1. Paralysis caused by anterior nerve root section, or by peripheral nerve section, leads to marked changes in the bones and muscles of the affected limb in experimental animals. Vascular changes are not the cause of the bone atrophy in a paralysed limb.

2. The altered properties of the bones of a paralysed limb are due almost entirely to a loss in the quantity of bone; bone quality is only slightly altered.

3. The bone changes that follow paralysis are due to the secondary loss of muscular activity. No evidence could be obtained that nerves exert any specific, trophic influence on bone.