Abdominal Pain

IT has loig beeni known that the abdominal viscera are insensitive to cutting, bUrning, anld other forms of trauma that indluce pain when1i applied to the somatic tissues, i.e., skin, muscle, etc. 'rhis fact led nmanx' clinicianis to the belief that true visceral pain does Inot exist, andl that the paini presenit in certaini forms of visceral disease is caused either by inflammatory or other pathological involvement of the peritoneum. This involvement, it is said, may maniifest itself either as a painful impression at the site of the lesion, or be referred to some distant area of skini or muscle. For example: An inflammatory reaction inlvolvinig the peritoneum covering the uin(ler aspect of the diaplhragmii max manifest itself by an area of paini, which may or mav not be accompaniedl by hyperesthesia, over the shoulder of the same side. 'T'he (liagram shown in fig. 1 is an illustration of the path whereby the painful impulses may pass. 'I'he stimulus is received in the sub-phreniic plexus P, travels along the phrenic nerve A to the spinal ganiglion 13, and(i thence to the spinal cord, whlere it forms what Szemiiol calls a "focus of irritatioln" at the synapse C, at the level of the fourth cervical nerve-segnment. The upper neuroni D, coninecting with both A and G (the periphleral nierve to the shoul(ler), crosses to the opposite side in the lemniscus, ascends to the thalanlius E, an(d finally reaches the cortex of the brain F. Ihen, since the neuron A has never beeni educatedl to feel or localize pain directly, the cortex registers the paini along the (lominanit and(i usual pathway of neuron G, comiling from the area markeld vith shaded lines over the slhoul(ler. Doubt, however, has been cast on the view%x that the peritoneum is thc only source of abdominal pain, and many observers nowr believe that certain forms of pain can be appreciated by the viscera themselves. Recently Livingstone2 carried out a series of experimenits in a case of sigmoid colostomy, which supports this view. His description of thcse experiments is as follows:"My patient was a co-operative and intelligent woman well qualified to analyze her sensations. I was unable to elicit the slightest pain or any form of sensation by stimulating the gut by a great variety of chemical and mechanical meanis. When the gut was stronglystimulated with the in(luctorium there followedla rapid blanclling of the tissues, and(l subsequently a peristaltic conitractioni made itself evident. She experienced no sensation upoIn conitractinig the electro(le to the gut, nor at the time of the blanching, but stated that she experienced cramp-like pain across the lower abdomen at the time the contraction was markedl. She described the senlsationl as a 'gas-pain,' and was confident that it seemed to be within the ab(lomen and not in the parietes. TIhe paini subsi(led gradually a few seconds after the removal of the electr-ode, often before the blanichinig had disappeared. She also experienice(l (liscomfort when a small rubber balloon within either loop of the