THE ORGANS OF THE MIDDLE GERM-LAYER. 



397 



In its last stages the descent in the female is accomplished in 

 a manner different from that in the male. For instead of advancing 

 like the testes toward the inguinal region, the ovaries, when the 

 development is normal, sink down instead into the true pelvis. Here 

 they are enclosed between bladder and rectum in the broad ligament, 

 which is developed out of the peritoneal folds, and in which originally 

 the primitive kidneys, the ovaries, and the Mullerian ducts are 

 imbedded. 



Naturally the round ligament cannot be of influence during this 

 last stage of the descent in the female, because it can exercise a 

 traction only in the direction of the inguinal region, where it is 

 attached. The descent into the true pelvis seems rather to be due to 

 the conversion of the lower region of the Mullerian ducts into the 

 uterus. At any rate, the ovaries are joined to the uterus by means 

 of a firm cord of connective tissue, 

 the ligamentum ovarii. 



In rare cases in the female the 

 ovaries can continue to change their 

 position in a manner corresponding 

 to that in the male. They migrate 

 then toward the inguinal region up 

 to the entrance into the processus 

 vaginalis (diverticulum Nuckii); oc- 

 casionally they here cease to advance, 

 but sometimes they enter farther into 

 the abdominal wall through the in- 

 guinal canal; indeed, as has been observed in several instances, they 

 can pass quite through the wall of the abdomen and at last imbed 

 themselves in the labia majora. The latter then acquire a great 

 similarity to the scrotum of the male. 



Fig. 223. Cross sectioa through the geni- 

 tal cord, after TOUKNEUX ET LEGAY. 



The cross section shows the fusion of the 

 Mullerian ducts (mg) ; ug, mesonephric 

 ducts. 



(i) The Development of the External Sexual Organs. 



The section which deals with the urinary and sexual organs is 

 really the most suitable place at which to introduce the development 

 of the external sexual organs, notwithstanding they do not arise 

 from the middle germ -layer, but in part from the outer and in part 

 from the inner germ-layer. In order to give an exhaustive account 

 of them, we must go back to rather early stages of development 

 to the time when in the embryo the Wolman and Mullerian ducts 

 are established. Having first arisen in the most anterior part cf the 



