Giraffe have unusually high heart rates for their size, at 150 beats per minute. When the animal lowers its head the blood rushes down fairly unopposed and a rete mirabile in the upper neck, with its large cross sectional area, prevents excess blood flow to the brain. When it raises again, the blood vessels constrict and direct blood into the brain so the animal does not faint. The jugular veins contain several (most commonly seven) valves to prevent blood flowing back into the head from the inferior vena cava and right atrium while the head is lowered. Conversely, the blood vessels
Tales from the Heart with nine later issues published by Slave Labor Graphics (from 1988 to 1994). Slave Labor published "Tales from the Heart: Hearts of Africa" in 1994, which collected issues #1-3 and featured an introduction by Neil Gaiman. Two color graphic novels, "Tales from the Heart of Africa: The Temporary Natives" (1990) and "A Tale From the Heart of Africa: Bloodlines" (1992) were published by the Marvel Comics imprint Epic Comics. "A Tale From the Heart of Africa: Bloodlines" (Epic, 1992) was nominated for two Eisner Awards in 1993, for Best Single Issue, Self-Contained Story; and Best Graphic Album — New. Tales