medulla
me.dul.la \m*-'d*l-*\ \-'d*l-(.)e-, -.i-\ n or medullas or me.dul.lae [L] pl pl medullae 1: MARROW 2a: the inner or deep part of an animal or plant structure 2b: MEDULLARY SHEATH
Webster's English Dictionaryme.dul.la \m*-'d*l-*\ \-'d*l-(.)e-, -.i-\ n or medullas or me.dul.lae [L] pl pl medullae 1: MARROW 2a: the inner or deep part of an animal or plant structure 2b: MEDULLARY SHEATH