Diaphragmatic Hernia is perhaps the commonest. There is a congenital form in which a sac is protruded through one of the normal apertures, or through a part of the diaphragm which by reason of defective development has given way. The protrusion is into the chest, and the sac may contain intestine, spleen, liver, stomach. There is also an acquired form, due nearly always to some injury to the diaphragm, and the hernia is frequently devoid of a proper peritoneal sac.

From a case recorded by Dr. Adams, it appears that a tumour growing against the diaphragm (in his case from the capsule of the spleen) may so weaken it as to lead to hernial protrusion. In diaphragmatic hernias from rupture, a large portion of the abdominal viscera may be protruded.