364 THE GENITO-URINARY SYSTEM 



first lumbar nerves. The pain may also be felt in the proximal 

 part of the thigh (him bo-inguinal nerve, p. 165) and in the 

 buttock (iliac branches of T. 12 and ilio-hypogastric, etc.). 

 Further, the pain never affects the skin of the scrotum (S. 2, 3 

 and 4, p. 184), except in its proximal part (ilio-inguinal nerve, 

 L. i, p. 163). 



The testicular pain is explained (Mackenzie) by the fact 

 that the external spermatic nerve (genital branch of genito- 

 crural, L. i and 2) supplies a few sensory twigs to the tunica 

 vaginalis testis. 



The character, distribution and method of spread of the pain 

 in ureteral colic combine to support the view that the pain is 

 not experienced in the ureter itself. Ureteral colic, therefore, 

 may be regarded as an excellent example of the "viscero- 

 sensory reflex." 



At the same time it is very interesting to observe that cases 

 of ureteral colic often show a well-marked " viscero-motor 

 reflex" (p. 197). During the attack, the patient feels that the 

 testis is drawn up towards the abdomen and local examination 

 may reveal some boarding of the lower fibres of the internal 

 oblique and the transversus muscles. The upward movement 

 of the testis is produced by the cremaster muscle^ which covers 

 the testis and the spermatic cord. This muscle is really a part 

 of the internal oblique, and it receives its nerve- supply from 

 the external spermatic nerve (genital branch of genito-crural) 

 (L. 2). The lower parts of the internal oblique and the trans- 

 versus muscles are supplied by T. 10, n and 12, and L. i. 

 It is evident that the " overflow" (p. 191) of abnormal afferent 

 impulses from the ureter may stimulate the cells which are 

 concerned in the innervation of the internal oblique, transver- 

 sus and cremaster muscles. 



Attacks of ureteral colic, however, do not always begin in the 

 area of distribution of the tenth thoracic nerve. They may 

 commence either one or two segments lower down. If the 

 history of a case shows that attacks of pain, which originally 

 began at a higher level, have more recently begun at a lower 



