1214 



SPLANCHNOLOGY 



the genital tubercle grow backward as the genital swellings, which ultimately form 

 the labia majora; the tubercle itself becomes the mons pubis. The labia minora 

 arise by the continued growth of the lips of the groove on the under surface of the 

 phallus; the remainder of the phallus forms the clitoris. 



Umbilical cord 

 'Genital tubercle 

 Hind-limb 

 Cloaca, 



Tail 



Genital tubercle 

 Labium majus 

 Labium minus 

 ; Urogenital 

 " membrane 



Gflans penis 



Scrotal swelling 



Edge of groove on phallus 



Opening ofuroyenital sinus 



Perineum 



Anus 



Glans clitoridif 

 Labium majus 

 Labium minus 

 Opening of 

 urogenital sinus 



Perineum 



.:.: '<, ~ A IIUH 



Glans penis 

 Cavernous urethra 



Anus 



Prepuce 

 Glans clitoridit 



Labium majus 

 Labium minus 



Vestibule 

 Vaginal orifice 



Anus 



Fia. 1119. Stages in the development of the external sexual organs in the male and female. (Drawn from the 



Ecker-Ziegler models.) 



In the male the early changes are similar, but the pelvic portion of the cloaca 

 undergoes much greater development, pushing before it the phallic portion. The 

 genital swellings extend around between the pelvic portion and the anus, and form a 

 scrotal area; during the changes associated with the descent of the testes this area 

 is drawn out to form the scrotal sacs. The penis is developed from the phallus. 

 As in the female, the urogenital membrane undergoes absorption, forming a channel 

 on the under surface of the phallus; this channel extends only as far forward as the 

 corona glandis. 



The corpora cavernosa of the penis (or clitoris) and of the urethra arise from the 



