One of the most trying and difficult symptoms to interpret is pain. When the pain is not felt by the patient at the site of its origin but is referred to other and perhaps distant parts of the body, the difficulty obviously increases. Such pain is referred pain and is found in diaphragmatic pleurisy.
Capps,1 by means of a series of ingenious experiments on man, demonstrated, in 1911, that the visceral pleura is not endowed with pain sense and that the parietal pleura is richly supplied with sensory fibers from the intercostal nerves; that irritation of the parietal pleura produces pain that is accurately localized by the individual over the spot irritated. He demonstrated, at the same time, thatthe diaphragmatic pleura receives its nerve supply from two sources, the phrenic nerve and the lower six intercostal nerves. The intercostal nerves supply the peripheral rim of the diaphragm anteriorly and