Five cases of macrodactyly are presented, in all of which pathological changes were found in the peripheral nerves. In one (a young adult), the changes were definitely classed as due to a neurofibroma. In the four others (all young children), the changes were an increase in endoneurial fibrous tissue, with evidence of degenerative changes in nerve fibers. Three of the four children showed at least some of the clinical stigmata of neurofibromatosis. It would seem then that the changes shown in these nerves may represent an early stage in the development of a neurofibroma. Case 3 is particularly suggestive in this regard.

The fact that local hypertrophy is so constantly associated with peripheral nerve pathology, would seem to indicate that there is a relationship between them. It is believed that the nervous system exerts some controlling action on the process of growth, and that the impaired nerves fail in this function, resulting in uncontrolled or uninhibited growth. Whether there are changes in the central nervous system which result in the change in the peripheral nerves is not known.

These observations seem to favor the neurogenic theory as the origin of at least certain types of congenital deformities. The author feels that the investigation of pathology in the peripheral nerves has been somewhat overlooked, and that more careful work along this line might be of great interest.