“Red blood cells are produced by the long bones of the body such as those found in the shins, thighs and arms. They circulate oxygen and eliminate carbon dioxide.
“White blood cells are produced by the flat bones such as the pelvis, sternum, scapulae and skull. They are vital to the body’s defense system. Both red and white blood cells are produced in the marrow of the bones; which type of cells are produced depends on the type of marrow that predominates.
“Healthy bones contain more red marrow, which produces blood cells. Yellow bone marrow also exists, producing fat which accumulates as the body ages. When neglected through lack of exercise, this accumulation can decrease the proportion of red marrow crucial to the production of blood.
“Although yellow marrow can also produce blood cells, healthy blood production is contingent upon a higher proportion of red marrow in the bones and less fat. For this reason, Bone Marrow Nei Kung practitioners always seek to increase the growth of red marrow while eliminating fat.”
From Bone Marrow Nei Kung, By Mantak Chia