214 



THE UROGENITAL SYSTEM 



testis to the tunica albuginea. The latter becomes a relatively thick layer in the 

 adult testis and is so called because of its whitish appearance. 



Anomalies. — The testis may be congenitally absent; the glands may be fused; or 

 they may fail to descend into the scrotum (cryptorchism) . Duplication of the testis is 



The Differentiation of the Ovary.— The primitive ovary, Kke the testis, 

 consists of an inner epithelial mass bounded by the parent peritoneal epithehum. 

 The ovarian characters appear much more slowly than in the testis. In fetuses 

 of 50 to 80 mm. (C H) the inner epithehal mass, composed of indifferent cells 

 and primitive genital cells, becomes less dense centrally and bulges into the 

 mesovarium (Fig. 227). There may be distinguished a dense, outer cortex beneath 



Tubules of mesonephros 

 {Paroophoron) 



Uterine {MiA- 

 lerian) tube 



Genital cells 



Medulla 



Epithelium - 

 Cortex . 



Fig. 227. — Section of an ovary from a 65 mm. himian fetus. X 44-. 



the epithelium, a clearer medullary zone containing large genital cells, and a 

 dense, cellular anlage in the mesovarium, the primitive rete ovarii, which is the 

 homologue of the rete testis. No epithelial cords and no tunica albuginea are 

 developed at this stage, as in the testis. Later, three important changes take place: 

 (1) There is an ingrowth of connective tissue and blood vessels from the hilus, 

 resulting in the formation of a mediastinum and of septula. (2) Most of the 

 cells derived from the inner epithehal mass are transformed into young cva, 

 the process extending from the rete ovarii peripherally (Fig. 227). (3) In fetuses 

 of from 80 to 180 mm. (C R) length the ovary grows rapidly, owing to the 

 formation of a new peripheral zone of cells, perhaps derived in part from the 

 peritoneal epithelium. At the end of this period the septulae line the epithehum 

 with a fibrous sheath, the anlage of the tunica albuginea. Hereafter, although 



