This illustration shows a representation of the circulation of the blood, in its essential features. The arrows indicate the course of the blood. a, arteries; aur., auricle or receiving portion of the heart; d, digestive tract; c. d., capillaries of the digestive tract; c.r., capillaries of the respiratory organs; c.s., capillaries of the system; va., valves; ve, veins; vt, ventricle.
Thomas Walton Galloway, Zoology A Text-Book For Secondary Schools, Normal Schools and Colleges (Philadelphia: P. Plakiston's Son & Co., 1913) 65
Courtesy the private collection of Roy Winkelman