404 



HISTORY OF THE HUMAN BODY 



At about this point, however, sexual differences begin to 

 appear, as may be seen by a comparison of the remaining 

 figures. The female organs, which remain nearer the embry- 

 onal condition, are not essentially different, save in propor- 

 tions, from the last stage common to both. The genital cleft 

 remains open, forming the introitus vagina, into which empty 

 the united Miillerian ducts (uterus) and the two ureters. The 

 genital folds form the corpora cavernosa (labia minor a or 



a 



FIG. 114. Development of the external genitals in Man. 



(a) and (b) Indifferent stages, (c) Early stage of the male organs, (d) Early 

 stage of the female organs. 



g, genital turbercle; c, genital folds; h, genital ridges; r, genital cleft; ra, anus; 

 p, perinaeum. 



nymphce) and the free tubercle itself forms the clitoris. The 

 external lips of the cloaca, the lateral genital ridges, form the 

 greater labia (labia major a). 



In the male the genital tubercle develops into the glans and 

 corpus cavernosum urethra [corpus spongiosum], and the 

 genital folds become the corpora cavernosa penis. By the 

 fusion of these latter the groove becomes converted into the 

 uro-genital canal, which becomes continuous with the urethra, 



