STRUCTUKE OF THE PROSTATE. 407 



through the glandular substance. Over the greater part of the and super, 

 surface is an external stratum, forming a kind of capsule, which * 

 adheres to the fibrous sheath. Along the front and towards the 

 apex, the superficial part of the organ is composed of striated mus- 

 cular fibres, also disposed transversely, which are continued into 

 the constrictor urethras muscle between the layers of the triangular 

 ligament. 



Glandular substance. This is composed of a number of small Glands in 

 branched glands, which are embedded in the muscular stroma. ma sses: 

 There are three chief collections, a small one in the central lobe, 

 and a larger one in each lateral lobe. The ducts of the glands ducts open 

 vary in number from twelve to twenty, and open into the prostatic u "ethra? 

 part of the urethra (p. 413). 



Blood-vessels. The arteries are small, and are furnished by the Arteries, 

 inferior vesical and middle haemorrhoidal. The veins form a plexus 

 round the gland, which receives in front the dorsal vein of the 

 penis, and is continued behind into the plexus at the base of the 

 bladder. The plexus is situated between the fascial investment 

 and the proper capsule of the gland, and the vessels of the plexus 

 are specially large at the back of the pubis at the entry of the 

 dorsal vein of the penis. In old men these vessels may give rise 

 to considerable haemorrhage in the operation of lithotomy. 



The nerves are supplied from the pelvic plexus. The lymphatics Nerves, 

 of this body and of the vesiculse seminales are received into the Lymphatics, 

 glands by the side of the internal iliac artery. 



VESICUL^ SEMIXALES (fig. 151, e}. These vesicles are two mem- seminal 

 branous sacs, which serve as receptacles for, and probably secrete a vesicles ' 

 special fluid to mix with, the semen. They are placed at the base definition ; 

 of the bladder above the prostate, and diverge from one another so situation ; 

 as to limit laterally a triangular space in that situation : their form 

 and relations have been already described (p. 389). Though form ; 

 sacculated and bulged above, the vesicula becomes straight and 

 narrowed below (duct) ; and at the base of the prostate it blends 

 with the vas deferens to form the common seminal or ejaculatory 

 duct (0). 



The vesicula seminalis consists of a tube bent into a convoluted consist of a 

 form, so as to produce lateral sacs or poiiches, the bends of which are fo 

 bound together by fibrous tissue ; this cellular structure will be 

 shown by means of a cut into it. When the bends of the vesicle 

 are undone, as may be done by carefully dissecting away the 

 investing tissue, its formative tube, which is about the size of a 

 quill, measures from four to six inches in length, and ends above in 

 a closed extremity : connected with the tube at intervals, are lateral length and 

 blind csecal appendages (fig. 151). size * 



Structure. The wall of the seminal vesicle like the vas deferens Vesicle has 

 has an outer and inner layer of longitudinal muscle fibres with an Ub 

 intermediate circular layer, but the tubal muscular coat is thinner. 



Within the casing of the recto-vesical fascia, the vesiculae and a covering 

 vas deferentia are covered by a layer of transverse and longitudinal 

 plain muscular fibres. The transverse are the more superficial 



