The regulation of the heart beat.

"Ernest Henry Starling (1866-1927) has probably contributed more than any man to our understanding of heart failure....His work with Patterson and Piper on the mechanical factors involved in the response of the heart to changes in load have formed the basis for our understanding of how the heart's work as a pump is adjusted to the varying demands made upon it, and have incidentally provided the key to our understanding of heart failure as seen in man" ( Sir George Pickering, "Starling and the concept of heart failure," Circulation, 21 (1960) 323-331).