MICTURITION 391 



A. THE URETERS 



Contractions of the ureters begin always at the upper end and pass pro- 

 gressively downward to the bladder, but do not involve the musculature of 

 the latter. They appear to be started by the entrance of the urine into the 

 ureters themselves. After one contraction the lumen gradually fills again at 

 its upper end, until the next one follows. 



In the ureters of man subjected to direct observation it has been found that 

 as a rule the bladder ends of the two do not contract at the same time, that in 

 the same ureter the contractions do not succeed each other at regular intervals, 

 and that the total quantity of urine conveyed in a unit of time varies greatly. 

 The maximum quantity delivered to the bladder by a single contraction is placed 

 at 4 c.c. On the contrary, Bardier and Frankel have found that the flow of urine 

 from the ureters of dogs is generally pretty uniform whether one or both be 

 considered. 



Fagge states that stimulation of the hypogastric nerve produces a series of 

 contractions of the ureter. Furthermore, the ureter when entirely cut out of 

 the body contracts rhythmically. Whether these contractions are due to ganglion 

 cells present in the wall of the ureter, concerning whose occurrence authors still 

 differ, or whether they are due essentially to the automatic activity of the mus- 

 culature of the wall (Engelmann), is not yet decided. 



B. THE URINARY BLADDER 



The ureters pierce the bladder wall obliquely. The greater the pressure inside 

 the bladder becomes, the more securely are the mouths of the ureters closed ; the 

 consequence of which is that the return of urine from the bladder to the ureters 

 is prevented. However, this closure is not absolutely secure; for although no 

 return flow is possible so long as the bladder wall is passively stretched, it may 

 happen when the wall contracts, as it will, for the purpose of preventing excess- 

 ive distention. Entrance to the ureter is possible even then only at the end of 

 a contraction of the ureter itself, when its mouth is open. In the dog, each 

 mouth is guarded by a strong muscular band. If this band be cut, regurgitation 

 is comparatively easy. From the ureter the urine may pass on into the pelvis 

 of the kidney and be pressed into the lymphatics and the renal tubules, thence 

 in some way or other into the renal vessels. Even solid matters from the urinary 

 bladder can in some such way reach the general circulation (L. Lewin). 



The closure of the external opening of the bladder appears to be accom- 

 plished mainly by its anatomical position, for after death when the voluntary 

 sphincters are relaxed, the urine does not escape. However, the bladder will 

 stand a stronger internal pressure, without being emptied, during life than 

 it will after death. The difference is due to the external sphincter and the 

 so-called internal sphincter i. e., the strong band of muscle fibers beginning 

 on the neck of the bladder and reaching to the prostate (Eehfisch). 



The desire to urinate is in all likelihood roused primarily by the sense 

 of fullness of the bladder. This is preceded by a greater degree of ten- 

 sion of the bladder wall. Cold and warm fluids in the bladder also cause 

 the sensation named and the consequent desire to urinate, but indifferent 

 fluids at the temperature of the body, especially urine, are not felt at all. 

 Stimulation of the prostatic part of the urethra is felt, but does not pro- 



