_Pulsion diverticulum of the esophagus_ is an acquired hernia of the mucosa between the circular and oblique fibers of the inferior constrictor muscle of the pharynx. A congenital anatomic basic factor in etiology probably exists. The pouching develops in the middle part of the posterior wall, between the orbicular and oblique fibers of the cricopharyngeus muscle, at which point there is a gap, leaving the mucosa supported only by a not very resistant fascia (Fig. 100). When small, the sac is in the midline, but with increase in size, it presents either to the right or the left side, commonly the latter. The sac may be very small, or it may be sufficiently large to hold a pint or more, and to cause the neck to bulge when filled. When large, the pouch extends into the mediastinum. It will be seen that anatomically the pulsion diverticulum has its origin in the pharynx; the symptoms, however, are referable to the esophagus and the subdiverticular esophagus is stenosed by compression of the pouch; therefore, it is properly classified as an esophageal disease. [FIG. 100.--Schema illustrative of the etiology of pressure diverticula. O, oblique fibers of the cricopharyngeus attached to the thyroid cartilage, T. The fundiform fibers, F, encircle the mouth of the esophagus. Between the two sets of fibers is a gap in the support of the esophageal wall, through which the wall herniates owing to the pressure of food propelled by the oblique fibers, O, advance of the bolus being resisted by spasmodic contraction of the orbicular fibers, F.] _Etiology_.--Pressure diverticula occur after middle life, and more often in men than in women. The hasty swallowing of unmasticated food, too large a bolus, defective or artificial teeth, flaccidity of tissues, and spasm of the cricopharyngeus muscle, are etiologic factors. Cicatricial stenosis below the level of the inferior constrictor is a contributory cause in some cases.