THE URETERS 363 



placed (i) At its commencement; (2) opposite the transverse 

 process of the third lumbar vertebra ; (3) at the upper aperture 

 (brim) of the pelvis ; and (4) at its termination. The positions 

 of these constrictions and the relation of the ureter to the 

 transverse processes must be borne in mind in the examination 

 of radiograms, as, in this way, shadows thrown by impacted 

 calculi may be differentiated from shadows thrown by calcareous 

 lymph glands, etc. 



The ureter receives its blood-supply from the arteries to 

 which it is related as it descends from the kidney to the 

 bladder. They include the renal, spermatic, common iliac 

 and superior vesical arteries. The vessels conduct to the 

 ureter nerves of supply from the sympathetic nervous system, 

 and these nerves have their origin in the lower thoracic and 

 the upper lumbar regions of the spinal medulla. 



The ureter possesses a complete coat of unstriped muscle, 

 and it is believed that the passage of urine from the kidney to 

 the bladder is brought about by waves of peristalsis. The 

 presence of pus, a calculus or other foreign material in the 

 ureter produces excessive peristaltic contractions, which are 

 always associated with more or less acute pain. 



Ureteral Colic. The Pain in ureteral colic has a charac- 

 teristic distribution, which is of great help in diagnosis. When 

 the wave of contraction passes along the whole length of the 

 ureter, the pain commences on the dorso-lateral or dorsal 

 aspect of the trunk in the lumbar region. As the peristaltic 

 wave passes down, the pain passes round the trunk, but it 

 descends so as to reach a lower level in front than behind, and 

 it may finally radiate into the testis. 



Since the thoracic nerves supply strips of skin which are 

 almost horizontal (Fig. 69), it follows that the pain is not con- 

 fined to the distribution of a single nerve, but that it spreads 

 from the area supplied by one nerve to that supplied by the 

 nerve below. From examination of Figs. 60 and 61 it will be 

 seen that the pain in ureteral colic is experienced in the regions 

 supplied by the tenth, eleventh and twelfth thoracic and the 



