Cartilage, or gristle, is a firm and very elastic substance occurring in vertebrate animals. When cut, the surface is uniform, and contains no visible cells, cavities, nor pores, but resembles the section of a piece of glue. It enters into the composition of parts whose functions require the combination of firmness with pliancy and flexibility, the preservation of a certain external form with the power of yielding to external force or pressure. The ends of bones entering into the formation of a joint are always coated with cartilage. Temporary cartilages are those from which bones are formed by ossification. The permanent cartilages are of various kinds. They are found in the external ear and aid in forming the nose, the larynx, etc. Research Cartilage