220 



UROGENITAL SYSTEM 



glands show two characters which mark them as testes: (i) The occurrence of 

 branched anastomosing cords of cells, the testis cords; (2) the occurrence between 

 epithelium and testis cords of a layer of tissue, the anlage of the tunica albuginea 

 (Fig. 218). According to Felix, the testis cords are developed suddenly from the 

 loose inner epithelial mass by a condensation of its cells. The cords converge and 

 grow smaller towards the mesorchium, where there is formed the undivided epi- 

 thelial anlage of the rete testis. Two or three layers of loosely arranged cells 

 between the testis cords and the epithelium constitute the anlage of the tunica 

 albuginea. According to Allen (Amer. Jour. Anat., vol. 3, 1904), the testis cords 

 are formed as active ingrowths of cords of cells from the epithelium. 



Mesentery 



Mesonephrfc 

 tubule 



■ 'if. — Mesotiephric 

 duct 



%— Muellerian 

 duct 



Intermediate cord 



Testis cord 



Epithelium ■ 

 Tunica albuginea. 



Fig. 218. — Transverse section through the left testis and mesonephros of a 20 mm. embryo. X 250. 



The testis cords soon become rounded and are marked off by connective 

 tissue sheaths from the intermediate cords, columns of undifferentiated tissue 

 which lie between them (Fig. 219). Toward the rete testis the sheaths of the 

 testis cords unite to form the anlage of the mediastinum testis. The testis cords 

 are composed chiefly of indifferent cells with a few larger genital cells. The cells 

 gradually arrange themselves radially about the inside of the connective tissue 

 sheath as a many-layered epithelium in which during the seventh month a lumen 

 appears. The lumina appear in the peripheral ends of the testis cords and ex- 

 tending toward the rete testis meet lumina which have formed there. Thus the 

 solid cords of both are converted into tubules. The distal portions of the testis 



