Cutaneous pain may be the expression of a pathologic process in the posterior nerve roots. The process is manifested at the periphery in the region that contains the sensory receptors for the involved roots. The referred pain of visceral origin may also be perceived in the external surfaces that contain sensory receptors of spinal roots. The latter pain is the expression of an abnormal stimulation of a viscus through a reflex arc that includes the posterior nerve roots.1It is obvious, therefore, that the pain of root-zone distribution associated with hypertrophic ostearthritis of the spine2might readily be confused with the pain of abnormal visceral stimulation that is perceived within the same dermatomes. That the differentiation of pain over the precordium3is not always easy was remarked by Mackenzie,4who pointed out that the pain in the viscerosensory reflex associated with organic disease of the heart