THE EXTERNAL GENITALIA 



233 



Female. A deep groove appears about the base of the phallus separating it 

 from the genital tubercle, which becomes a circular swelling (Fig. 229). From the 

 swelling differentiates (i) cranially, the mons veneris; (2) laterally, the right and 

 left labia majora; (3) caudally, the posterior commissure of the labia majora. 

 The glans of the phallus forms the glans clitoris of the female. On the anal sur- 

 face of the phallus beginning at the coronary sulcus the primitive urogenital open- 

 ing closes distally, forming the urethral groove. Proximally it remains open, as 



FIG. 229. Four stages in the development of the female external genitalia (Tourneux in Heisler). 

 i, clitoris; 2, glans clitoris; 3, urogenital aperture on each side of which are the labia minora (7); 4, 

 labia majora; 5, anus; 5, coccygeal eminence; 7, labia minora. 



the definitive urogenital opening near the base of the phallus. The lips of this 

 groove and opening enlarge and become the labia minora. The cranial surface 

 of the phallus forms a fold, the prepucium, which, however, is not the homologue 

 of the male fore-skin. This in the female is represented by a ring-like rudiment 

 at the base of the glans clitoris. 



Male. The phallus grows rapidly at its base so that the glans and primitive 

 urogenital opening are carried some distance from the anus (Fig. 230). A cylin- 



