| medullary sheath | |
| —n | |
| 1. | anatomy a myelin layer surrounding and insulating certain nerve fibres |
| 2. | a layer of thick-walled cells surrounding the pith of the stems of some higher plants |
| an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle. |
| an extraordinary or unusual thing, person, or event; an exceptional example or instance. |
medullary sheath n.
See myelin sheath.