THE PHYSIOLOGY OF MICTURITION 1291 



until its orifice has actually entered the bladder. The wall of the 

 urethra is surrounded by circular muscular fibres, which, by their 



Ant. long. m 

 Circular muse 



Pubo-vesical m. 

 Symphysis 



Ant. circular m. 

 Ant. long. m. 



Os pubis 

 Sphincter urogenitalis 



Circular 

 Longitudinal 



Os pubis 



Circular coat 

 Longitudinal coat 

 Sphincter trigoni 



Prostate 



Circular coat 

 Longitudinal coat 



Sphincter trigoni 



Circular coat 

 Longitudinal coat 



Sphincter trigoni 

 Longitudinal muscle 



Fibres running to urethro- 

 vaginal septum 



FIG. 536. Sagittal sections through neck of bladder. 



(METZNER after KALISCHER.) 



A, in middle line (male) ; B, slightly to left of middle line (male) ; 

 c, ditto (female). 



tonic contraction, will also tend to prevent the escape of urine along 

 the canal. This urethral muscle is strengthened by two sphincter 

 muscles which are voluntary and composed of striated fibres. The 

 chief one, which has been named by Kalischer the sphincter urogenitalis, 



