THE URETHRA. 389 



and the base surrounds the neck of the bladder and the common 

 seminal ducts. 



The prostate is enveloped by a sheath obtained from the recto- itiscon- 

 vesical fascia (p. 349), and the prostatic plexus of veins surrounds 

 it. Through the gland the urethra takes its course to the perineum ; 

 and the common seminal ducts pierce it obliquely to open into the 

 urethra, as will be seen in the examination of the organ after its 

 removal from the body. The size of the prostate varies much ; size may 

 and in old men it may acquire a considerable magnitude. 



The VESICULA SEMINALES (fig. 145, #) are two small sacculated Seminal 

 bodies, each about two inches long, between the base of the bladder vesicles : 

 and the rectum. Each is pyramidal in form, and has the larger their 

 end turned upwards towards the ureter, while the smaller touches 

 the prostate. Along the inner side is the vas deferens. At the 

 prostate gland the vesiculse approach one another, only the vasa 

 deferentia intervening ; but higher up they diverge, and enclose a 

 triangular space at the base of the Madder. The vesiculse are and sheath, 

 contained in a membranous sheath, which is derived from the 

 recto-vesical fascia, and is lined by involuntary muscular fibres. 



The VAS DEFERENS, or the excretory duct of the testis (figs. 144 Vas 

 and 145, /), in its course to the urethra enters the abdomen by the de 

 internal abdominal ring, and crossing the obliterated hypogastric 

 artery, is directed downwards along the hinder part of the bladder 

 to the base of the prostate, where it forms the common seminal or course ; 

 ejaculatory duct by joining with the duct from the vesicula unites with 

 seminalis. The position of this tube to the external iliac artery yg^cuia! 11 

 has been noticed ; on the bladder it passes internal to the ureter 

 and the vesicula of the same side. By the side of the vesicula the 

 duct is much enlarged, and is sacculated. 



Dissection. The prostate being cleaned the membranous and 

 spongy parts of the urethra will now be cleanly laid bare on the 

 left side but not opened. 



The URETHRA is the excretory passage for the urine and semen Urethra: 

 (fig. 144), and reaches from the bladder to the end of the penis. 

 In length it measures about eight inches, and presents one or two length ; 

 curves according to the state of the penis. At first the canal is curves ; 

 directed downwards and forwards through the triangular ligament 

 of the perineum to the root of the penis, forming a large curve with 

 the concavity to the pubis. Thence to its termination the urethra 

 is contained in the penis ; and while this body remains pendent 

 the canal forms a second bend with the concavity downwards ; but 

 if the penis is raised the tube makes but one curve. The canal is division, 

 divided into three parts prostatic, membranous, and spongy. 



The prostatic part (6) is contained in the prostate gland. Its Prostatic. 

 length is about one inch and a quarter, and in the erect posture of 

 the body it descends nearly vertically to the triangular ligament. 



The membranous part (c), about three-quarters of an inch long, Mem- 

 intervenes between the apex of the prostate and the lower surface branous : 

 of the triangular ligament. It slants forwards in the erect posture 

 to the lower part of the triangular ligament ; and as the bulb of 



