Marrow

A substance composed of water, fat, and albuminous matter, existing in the cavities of many of the long bones. M.-cell, a cell resembling a white blood-corpuscle, but larger and with a clearer protoplasm and a larger nucleus, and showing ameboid movement. It is found in the marrow of bones. M., Fetal, the juicy, red marrow filling the cavities of the fetal endochondral bones. M., Red, the reddish marrow, quite free from fat, contained near the articular extremities of long bones. M., Spinal, the spinal cord. M., Yellow, the fatty marrow of the shafts of long bones.