(Darwin 1897, 123) referred to the term “spinal marrow” when comparing the shape of the foramen magnum in wild rabbits versus large “lop-eared” rabbits. After looking up the term “marrow,” (which refers to the fat in the middle of bones from which blood is formed,) I found that the term is also used to refer to the spinal cord. Interesting.
Darwin, Charles. The variation of animals and plants under domestication, Volume I. New York: D. Appleton and Company, 1897.