STRUCTURE OF THE URINARY BLADDER. 409 



(p. 412), to open into the urethral tube. Their length is rather length; 

 It- s> than an inch, and their course is convergent to their termination termination; 

 close to each other in the floor of the urethra. 



Structure. The wall of the common duct is thinner than that of structure, 

 the vesicula seminalis ; but it possesses similar coats. It is sur- 

 rounded by longitudinal involuntary muscular fibres, which blend 

 in the urethra with the submucous stratum. 



THE BLADDER. 



While the bladder is in the body, it is ovoidal in shape, and rather Form ; 

 flattened from above down (pp. 387 and 388) ; but out of the body it 

 is rounder than when in its natural position, and it loses the arched 

 form by which it adapts itself in distension to the curve of the pelvis. 



If this vise us is moderately dilated, it measures about five inches dimensions. 

 in length, and three inches across. Its capacity is greatly influenced 

 by the age and habits of the individual. Ordinarily the bladder 

 holds about a pint without inconvenience during life, though it can 

 contain much more when distended. 



STRUCTURE. A muscular and a mucous coat, with an intervening Coats of the 

 fibrous layer, exist in the wall of the bladder : at certain parts bladden 

 the peritoneum may be also enumerated as a constituent of the wall. 

 The vessels and nerves are large. 



The imperfect covering of peritoneum has been described (p. 378). Peritoneal. 



The muscular coat is formed of three thin layers of unstriated Muscular 

 muscular fibres, viz., an external or longitudinal, a middle or strata, 

 circular, and an internal or submucous. 



The longitudinal fibres (fig. 152, a ) form a continuous covering, External or 

 with the usual plexiform disposition of the muscular bundles, and J2? tudi " 

 extends from apex to base. Above, some are connected with the a ttach- 

 urachus and the subperitoneal fibrous tissue. Below, the posterior ments; 

 and lateral fibres enter the prostate ; while the anterior are attached 

 to the fascia covering the prostate, but a fasciculus on each side is 

 united to the back of the pubis through the anterior true ligament 

 of the bladder. On the front and back of the bladder the muscular 

 layer is stronger, and its fibres more vertical than on the sides, forms 

 Sometimes this outer layer of fibres is called detrusor urince from its JriJJ? * 

 action in the expulsion of the urine. 



The circular fibres (fig. 152, 2 ) are thin and scattered on the body Middle 

 of the bladder ; but around the cervix they are collected into a 

 thick bundle, the sphincter vesica, and are continuous below with the state, 

 fibres of the prostate. When these fibres are hypertrophied, they 

 project into the interior of the organ, forming the fasciculated 

 bladder ; and in some bodies the mucous coat may be forced out- 

 wards here and there between them, in the form of sacs, producing 

 the sacculated bladder. 



The submucous stratum (fig. 152, 3 ) forms a continuous layer over Submucous 

 the lower half of the bladder, but its fibres are scattered above. In la 

 the lower third of the viscus the fibres are longitudinal, and are ex 

 continued around the urethra ; but they become oblique above that 



