The Palmer School of Chiropractic is one of the first schools of chiropractic and is today the largest. Founded by the founder of chiropractic, the school teaches a system of spinal adjustment called the H.I.O. ("hole in one")," whereby the atlas (the first vertebra at the top of the spine) is adjusted in different directions, depending upon measurements made on an X-ray film. (The neologism "Hole-In-One" was originally coined to imply that a perfect adjustment in the upper cervical region of the neck would cause everything else to "fall into place.").
The founder, B.J. Palmer, stated that only the atlas could cause misalignment below the point, therefore putting pressure on the spinal cord or spinal nerves and causing disease.