On account of our inability to exclude the indirect effect of sensory and circulatory influences, the results of many experiments undertaken to prove the existence of special trophic nerve centers can always be questioned. This also is true of our clinical and neurologic observations which would seem to compel the inference that trophic centers direct the metabolism of muscles and bones.
Bone atrophy is found in many pathologic conditions affecting bone, muscle, skin and the nervous system. The bone changes found in syringomyelia and tabes are well established facts in medical literature. The many peripheral nerve injuries sustained during the late war offer a substantial contribution in evidence of the close connection between nerve injury and bone atrophy. The pathologic condition with which bone atrophy is associated may be due to inflammation of the joints, bones or muscles, or it may be caused by injury, such as fracture. Such an