686 A MANUAL OF ANATOMY 



Development of the Testis and its Excretory Apparatus. — The embryonic 

 rudiments pertaining to the development of the testis are as follows: 



Genital ridge. 

 Sex-cords. Anterior tubules of the meso- 



Rete-cords. nephros, or Wolffian body. 



Wolffian duct. 



The cells of the germinal epithelium of the sex-gland region of the genital 

 ridge which invade the mesoderm are, as stated, small epithelial cells and 

 large sexual cells, and they are arranged as cylindrical columns, which, as 

 stated, are known as the sex-cords. These cords become separated from the 

 epithelium of the genital ridge when the tunica albuginea of the testis is 

 formed from connective tissue derived from ' the basal nuclei of the sex- 

 cords.' They are broken up into spherical masses which, like the sex-cords, 

 consist of small epithelial cells and large sexual cells. These masses become 

 hollow, and, after undergoing elongation, they give rise to the secreting 

 seminiferous tubules. The sexual cells of the masses become spermatogonia, 

 or primordial sperm-cells, from which the spermatozoa are derived, whilst 

 the small epithelial cells are probably transformed into the cells of Sertoli. 

 For spermatogenesis, or the formation of spermatozoa, see Index. 



The excretory tubules (tubuli recti and rete testis) are usually regarded as 

 being developed from the anterior or sexual tubules of the mesonephros, or 

 Wolffian body. From the epithelium of the Malpighian corpuscles of these 

 tubules solid cords of cells, called the rete-cords, grow into the developing 

 testis. These cords become tubular, and they give off branches which acquire 

 connections with the secreting seminiferous tubules. In this manner the 

 tubuli recti and rete testis are formed. The vasa efferentia are developed 

 from the anterior or sexual tubules of the Wolffian body. 



Another view is that the rete-cords arise from the cells of the germinal 

 epithelium over the anterior or rete-region of the genital ridge, being serially 

 homologous with the sex-cords. The rete-cords are at first solid, but subse- 

 quently acquire a lumen. They extend posteriorly into the proper glandular 

 substance, formed by the sex-cords. As they do so, they give off branches, 

 each of which passes to one of the spherical masses into which the sex-cords 

 are broken up. Within this mass it becomes continuous with a secreting 

 seminiferous tubule. 



The proximal ends of the rete-cords become detached from the epithelium 

 of the rete-region of the genital ridge. They then come into close contact 

 with the capsules of Bowman of the Malpighian corpuscles belonging to the 

 anterior or sexual tubules of the mesonephros or Wolffian body, which tubules 

 give rise to the vasa efferentia of the testis. The contact may be direct, 

 or through means of evaginations of the walls of Bowman's capsules. In either 

 case fusion takes place, and the proximal ends of the rete-cords (rete-tubules 

 open into the capsules of Bowman, and become continuous with the anterior 

 or sexual tubules (vasa efferentia of the testis) of the mesonephros. These 

 mesonephric tubules open into the Wolffian duct, which gives rise to the 

 epididymis, vas deferens, and common ejaculatory duct. 



The convoluted canal of the epididymis, the vas deferens, and the common 

 ejaculatory duct are developed from the Wolffian duct. The vesicula seminalis 

 is formed as a blind diverticulum of the caudal part of the Wolffian duct; 

 and the vas aberrans is a slender diverticulum of that portion of the Wolffian 

 duct which forms the globus minor, or tail, of the epididymis. 



Summary. — The testis, genetically considered, consists of (i) secreting 

 seminiferous tubules and seminal cells, and (2) excretory tubules. The 

 secreting seminiferous tubules and their seminal cells are developed from 

 the sex-cords of that portion of the germinal epitheUum which covers the 

 sex-gland region of the genital ridge. The tubuli recti and rete testis are de- 

 veloped from the epithelium of the Malpighian corpuscles of the anterior or 

 sexual tubules of the mesonephros, or Wolffian body, which covers the anterior 

 or scA-Ma/^/rt«rfy<^gjow, or from the germinal epithelium of the rete-region of the 

 genital ridge. The vasa efferentia are developed from the anterior or sexual 

 tubules of the mesonephros or \\'olffian body. The epididymis, vas deferens, 



