus of generation ; its upper extremity, above the line of fusion 

 in the human subject, forming the oviiluct and its hydatid appendage, the conjoint tube develo|)- 

 iuL' the uterus and vagina. Variations in the point of fusion (jf the two ducts may lead to the 

 abnormality of a two-horned uterus, or even a double uteiiis and vagina. Exceptionally Miiller's 

 duct may firm a rudimentary uterus in the male. In .such cases the testes are well developed, 

 but the penis remains very small. 



Fig. 046.— Devi:lopment of the Urino-gexekative Organs, Male Type. 



(After Henle.j 



BODY OF TESTICLE 



GUBERNACULUM 



VAS DEFERENS 

 URETER 



VESICULA SEMINALIS 



SINUS POCULARIS 



EJACULATORY DUCT 



PROSTATE 



MEMBRANOUS URETHRA 



BULB 



PROSTATIC URETHRA 



CORPUS SPONGIOSUM 

 CORPUS CAVERNCSUM 



The external genitals are developed about the doacal outlet common to the genito-urinary 

 and intestinal canal:". The first change is the appearance of a genital eminence, the future clitoris 

 or i>enis, at the ventral extremity of the cloacal fi.ssure about the fifth or sixth week. A fortnitrht 

 later the cloaca is flivided by a transverse septum into two jiarts, a dorsal or anal, and a ventral or 

 uro-genital (uro-genital sinus); the se|itum it.self persisting as the perinf\?al Inidy in the female, 

 and the portion of the perin.-vum lying between the scrotum and anus in the male. Its ab.<ence 

 or incomplete development accounts for certain congenital malformations well known to teratolo- 

 <:i-ts. The uro-genital sinus next undergoes changes which give the external stain j) of sex. At 

 first the urethra ojiens into the sirms liehind the genital prominence. In the female this remains 

 permanent, the lips of the sinus expand into the labia niajora ; two ridges within the sinus, ex- 

 tending one on each side as high as the genital prominence, form the nymjilifc ; and a little .semi- 

 lunar fold at the entrance of the vaerina shows itself in the fifth month and becomes the hymen ; 

 67 



