THE ABDOMEN 



669 



After passing through the internal abdominal ring it hooks round the 

 outer side ot the deep epigastric artery, and, having crossed the 

 external iliac vessels from without inwards, it dips down on the 

 inner side of the external iliac vein, and so enters the pelvis under 

 cover of the peritoneum, where it will be afterwards described. 

 The vas deferens in its natural state measures about i foot in length, 

 but when straightened it attains a length of from i^ to 2 feet. 



Mucosa and 

 Columnar Epithelium 



" Iter Longitudinal 

 Muscular Fibres 



Inner Longitudinal 

 Muscular Fibres 



Middle Circular Muscular 

 Fibres 



Fig. 289. 



-Transverse Section of the Vas Deferens, showing its 

 Minute Structure. 



Structure ol the Vas Deferens. — The vas deferens has a very thick wall, 

 and feels like a piece of whip cord. Its outer coat consists of fibrous tissue. 

 Within this there is a thick muscular coat composed of plain muscular 

 tissue, which is arranged in three la^-ers — an outer longitudinal, a middle 

 circular (both of which are thick), and an inner thin longitudinal layer. Within 

 the muscular coat is the mucosa, which is covered by non-ciliated columnar 

 epithelium. 



Development. — From the lower part of the Wolffian duct. 



The artery of the vas deferens, or deferential artery, is usually a 

 branch of the superior vesical of the internal iliac, though it may 

 arise from the inferior vesical, and it diN-ides into a descending 

 and an ascending branch. The descending branch passes downwards 

 to supply the lower part of the vas deferens and the vesicula 

 seminalis. The ascending branch accompanies the vas deferens 

 through the inguinal canal to the testis, suppling the vas deferens, 

 and giving a few tungs to the globus minor of the epididymis, in 

 which latter situation it anastomoses with the epidid\Tnal branch 



