This fundamental space is entirely defined by the thinness of the tissue; the Anatomic generale enumerates twenty one: cells, the nervous tissue of animal life, the nervous tissue of organic life, arteries, veins, the tissue of the exhaling vessels, that of the absorbents, bones, medullary tissue, cartiles, fibrous tissue, fibro cartilaginous tissue, animal muscular tissue, muscles, mucous membrane, serous membrane, synovial membrane, glands, the derma, the epidermis, and hair.