Pathways for Pain From the Stomach of the Dog

For purposes of description the sensation of pain may be subdivided into two main categories: viz., somatic pain, produced by the noxious stimulation of the peripheral somatic nerves, and visceral pain, experienced after the appropriate stimulation of a viscus. In addition to these more common categories, a third variety of painful sensation, commonly designated as referred pain, is characterized by the fact that the painful sensation is interpreted by the subject as originating from the surface of the body, although it is known to be the result of the noxious stimulation of a viscus far removed from the painful area. It is generally agreed that stimulation of the parietal pleuroperitoneum by scratching or rubbing results in sensations of pain (Lennander 1 ; Alvarez 2 ; Morley 3 ), whereas stimulation of the visceral pleuroperitoneum is painless (Lennander 1 ; Capps and Coleman 4 ; Alvarez 2 ). Most authors have expressed the belief that the gastric