Since Mixter and Barr1in 1934 emphasized the significance of intraspinal protrusion of the intervertebral disks as an important cause of low back pain and sciatica, this condition has aroused no little interest. During the past few years considerable literature concerning the subject has appeared and the condition has been firmly established as a definite clinical and pathologic entity. Pathologic studies of a large series of protruded intervertebral disks by Deucher and Love2indicate that the protruded fragments are composed of fibrocartilage, portions of the nucleus pulposus and occasionally remnants of the notochord. These structures are not ordinarily opaque to roentgen rays and cannot be demonstrated per se in plain roentgenograms. Bone or calcium in quantities gross enough to be revealed roentgenographically is so rare in these protrusions that it is of little practical diagnostic importance. For this reason the roentgenologist is dependent on the use of some