The student is referred to the various publications of the Research Institute and Deason’s Physiology for experimental data confirming the validity of the osteopathic theory, although it should be emphasized that clinical evidence is quite conclusive. Malalignment injuries of the vertebral articulations, for example, ranging from imbalance of muscular tension to infections, is certain to result in some type of rotation and sidebending of the segments to an extent that apposition is compromised and abnormal anchorage supervenes. There are many factors of the pathology: muscular tension and fibrosis; damaged ligaments, particularly the capsular; interference of nervous stimuli, blockage of impulse directly and reflexly as shown by pathologic involvement in cord centers and sympathetic ganglia, and in certain cases direct obstruction of nerve fibers as revealed by Wallerian degeneration; involvement of circulation as shown by damage to blood-vessels, local edema and local acidosis, and effect upon local tissue respiration and drainage. Through a combination of these various factors circulation, nervous equilibrium and chemism of related parts are involved, both anatomical and physiologic balance is upset, and resistance of corresponding viscera affected. Reciprocal innervation and the axone reflex are also disturbed, all of which are important predisposing causes that disturb resistance of tissues and organs, upset their correlated mechanisms and render active various possible infections and toxins that otherwise a normal circulation, nervous and endocrine systems, and oxygen supply would rapidly and successfully combat and restore the organism to normal. Thus from the practitioner’s standpoint there are three points to always keep in mind: readjustment of the lesion; correction of the forces, habits, environment, etc. that produce the lesion; and hygienic attention of the body after lesion adjustment in order that normal condition may be maintained. A thorough study of the physiologic movements of the spine is a prerequisite to an understanding of the various possible abnormal appositions, though it should be appreciated that these movements are not consonant or applicable to many abnormal conditions. Pathology reveals many gradations and combinations not found in normal conditions. Frequently the key of a successful technique rests upon an understanding of the individual make up of the interosseous lesion.