THREE FIGURES
Reference has been made t o the blood supply to the atrioventricular node of the dog by many authors (Moore, '30; Pianetto, '39 ; Gloniset and Glomset, '40 ; Nonidez, '43; Baird and Robb, '50; Copenhaver and Truex, '52). Several of these observations were made in passing, since the blood supply to the atriovcntricular node was not the chief interest of the particular author a t that time. Despite the several allusions to the arteries supplying the node, there is little agreement as to the source of these vessels and how they are disposed within the node.
Since the dog is one of the common laboratory animals used in cardiovascular research, the blood supply to its atrioventricular node should be of interest. A better understanding of this problem might aid in the interpretation and explanation of some of the rhythmic disturbances in the heartbeat seen during experimental procedures. The aim of the present investigation is to indicate the source of the arteries to the interatrial septum and to the atrioventricular node of the dog and their disposition within the node.
MATERIAL AND METHODS
Sixty-five dog hearts were utilized in this investigation. Most of the animals were obtained from student laboratories