522 DISSECTION OF THE PELVIS. 



derived from the pelvic fascia, and is separated from that sheath by a 

 plexus of veins. 



Muscular tissue. The firm part of the gland consists of involuntary 

 muscular fibres, intermixed with elastic and fibrous tissues. The muscular 

 fibres are arranged circularly around the tube of the urethra : they are 

 continuous behind with the annular fibres of the bladder, and in front 

 with a thin layer of circular fibres around the membranous part of the 

 urethra. 



At the lower and outer parts the texture is looser and more spongy, 

 especially where the glands are situate, and the larger vessels enter (Roy. 

 Med. Chir. Trans., 1856). This arrangement will be better seen when 

 the urethra has been opened. 



Glandular structure. Small branched glands project from the tube of 



the urethra amongst the muscular fibres ; they form but a small part of 



the prostate, and are most numerous in the middle lobe. The final radicles 



.' of the ducts are surrounded by small sessile vesicles : on the exterior of 



the vesicles and ducts the bloodvessels ramify. Lining the interior of the 



~; tubes is an epithelium of the columnar kind. The ducts of the glands 



vary in number from twelve to twenty, and open into the prostatic part of 



.. the urethra (p. 527). 



Bloodvessels. The arteries are rather small, and are furnished by the 



j inferior vesical and middle hsemorrhoidal (p. 515). The veins form a 



plexus around the gland, which communicates in front with the dorsal 



vein of the penis, and behind with the venous plexus at the base of the 



I bladder. In old men this vascular intercommunication gives rise to con- 



. siderable hemorrhage in the operation of lithotomy. ~ 



The nerves are supplied by the hypogastric plexus. The lymphatics 

 of this body and of the vesiculae seminales are received into the glands 

 placed along the internal iliac artery. 



VESICUL^E SEMINALES (fig. 178, e). These vesicles are two membra- 

 nous sacs, which secrete a fluid to mix with the semen. They are placed 

 on the under part of the bladder behind the prostate, and diverge from 

 one another so as to limit laterally a triangular space in that situation : 

 their form and connections have been already described (p. 507). Though 

 sacculated and bulged behind, the vesicula becomes straight and narrowed 

 in front (duct d) ; and at the base of the prostate it blends with the vas 

 deferens to form the common seminal or ejaculatory duct (g). 



The vesicula seminalis consists, like the epididymis, of a tube bent into 

 a zigzag form, so as to produce lateral sacs or pouches, whose bends are 

 bound together by fibrous tissue ; this cell structure will be shown by 

 means of a cut into it. When the bends of the vesicle are undone, its 

 formative tube, which is about the size of a quill, measures from four to 

 six inches, and ends posteriorly in a closed extremity : connected with the 

 tube at intervals, are lateral caecal appendages (fig. 178). 



Structure. The wall of the seminal vesicle has the same number of 

 layers as the vas deferens (p. 483) ; but the muscular coat is thinner. 



Within the casing of the recto-vesical fascia, the vesiculae and vasa 

 deferentia are covered by a layer of transverse and longitudinal plain 

 muscular fibres. The transverse are the more superficial (the base of the 

 bladder being upwards), are strongest near the prostate, and act most on 

 the vasa deferentia. The longitudinal fibres, placed chiefly on the sides of 

 the vesiculae, are continued forwards with the common seminal ducts to 

 the urethra. (Med. Chir. Trans. 1856.) 



