rare = "myelination". Compare "medulla".
The presence or development of a medulla in a stele; the condition of having such a medulla.
3The presence of a medulla in a hair or feather; the nature or size of the medulla in hairs; the condition of having medullated hairs; the degree to which the hairs (of an animal, type of wool, etc.) are medullated.
Late 19th century; earliest use found in Philosophical Transactions of the Royal Society of London. From medulla + -ation.