Radiology of the diaphragm as two muscles

In order to investigate the postulate that the diaphragm consists of two muscles, cineradiographic studies and plain roentgenograms were taken of the diaphragmatic movement in eight dogs. A characteristic pattern of contraction was seen following direct electric stimulation of each of the sections of the diaphragm, namely the costal muscle, mainly anterior to the central tendon, and the smaller, posterior crural muscle. Stimulation of the roots of the phrenic nerves in the neck showed that, with C5 root stimulation, contraction of the costal area occurred, but that with C6 and C7 root stimulation, contraction of the crural area occurred, although the movement was larger with C6 than with C7 root stimulation. Downward displacement of the entire diaphragm followed stimulation of the intrathoracic phrenic nerves. These results support the concept that the canine diaphragm actually consists of two muscles with a different segmental innervation of each part.