THE EXTERNAL GENITALIA ' 237 



testis and the vagina masculina. The mesonephric duct is functional, its deriva- 

 tives being the ductus epididymis, the ductus deferens, the ampuUa and seminal 

 vesicle. The collecting tubules of the mesonephros form the ductuli efferentia 

 of the epididymis and the vestigial paradidymis. The phallus enlarges and be- 

 comes the penis, into which extends a portion of the urogenital sinus as the ure- 

 thra. The genital tubercle disappears and the scrotum is developed as a new- 

 structure, into the vaginal sacs of which the testes descend. 



Female (Fig. 231 B). — The genital gland becomes the ovary. The meso- 

 nephric duct degenerates except for the vestigial Gartner's canal. Two groups of 

 mesonephric tubules persist, a cranial group united with the rete ovarii constitut- 

 ing the rudimentary epoophoron, the homologue of the epididymis, a caudal group 

 forming the paroophoron, comparable to the paradidymis. The Muellerian ducts 

 become the functional female ducts. Their lower ends fuse and with their middle 

 portions form the vagina and uterus. Their upper portions persist as the 

 paired uterine tubes. The phallus remains small and becomes the clitoris, the 

 open lips of the urethral groove form the labia minora, and the genital tubercle 

 constitutes the mons veneris and the paired labia majora of the vulva. The ovar- 

 ies descend only into the true pelvis but the Kg. ovarii and the round ligament of 

 the uterus are the homologues of the gubernaculum testis. 



Hermaphroditism. — True hermaphroditism consists in the development and 

 persistence of both testes and ovaries in the same individual. It is of rare oc- 

 currence in man, is not uncommon in the lower vertebrates, and is the normal 

 condition in some invertebrates (earth worms, snails, etc.). In cases of human 

 hermaphroditism of this type the secondary sexual characters are usually inter- 

 mediate between the male and female, tending now one way now the other. The 

 external genitalia show a small penis with hypospadias, cryptorchism, or small 

 vaginal opening. 



False hermaphroditism is characterized by the presence of genital glands of 

 one sex in an individual which exhibits more or less marked secondary characters 

 and external genitalia of the opposite sex. In masculine hermaphroditism an in- 

 dividual possesses testicles, but the external genitals and secondary sexual char- 

 acters are like those of the female. In feminine hermaphroditism ovaries are 

 present, but the other sexual characters are male. The cause of hermaphroditism 

 is unknown. 



