872 A MANUAL OF ANATOMY 



epithelium which covers the mucous membrane is of the columnar 

 non-ciliated variety. 



Blood-supply — Arteries. — These are derived from the inferior 

 vesical, the middle hemorrhoidal, the descending branch of the 

 deferential artery, and the intrapelvic portion of the sciatic. 



The veins are fairly large and numerous, and are disposed in a 

 plexiform manner. They communicate with the prostatico-vesical 

 plexus. 



Lymphatics. — ^These go to the internal iliac glands. 



Nerves. — ^These are derived from the pelvic plexus. 



Development. — Each vesicula seminalis is developed as a diverticulum 

 from the posterior or caudal part of the Wolffian duct, from which the vas 

 deferens originates. 



Structure of the Common Ejaculatory Ducts. 



The wall of each duct is composed of three layers, as follows : an 

 outer fibrous layer, which is very delicate ; a middle muscular 

 layer, composed of an outer circular and inner longitudinal stratum ; 

 and an inner mucous layer, lined by columnar non-ciliated epithe- 

 lium. 



Development. — Each duct is developed from the posterior or caudal part 

 of the Wolffian duct. 



Structure of the Prostate Gland. 



The prostate gland is encased in a strong capsule, which is formed 

 principally by the visceral portion of the pelvic fascia, and partly 

 by the parietal pelvic fascia, in the following manner : the anterior 

 wall of the capsule is formed by the prostatic lamina, and the pos- 

 terior wall by the recto-prostatic lamina, of the visceral portion 

 of the pelvic fascia ; and on either side the capsule is joined 

 by the corresponding half of the deep or postero-superior layer 

 of the triangular ligament of the urethra (which is formed by 

 the parietal pelvic fascia), after it has passed backwards over the 

 anterior border of the corresponding levator ani muscle. The 

 capsule has a material influence in fixing the prostate gland in its 

 position. Within this capsule there is the prostatic plexus of veins, 

 and within this plexus there is another special capsule, composed 

 of fibrous tissue, which immediately surrounds the glandular sub- 

 stance. The prostatic venous plexus is thus enclosed between the 

 two capsules. The substance of the gland is composed of two 

 elements — muscular and glandular. The muscular tissue, which is 

 of the plain variety, is arranged as (i) an external, partly longi- 

 tudinal and partly transverse, layer, which lies beneath the special 

 fibrous capsule, and (2) an internal circular layer, which surrounds 

 the prostatic urethra, being continuous above with the fibres ol 

 the sphincter vesicae, and below with those around the membranous 

 portion of the urethra. Between these two layers the muscular 

 fibres pervade the gland in a decussating manner, so as to con- 

 struct a muscular reticulum, the meshes of which contain the 



