PELVIS MINOR 467 



consequently there are two on the left side and one, the 

 largest, on the right side. Each is formed by an infolding 

 of the mucous, submucous, and part of the muscular coat. 

 The positions of the folds are variable; but the right and 

 largest is usually placed at the level of the bottom of the 

 recto -vesical excavation of peritoneum, whilst the two folds 

 of the left side are situated, one 38 mm. (an inch and a 

 half) above the right fold, and the other the same distance 

 below it (Birmingham). 



The Structure of the Walls of the Bladder. The bladder 

 possesses the following five coats : 



i. Serous. 2. Subserous. 3. Muscular. 4. Submucous. 5. Mucous. 



The serous or peritoneal covering has already been examined. 

 The subserous coat is a thin stratum of areolar tissue which 

 connects the peritoneum with the muscular coat. 



The Muscular Coat. The fibres of the muscular wall of 

 the bladder are arranged in three layers : 



i. External longitudinal fibres. 2. Circular fibres. 3. Internal longi- 

 tudinal fibres. 



The external longitudinal fibres, frequently spoken of as 

 the detrusor urincz, spring from the back of the pubic bones, 

 the pubo-prostatic ligaments, and the base of the prostate. 

 They ascend from those attachments over the anterior border 

 and the medial parts of the infero- lateral surfaces of the 

 bladder. At the apex a few pass into the urachus, but 

 the majority pass backwards over the superior surface and 

 the base of the bladder to the prostate, to which they are 

 attached. On the lateral parts of the infero-lateral surfaces 

 and on the lateral borders of the bladder, the longitudinal 

 layer is less complete, and the fibres take a more oblique 

 direction. 



The circular fibres are arranged in coarse bundles which 

 run obliquely as well as circularly round the bladder, and 

 constitute the greater part of its muscular coat. At the 

 internal urethral orifice the bundles become finer and are 

 massed together to form a sphincter, the fibres of which are 

 more or less continuous with those of the prostate. 



The internal longitudinal fibres are absent on the fundus, 

 and form only an incomplete layer on the other walls of the 

 bladder. 



The Submucous Coat. The submucous coat is a layer 



H30 a 



