PRACTICAL CONSIDERATIONS : MALE URETHRA. 1929 



The prepubic curve can be straightened by erecting or raising up the penis as 

 is done during the use of urethral instruments, most of which, especially sounds and 

 catheters, are made so as to correspond in their curves to the theoretical fixed curve 

 above described. The catheters employed in certain conditions, especially prostatic 

 hypertrophy, are elongated and given a larger curve to correspond with the elonga- 

 tion of the prostatic urethra and the greater curve given it by the elevation of the 

 vesical neck (page 1981). 



(dT) As the urethra, when not distended by the passage of urine, semen, or 

 instruments, is a mere valvular slit, the walls lying in contact, it has to be studied as 

 to width or narrowness by various methods of dilatation during life and of injection 

 upon the cadaver. The result of such studies demonstrates that the narrow and 

 wider portions of the urethra alternate as follows : the external meatus (the nar- 

 rowest), the fossa navicularis, the spongy urethra, the bulbous portion, the mem- 

 branous urethra, the prostatic urethra, the vesical orifice. 



(e) As to its dilatability , i.e. , its susceptibility to distention by instruments, 

 the meatus is the least distensible, and then, in order, follow the membranous, 

 spongy, bulbous, and prostatic portions, the latter being the most distensible. 



A definite ratio (nine to four) has been thought to exist (Otis) between the cir- 

 cumference of the flaccid penis and that of the distended urethra. A certain propor- 

 tionate relationship in size between the calibre of the urethra and the circumference of 

 the penis does undoubtedly exist, but neither is it so definite nor is the urethral cali- 

 bre so large as the above figures would indicate. 



(/") At the point at which the prostatic urethra enters the bladder it is sur- 

 rounded by the internal vesical sphincter, a muscle made up of unstriped fibres ; anterior 

 to this a double layer of unstriped muscular fibres and the glandular structure of the 

 prostate surround the urethra. At the apex of the prostate lies the external vesical 

 sphincter, made up chiefly of voluntary muscular fibres. 



The discharge of urine from the bladder is prevented by the tonic contraction of 

 the muscular apparatus of the membranous and prostatic urethra. As the bladder 

 becomes distended, the internal vesical sphincter yields and the urine enters the pos- 

 terior part of the prostatic urethra, causing a desire to urinate, which is resisted by the 

 action of the voluntary fibres of the external vesical sphincter and the compressor 

 urethrse. On passing a catheter when the bladder is full, the urethra seems about an 

 inch shorter than it does immediately after micturition ; this is owing to the participa- 

 tion of the posterior portion of the prostatic urethra in the retentive function of the 

 bladder. 



The compressor urethrse muscle is readily excited to reflex spasm. Ordinarily, 

 on the passage of instruments, a moderate degree of resistance can be detected, due 

 to the contraction of this muscle. In irritable conditions of the mucous membrane 

 there may be excited a spasm so violent that it will be impossible to introduce a soft 

 instrument. Such spasm may also be excited by irritation of the prostatic urethra 

 either from distention of the bladder or from any other cause. Thus it is often found 

 extremely difficult to evacuate the bladder when the desire to urinate has been re- 

 sisted for many hours, and acute inflammation of the posterior urethra not infrequently 

 requires the use of catheters to overcome the tight muscular contraction of the com- 

 pressor urethrae which prevents micturition. Not only the introduction of sounds, but 

 even the injection of bland liquids will cause contraction of the compressor urethrae 

 muscle, and hence prevent such injection from reaching the membranous or the pros- 

 tatic urethra. Any inflammation in these portions of the urethra will also cause the 

 tonic contraction of the sphincter muscles to be accentuated. Hence inflammatory 

 discharge from the membranous or the prostatic urethra will tend to flow, not for- 

 ward, but into the bladder, and injections intended to reach the deep urethra will, if 

 driven in at the meatus, extend no farther back than the inferior layer of the trian- 

 gular ligament. 



There seem, then, to be good grounds, both from a physiological and from a 

 clinical stand-point, for dividing the urethra into an anterior erectile part and a pos- 

 terior muscular part. 



() The penile urethra terminates at the anterior margin of the suspensory liga- 

 ment ; the perineal urethra includes the bulbous (with the so-called pretrigonal or 



