Sclera nitrogenous sugar, hexosamine) to embed the fibrils. The cornea, unlike the sclera, has five layers. The middle, thickest layer is also called the stroma. The sclera, like the cornea, contains a basal endothelium, above which there is the lamina fusca, containing a high count of pigment cells. Sometimes, very small gray-blue spots can appear on the sclera, a harmless condition called scleral melanocytosis. Human eyes are somewhat distinctive in the animal kingdom in that the sclera is very plainly visible whenever the eye is open. This is not just due to the white colour of the human sclera, which many
The Description of the Human Body He believed the heat of the heart somehow caused all movement of the body. Blood vessels he realized were pipes, he saw that veins carried digested food to the heart. (This was brought further by William Harvey. Harvey developed the idea of the circulation of the blood.) Descartes felt that an energetic part of blood went to the brain and there gave the brain a special type of air imbued with vital force that enabled the brain to experience, think and imagine. This special air then went through the nerves to the muscles enabling them to move. The Description of