We have considered two very diverse orthopaedic condition, both of which are associated with neurofibromatosis. Considered superficially, these two conditions are about as much alike as blck and white. As we have said previously, the neurofibroma itself is unobtrusive, and the associated pathology is the condition which attracts attention to itself, from both the patient and medical man.

We have expressed our opinion that the bone changes we have studied in these cases are all due to lack and control of the ordinary growth processes of bone. Under this general heading of uncontrolled growth we would classify the changes found as follows:

1. Hypertropiiy, Or overgrowth, as illustrated in the nicrease in increase in length of members.

2. Hypotrophly, or underdevelopment as illustrated in the small tarsal bones Cases 3 and 4.

3. Distortions of growth as shown by the vertebrae in Case 4.

4. Changes in the constitution of bone as exemplified by its failure to unite after fracture.

These four changes seem to include the bone changes as we see them, both in our own cases and in others described in the literature. The changes seen in a case may fit into more than one of these classes.

We believe that these bone changes are not merely associated with, but are the result of, the changes in the nerve either directly or indirectly. The reason for this belief is the frequency of the signs of neurofibromatosis associated with the types of deformity we have studied. However, the converse that these deformities always accompany signs of neurofibromatosis does not hold good. The most convincing argument for the causal relationship is the segmental localization of the deformities. This holds good not only in our cases but in many reports in the literature. The finding of definite endarteritis, to which we have called attention, is of special interest. We believe that it is a fairly constant finding. One point of interest is the effect that such an endarteritis might have on other organs. For instance in the brain it might account for mental changes which frequently accompany neurofibromatosis. Again, if it occurs in the arteries supplying any of the ductless glands, it is quite conceivable that dysfunction might result in that particular gland and a peculiar chain of symptoms be initiated. This may account for much of the rather indefinite endocrine symptomatology. Still another point of interest in this finding of endarteritis is whether it may furnish a clue to what we have called the uncontrolled growth of parts of the body. The arteries are under the control of the autonomic nervous system. May not this system also have some control of the normal pattern of body growth? We must admit we do not have enough evidence to advance it as an hypothesis but the idea is intriguing.