EXAMINATION OF THE PREPUCE AND URETHRA. 153 



the diameter of the urethra is less and the part at that portion has slight 

 contractile properties. By a gradual pressure the stricture is overcome 

 and the catheter passes upward to the arch of the perineum ; here the 



Fig. 43. 



Passing the catheter. 



wire-stylet must be withdrawn from the catheter at least one-third, so as 

 to allow the catheter to make the curve ; a gradual pressure soon brings it 

 into the bladder, when the wire can be removed entirely. 



Fir. 44. 



Median section through the pelvic cavity ; a, rectum ; 6, vagina ; V, vulva ; d, bladder ; 

 e, urethra ; I, pubic symphysis. 



In the bitch we generally use a metallic catheter, either silver or Ger- 

 man silver (Fig. 42, B). The instrument is passed up on the floor of the 

 vagina until it comes in contact with the urethral opening (see Fig. 44) ; 

 this is closed with a slight sphincter (the so-called urethral valve) ; this is 



