For Hans Castorp understood that this living body, in the mysterious symmetry of its blood-nourished structure, penetrated throughout by nerves, veins, arteries, and capillaries; with its inner framework of bones⁠—marrow-filled tubular bones, blade-bones, vertebrae⁠—which with the addition of lime had developed out of the original gelatinous tissue and grown strong enough to support the body weight; with the capsules and well-oiled cavities, ligaments and cartilages of its joints, its more than two hundred muscles, its central organs that served for nutrition and respiration, for registering and transmitting stimuli, its protective membranes, serous cavities, its glands rich in secretions; with the system of vessels and fissures of its highly complicated interior surface, communicating through the body-openings with the outer world⁠—he understood that this ego was a living unit of a very high order, remote indeed from those very simple forms of life which breathed, took in nourishment, even thought, with the entire surface of their bodies.