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
The Blood Book of "Immanuel's Veins", as it contains both new and different content than what was mentioned in "Immanuel's Veins", and is missing certain other details. A man whom Toma called Saint Thomas the Beast Hunter is implied to be the one who penned Toma's Blood Book. Ba'al's Blood Book was also mentioned briefly in Dekker's novel "Green", as it was compiled only about a year before "Green" took place. "The Blood Book" was first rumored by Dekker on his old forums sometime in 2008, before the release of "Green". There he spoke of a pair of journals, known as the "Blood