526 DISSECTION OF THE PELVIS. 



apex reaches the prostate, and its base the ureters. Its boundaries may 

 be marked out by a line on each side from the urethra to the ureter, and 

 by a transverse one, behind, between the openings of the ureters. This 

 surface corresponds with the triangular space externally at the base of the 

 bladder, between the prostate in front and the vesicular and vasa deferentia 

 on the sides. Over it the mucous coat is more closely united to the fibrous 

 and muscular, so as to prevent the accidental folds occurring in the other 

 parts of the empty bladder. 



Dissection. The arrangement of the fleshy fibres of the ureters will 

 come into view on the removal of the mucous membrane from the lower 

 third of the bladder. 



Ending of the fibres of the ureters. As soon as the ureter pierces the 

 outer and middle coats of the bladder, its longitudinal fibres are thus dis- 

 posed : the more internal and strongest are directed transversely, and 

 join the corresponding fibres of the other urine tube ; whilst the remainder 

 are continued down over the triangular surface, and blend with the sub- 

 mucous layer. 



Bloodvessels and nerves. The source of the vesical arteries, and the 

 termination of the veins have been detailed (p. 515). The vessels are 

 disposed in greatest number about the base and neck of the bladder. 

 Most of the nerves distributed to the bladder, though supplied from the 

 pelvic plexus of the sympathetic (p. 519), are derived directly from the 

 spinal nerves. The lymphatics enter the glands by the side of the internal 

 iliac artery. 



THE URETHRA AND PENIS. 



URETHRA (fig. 181). The tube of the urethra extends from the neck 

 of the bladder to the end of the penis, and has an average length of about 

 eight inches ; but it is shorter by one inch during life (Thompson). It is 

 supported by the prostate, the triangular ligament, and the spongy struc- 

 ture of the penis. The tube is divided, as before said (p. 508), into a 

 prostatic, a membranous, and a spongy part. 



Dissection. To open the urethra, let the incision through the upper 

 part of the prostate be continued onwards to the extremity along the line 

 of union of the urethral canal with the body of the penis. 



The prostatic part (fig. 181) is nearer the upper than the lower surface 

 of the muscular mass surrounding it. It is one inch and a quarter in 

 length, and is altogether the widest portion of the urethral canal. Its 

 form is spindle-shaped, for it is larger in the middle than at either end. 

 Its transverse measurement at the neck of the bladder is a quarter of an 

 inch ; at its centre a line or two more ; and at the front rather less than 

 at the back. 



Separating this part of the passage from the bladder is the eminence of 

 the uvula vesicae with its slight ridge. In front of this is a central longi- 

 tudinal eminence of the mucous lining (d), about three-quarters of an inch 

 in length, and larger behind than before, which is prolonged anteriorly 

 towards the membranous part of the canal, and is named crest of the 

 urethra (veru montanum, caput gallinaginis) : it is formed like the uvula 

 by a bundle of the submucous muscular and fibrous tissue. In that crest 

 of the mucous membrane, near its posterior extremity, is a slight hollow 

 (e) named vesicula prostatica or sinus pocularis. 



The vesicnla prostatica or utricle (fig. 180, g) is directed backwards 



