458 PHYSIOLOGY CHAP. 



Small branches of the renal artery pass from the pelvis to 

 the ureter, but other arterioles which come from the spermatic, 

 internal iliac, and inferior vesical arteries have an opposite course, 

 and run from ureter to pelvis. It is these branches that dilate 

 and develop after ligation of the renal artery, in order to re- 

 establish the renal circulation. 



Nerve fibres pass in the ureter from above downwards from the 

 renal plexus, and from below upwards from the hypogastric and 

 spermatic plexuses. Ganglion cells are scattered at irregular 

 intervals between these nerve fibres. 



The urine passes through the ureters less on account of gravity 

 than from the active peristaltic movements of their walls. On 

 exposing the ureter of an animal, or examining it in man, in cases 

 in which it has become accessible through laparotomy, it can be 

 seen that its contractions invariably begin at the extreme end of 

 the pelvis, and are peristaltically propagated towards the end near 

 the bladder. Antiperistaltic movements are normally never seen 

 in the ureters any more than in the intestine. It is natural to 

 suppose that the peristalsis of the ureters is excited by the urine 

 which trickles into them from the pelvis. In fact, after copious 

 draughts peristalsis is accelerated with the amount of urine 

 secreted. Urine, however, is certainly not a direct chemical and 

 mechanical stimulus, indispensable to the rhythmic movements of 

 the ureters, since the movements persist regularly even in ureters 

 cut out of the living animal with the kidneys, and sometimes even 

 in bits of isolated ureter. 



If the ureter be stimulated mechanically or electrically, at 

 any point, the same phenomenon appears that we noticed in the 

 heart, i.e. waves of contraction are produced in both directions, 

 one peristaltic, descending towards the bladder, the other anti- 

 peristaltic, ascending towards the pelvis (Engelniann, 1869). 

 These are automatic rhythmical movements, similar to those of 

 the heart, propagated solely by muscular paths, independent of 

 ganglion cells and nerve fibres. They have been observed by 

 Engelmann even in isolated pieces of ureter taken from the middle 

 of the duct, where no ganglion cells can be detected under the 

 microscope. 



The automatic rhythm of the ureters is sometimes regular (in 

 the rabbit three beats per minute can be counted), at other times 

 the movements occur irregularly, at others again they take the 

 form of groups separated by long pauses, which suggest the 

 periodic rhythm discovered by ourselves in the heart. 



In cases of atrophy of the human bladder, it is usually found 

 that the vesicular orifices of the two ureters do not open simultane- 

 ously, that their peristaltic movements do not follow at regular 

 intervals, that the amount of urine that flows from them in the 

 time unit varies considerably. It has also been stated that the 



