THE BLADDER 367 



The peritoneum covers the whole of the superior surface of 

 the bladder, but it does not clothe the posterior (Fig. 127) or 

 the infero-lateral surfaces. Anteriorly, it is reflected from the 

 apex of the bladder on to the anterior abdominal wall, and 

 laterally it passes from the upper surface on to the side walls of 

 the pelvis. Posteriorly, the peritoneum touches the fundus 

 of the seminal vesicle (Fig. 127) and passes backwards to the 

 anterior surface of the rectum. 



When the bladder fills, it rises up out of the pelvis into the 

 abdomen, since it is unable to thrust the prostate downwards 

 owing to the presence of the urogenital diaphragm (p. 379), 

 which fills up the pubic arch. As the viscus distends, the 

 superior and the infero-lateral surfaces become increased in 

 size, but the posterior surface is not much altered. The peri- 

 toneum which covers the superior surface of the empty bladder 

 cannot stretch sufficiently to enable it to cover the whole 

 surface when the viscus is enlarged. As a result, the bladder 

 strips the peritoneum off the anterior abdominal wall and the 

 side walls of the pelvis. In this way, the anterior part of the 

 inferior aspect of the bladder is brought into contact with 

 the lower part of the transversalis fascia, and no peritoneum 

 intervenes between the two structures (Fig. 128). In cases, 

 therefore, in which the surgeon is unable to draw off the urine 

 from a distended bladder per 'uretAram, the bladder may be 

 punctured supra-pubically without fear of infecting the peri- 

 toneal cavity. In some cases, however, leakage occurs into 

 the retropubic space (of Retzius). 



The mucous membrane of the bladder is redundant and is 

 thrown into folds when the viscus is empty. The underlying 

 submucous tissue is very loosely arranged and, therefore, the 

 muscular and mucous coats are not firmly adherent to one 

 another. On account of this arrangement, it is possible for 

 the bladder to become distended without any undue stretching 

 of the mucous membrane. 



It has already been pointed out that the posterior sur- 

 face of the bladder undergoes but little alteration, while the 



