As disease of the coronary arteries plays such a dominant role in cutting short the productive age of man, it has long been the subject of study. The clinical observations of Morgagni, Rougnon, Heberden and Parry long preceded experimental studies on animals. During the middle of the nineteenth century several investigators, among whom were Erichsen,1 Panum,2 von Bezold and Breymann3 and Samuelson,4 observed the effects of ligation or embolism of the coronary arteries. The discussions were mostly concerned with the manner of the cardiac standstill, and the experiments were not designed for study of the collateral circulation in the heart. The greatest controversy arose over a manufactured term, "functional end artery," which was introduced by Cohnheim and von Schulthess-Rechberg5 in 1881. In the main, the difficulty arose between the anatomists, who could so clearly see the collateral vessels, and the experimental pathologists, who observed necrosisof the myocardium following ligation