pushed into the arteries when the heart contracts; meanwhile, excess air in the lungs has
absorbed or “sucked up” some of the superfluous heat of the body and the heart, and is
exhaled when the thorax contracts. Following the basic principle (“an empty space fills up”),
new breath (pneuma) rushes into the expanding thorax. Thus Erasistratos explained how
the breathing-cycle both cools the body and provides the arteries with essential pneuma
(Scarborough 1998: 175) To explain why the arteries are empty but the veins are full of
blood, Erasistratos argued that when an artery is severed, it spurts blood because there are
(theoretical) extremely minute blood vessels, the sunastomo ̄seis (invisible to the eye), that con-
nect blood-filled veins to arteries (Gale ̄n, Blood in the Arteries 2 [4.709 K.] = Furley and Wilkie
150 = Garofalo, fr.109 [parempto ̄sis]), and therefore blood rushed into the severed artery.
Erasistratos’ theory led to the capillaries, not demonstrated until the 17th c. by Malpighi in
De pulmonibus observationes anatomicae (1661): using a microscope was the key (Major 1954:
1,511). Erasistratos’ postulation of sunastomo ̄seis allowed his system to “work,” and his dissec-
tions gave a physiology founded on anatomy. Telling is the absence of blood in a “normal”
artery (which Gale ̄n condemned in Venesection against Erasistratos, and proved wrong in Blood
in the Arteries): no observed arterial blood (esp. in the aorta) in the living human, thus no
vivisection of humans (Scarborough 1976).
Works known by title and shorter and longer quotations in A A, the
L , C, D, Gale ̄n, M, O,
R E, S, and others (see Garofalo, “Index Fontium” and “Index
auctorum et locorum”) are Fevers (frr. 194 – 226 Garofalo), Expectoration of Blood, Paralysis,
Dropsy, Podagra (viz. Gout [frr. 267 – 269]), The Abdominal Cavity, and Divisions. In the last,
Erasistratos enunciated the famous dictum that “every organ is supplied by an artery, a
vein, and a nerve,” and he confirmed He ̄rophilos’ observations of the “two parts” of the
brain, re-emphasizing that human cranial convolutions were far more complex than those
in animals, which proved higher human intelligence (geometry easily demonstrated a
“greater surface area”). Erasistratos rejected the Hippokratic notions of a humoral path-
ology, teaching that blood in the veins and two kinds of pneumata were essential for life.
Detailed dissection of the heart yielded description of the semi-lunar valves and the tri-
cuspid valve, which he named and understood prevented reflux of blood. The list of
accurate descriptions (many from Abdominal Cavity [frr. 258 – 269 Garofalo]) is impressive: the
aorta, the pulmonary artery, the intercostal arteries, hepatic artery, the arteries of the
stomach, pulmonary vein, vena cava, the azygos vein, the milk-white vessels of the mes-
entery (lymphatic vessels [Gray, Anatomy, 800–803]), and the complicated courses of the
hepatic veins.
The function of the nerves also followed the same basic principles. The nerves also
carried “vital” (zo ̄tikon) pneuma, “pushed” through the arteries from the left ventricle of
the heart to the brain, where the pneuma gains further refinement into a “psychic” (psu-
khikon) pneuma, lacking any notion of “soul”; this then is “pulled” throughout the body by
means of the two kinds of nerves (we call them “sensory” and “motor”). Sight requires the
most “psychic” pneuma, and thus the optic nerve has the greatest “psychic” pneuma, and
was tubular or hollow for the pneuma directed at the eye. Meanwhile, appetite and diges-
tion gave the liver liquid nourishment so that it could “process” food into blood, then
“pushed” into the veins by his principle “all empty spaces are filled up.” Arteries + nerves,
therefore, contain only pneuma, and the veins have blood, “pushed” as nutriment to all
parts of the body. Also, therefore, all parts, muscles, and organs, to live and grow must have
“triple-woven” (triplokiai) ingrowths of veins, arteries, and nerves; pneuma “pushed” to
ERASISTRATOS OF IOULIS ON KEO ̄S