The impulse of the right ventricle, F, has been noticed occasionally as corresponding to a point somewhat above the middle of the sternum and the intercostal space between the fourth and fifth left costal cartilages; while in other instances its beating was observable as low down as an inch or more below the Xiphoid cartilage, and these variations have existed in a state of health.
"Surgical Anatomy"
Joseph Maclise
The posterior extremity of the sternum, flattened from above downwards, ends in a cartilaginous plate; concave superiorly, and convex inferiorly: this is the abdominal prolongation, or Xiphoid appendix.
"Artistic Anatomy of Animals"
Édouard Cuyer