THE ABDOMEN 855 



end it is rather wider than at the lower end. Its diameter at the 

 centre, which is the widest part of the entire canal, is rather more 

 than \ inch ; at the upper or vesical end it is rather less than 

 this ; and at the lower end it is still less. This portion of the 

 urethra, though surrounded by the prostate gland, is the most 

 dilatable part of the whole canal. Close to the neck of the bladder, 

 however, it usually offers some resistance to the passage of an 

 instrument. Its walls are anterior and posterior, the latter being 

 often spoken of as the floor. These walls are in contact with each 

 other, except during the passage of fluid, and the mucous membrane 

 is thrown into longitudinal folds. The posterior wall presents along 

 the middle line a prominent narrow elevation of the mucous meni- 

 brane, called the crest. The other names by which it is known are 

 verumonfanum, caput gallinaginis, and colliculus seminalis. It is 

 about I inch long, and commences either a little below the urethral 

 orifice of the bladder or at the lower end of the uvula vesicae. As 

 it descends it gradually becomes more prominent, assuming a height 

 of about I inch, and then rapidly subsides. It is due to a thicken- 

 ing of the submucous tissue, which causes an elevation of the 

 mucous membrane. On account of this projection a transverse 

 section of this portion of the urethra is curved c«- crescentic, with 

 the convexity directed forwards. On either side of the crest there 

 is a longitudinal groove, called the prostatic sinus, into which the 

 majority of the prostatic ducts open. A few of these ducts, how- 

 ever, from the middle lobe open in the median line above the crest, 

 or, if the crest commences at the lower end of the uvula vesicae, 

 upon its upper part. Immediately below the most prominent part 

 of the crest there is the opening of a small blind recess, called 

 the utricle. The other names by which it is known are sinus 

 pocularis, vesicula prostatica, and uterus masculinus. Its direction 

 is upwards and backwards behind the middle lobe of the prostate, 

 and it is from J to ^ inch in length. It is somewhat flask-shaped, 

 being narrow at its urethral orifice, but expanded at its deep csecal 

 end. Upon the lateral margins of its orifice, or it may be just 

 within them, there are the minute openings of the common ejacula- 

 tory ducts. The utricle represents the uterus and vagina in the 

 female, being developed from the fusion of the posterior or caudal 

 ends of the Miillerian ducts. 



When the middle lobe of the prostate becomes hypertrophied, it 

 blocks the urethral orifice of the bladder, as has been stated, by 

 pressing the uvula vesicae over it from behind, and so gives rise 

 to difficulty in micturition, and obstructs catheterization. When 

 both lateral lobes become uniformly hypertrophied, the prostatic 

 portion of the urethra undergoes increase in length. When only 

 one lateral lobe is involved in the hypertrophy it presses against 

 the urethra, and, producing distortion of the canal, gives rise to 

 difficulty in micturition, and often considerable obstruction in 

 catheterization. 



Structure. — The mucous membrane of the prostatic urethra is 



