428 ABDOMEN 



The ureteral orifices lie at the superior angles of the 

 trigone. They are small semilunar slits, and are frequently 

 connected together by a transverse bar of mucous mem- 

 brane (torus vesicalis) which covers a bar of muscle. Not 

 uncommonly a ridge of mucous membrane covering a muscular 

 band will be found connecting each ureter with the urethra. 

 Probes should be passed along the ureters to demonstrate 

 the obliquity with which the ducts pass through the bladder 

 wall. It will be found that each ureter runs through the 

 substance of the bladder wall for about 20 mm. (three- 

 quarters of an inch). This arrangement serves the purpose 

 of a valve which allows urine to pass easily into the bladder 

 but tends to prevent its backward flow. When the bladder 

 is distended the openings of the ureters are about 35 mm. 

 (an inch and a half) apart, and about the same distance 

 from the orifice of the urethra, but when the viscus is empty 

 and contracted the distance between the orifices is reduced 

 to about 25 mm. (one inch) in each case. 



The dissector should now investigate the relations of the 

 fundus of the bladder by palpation. Keeping one index finger 

 in the bladder and passing the other into the rectum, he will 

 find that he can distinguish the prostate below and around 

 the internal urethral orifice. Above the level of the prostate 

 he can feel the thick walls of the deferent ducts, one on 

 each side of the median plane, and more laterally he will 

 recognise the convoluted coils of the seminal vesicles. If he 

 passes his finger upwards, along the median plane, he will 

 find that the deferent ducts diverge, and that between 

 them the rectum and bladder lie in contact. The area in 

 which that contact occurs corresponds with the posterior part 

 of the trigone, and varies considerably in size. When the 

 bladder is empty the area is small or absent ; but it increases 

 considerably when the bladder is distended. 



Dissection. When the dissector has satisfied himself regard- 

 ing the relations of the base of the bladder and the possibility of 

 easily distinguishing them with the finger through the rectal 

 wall, he should introduce a blunt-pointed knife, or a pair of 

 scissors, through the internal urethral orifice into the urethra, 

 and lay the canal open by dividing its dorsal wall from the 

 bladder to the end of the penis. 



Urethra Virilis. The male urethra is the canal through 

 which the urine, the semen, and the secretions of the 

 seminal vesicles, the prostate and bulbo-urethral glands 



