20ac M edium, not matter, postulated in the 19th century to permeate all space and tranmit electromagnetic waves such as light. (5) (E?j?r) 36ac Fourth or true compartment of a ruminant mammal`s stomach, connected to the small intestine. (8) (A?o??s?m) 25d Joint in the lower leg of a horse or related animal between the cannon bone and the pastern.(7) (F??c?c?)