grey commissure grey commissure the grey commissure is a thin strip of grey matter that surrounds the central canal of the spinal cord and, along with the anterior white commissure, connects the two halves of the cord. it comprises lamina x in the rexed classification. grey commissuremedulla spinalis - substantia griseaspinal cord. (grey commissure is #3, near center.)detailsidentifierslatincommissura grisea anterior medullae spinalis, commissura grisea posterior medullae spinalisneuronames1665, 1649fma77036anatomical terms of neuroanatomy