474 



URO-GEN1TAL SYSTEM. 



consequently have slow and lazy contractions; but they nro, 

 moreover, very elastic, and allow the bladder to dilate readily, 

 as well as the urine to accumulate in large quantity. When 

 this dilatation is pushed to its extreme extent, it becomes a 

 cause of irritation to the muscular fibre, which will then con- 

 tract, and the bladder expel its contents. We shall soon see 

 that this reaction occasions a desire to urinate. When there 

 is inflammation of the bladder, its muscular walls are less 

 elastic (see. Physiology of the Muscle), and these more 

 quickly react upon the contents of the reservoir, and occasion 

 in such cases frequent desire for micturition. 



The important question now presents itself as to how the 

 urine, during the quiescence of the bladder, is retained in 

 this reservoir and does not escape through the orifice in the 

 neck of the bladder. We all know that this is closed by a 

 contraction of the vesical sphincter which surrounds the 

 opening ; but these muscular fibres are not very pronounced, 

 nor can a muscle be kept in a continual state of contraction. 

 The neck of the bladder is closed, because this is its natural 

 form, like that of other and similar circular muscles ; these 

 obliterate the orifice which they circumscribe, when they are 

 in a state of repose, and this is simply due to their elasticity. 

 But so soon as some cause opposes 

 this sphincter, it becomes powerless 

 to prevent the passage, which the 

 urine overcomes and rushes through. 

 With women this orifice is differ- 

 ently arranged, and on a slight effort, 

 or burst of laughter, several drops 

 of urine may gush out. Certain 

 arrangements and especial positions 

 of the bladder, especially in man, 

 are of such a nature that there ex- 

 ists no real orifice while the bladder 

 is in a state of repose, 

 organs First, the axis of the bladder 

 (Fig. 129) is by no means vertical, 

 but almost horizontal (this organ rests upon the symphysis 

 pubis, which has almost a horizontal position) ; the excretory 



* S, Symphisis pubis. pi, Plexus of Santorini. V, Bladder. 0, Remains 

 of the urachus. Pj>, Prostrate gland. U/>, Prostatic utricle. Cd, Deferent 

 canal. Vs, Vesiculte seminales, whose neck joins with the deferent canal to form 

 the excretory duct, which may be seen going behind the prostatic utricle. 

 W, The so-called Wilson's muscle (pubo-urethral band). Gp, Cowper's gland. 

 1), Bulb of the irethra. 



Cct 



Fig. 129. -Bladder and 



of micturition.* 



