Page:Structure and functions of the body; a hand-book of anatomy and physiology for nurses and others desiring a practical knowledge of the subject (IA structurefunctio00fiskrich).pdf/107

 CHAPTER VIII.

THE HEART AND CIRCULATION.

—The heart. (Stoney.)

The Heart.—Shielded within the chest are, as has been said, the heart and lungs. The heart lies on the left side behind the sternum and the cartilages of the fourth to seventh ribs in a closed, conical, membranous sac, the pericardium, which is attached by its base to the central tendon of the diaphragm, and whose point extends up between the pleuræ of the lungs. This sac has an external fibrous layer and an internal serous layer that is reflected back over the heart itself, forming a closed sac,