MUSCULAE MECHANISMS OF THE UEINAEY TRACT. 



BY ERNEST H. STARLING. 



CONTENTS : MOVEMENTS OF THE URETERS, p. 338 MOVEMENTS OF THE BLADDER, 

 p. 339 Muscular Tissue of Bladder and Urethra, p. 339 Mechanism of Closure 

 of Bladder, p. 340 Intravesical Tension, p. 341 Nerve Supply of the Bladder, 

 p. 342 Mechanism of Micturition, p. 344 Voluntary Control of Micturition, 

 p. 345. 



MOVEMENTS OF THE URETERS. 



THE urine, which is secreted continuously, though at varying rates, 

 passes to the bladder through the ureters, partly in consequence of 

 the pressure at which it is secreted, partly in consequence of peristaltic 

 contractions of these tubes. 



These contractions begin at the upper end of the ureters, and travel 

 down to the bladder, but do not affect the musculature of the latter. 

 Although, by artificial stimulation, contraction waves may be started at 

 any point in the ureter, from which they will then travel upwards as 

 well as downwards, under normal conditions the contractions always 

 take place from above downwards, no spontaneous antiperistaltic waves 

 having ever been observed. The contraction waves, according to Engel- 

 mann, 1 travel at about 20 to 30 mm. in the second, and are repeated at 

 the rate of about three in the minute. 



If the ureter is divided about its middle, the upper half still 

 continues to present rhythmic waves of peristalsis. The lower half often 

 begins to contract on its own account, but its rhythm now no longer 

 coincides with that of the upper half. 



The contractions seem to be initiated by the muscular tissue of the 

 walls of the ureter. Although (in man) the ureter receives fibres from 

 the mesenteric, spermatic, and hypogastric plexuses, and contains a few 

 ganglion cells, the middle third of the ureter is, according to Engelmann, 

 free from nervous elements, and yet contracts rhythmically when 

 isolated from the other segments. According to Dogiel, 2 Maier, 3 and 

 Protopopow, 4 however, ganglion cells may be found in all parts of the 

 ureter, although more abundant at the two ends. The contractions 

 are altered to a certain extent by distension of the ureter, yet they are 

 largely independent of the urinary flow, and occur almost as frequently 

 in animals which have been deprived of water, as when the urinary flow 

 is excessive in consequence of administration of large amounts of fluid. 



Contractions of the ureter can be excited by stimulation of the 



1 Arch.f. d. ges. PhysioL, Bonn, 1869, Bd. ii. 



2 Arch. f. mikr. Anat., Bonn, Bd. xv. S. 64. 



3 Virchoufs Archiv, 1881, Bd. Ixxxii. S. 49. 



4 Arch.f. d. ges. PhysioL, Bonn, 1897, Bd. Ixvi. S. 1. 



