Development of the Heart of a Chick
Heart of a chick at the 45th, 65th, and 85th hours of incubation. I, the venous trunks; 2, the auricle; 3, the ventricle; 4, the bulbus arteriosus.
Baker, W. Morrant & Harris, Vincent Dormer Kirkes' Hand-book of Physiology, 13th ed. (Philadelphia: P. Blakiston's Son & Co., 1892) 824