416 DEVELOPMENT OF ORGANS IN MAMMALIA. [CHAP. 



tary tract becomes partially constricted off from the 



ventral, which then forms a urinogenital sinus (Fig. 140 



ug). In the course of development the urinogenital 



FIG. 140. 



DIAGRAM OF THE URINOGENITAL ORGANS OF A MAMMAL AT 

 AN EARLY STAGE. (After Allen Thomson ; from Quain's 

 Anatomy.) 

 The parts are seen chiefly in profile, but the Mlillerian and 



Wolffian ducts are seen from the front. 



3. ureter; 4. urinary bladder; 5. urachus ; ot. genital ridge 

 (ovary or testis) ; W. left Wolffian body ; x. part at apex 

 from which coni vasculosi are afterwards developed ; w. 

 Wolffian duct ; m. Miillerian duct ; gc. genital cord consist- 

 ing of Wolffian and Miillerian ducts bound up in a common 

 sheath ; i. rectum ; ug. urinogenital sinus ; cp. elevation 

 which becomes the clitoris or penis ; Is. ridge from which the 

 labia majora or scrotum are developed. 



