The weight of the skeleton is due, only in part, to the size or the volume enclosed by the surface of its individual bones. The size of the bones is determined by the many factors included in both heredity and environment. I t is generally believed that after growth is completed there is no si,&ficant change in the size of the normal skeleton, or of any bone comprising it, throughout the life span. However, bones are living organs and their maintenance is dependent on metabolic processes which lmay be affected by many factors, including stress, activity, growth and aging. Evidence of these effects is apparent in the internal structure of a bone through alteration in the amount and density of its deep, spongy substance (substawtia sportgiosa) and its superficial, compact substance (substawtia compacta).Koch ('17) considered the conformation of the intrinsic structures of the femur to be the result of adaptation to stress of pressure and function. A more realistic view has been presented by Murray ( '36) who recognized that the primary patterns of the skeleton are well defined early in life and that environmental conditions act as modifiers of the hereditary intrinsic patterns. The importance of functional stresses in maintaining the characteristic structures of bones is indicated by the work of Amprino ('38) who showed that, when normal movement of the limbs is inhibited, degenerative processes akin to osteoporosis set in. Sperling et al. ( ' 5 5 ) studied 'This investigation has been aided in part