In summarizing it seems very hard at the present time, either from the evidence presented by many authors, or from our own observations, to draw definite conclusions as to the etiology of the progressive muscular dystrophies. If we allow ourselves to be influenced entirely by the theories of endocrine origin we find many stumblingblocks. It is hard to believe that a cystic tumor or other pathology of one of these glands can always locate itself in just the place to cause repeatedly the identical or almost identical clinical entity. The evidence introduced in this respect does not always seem to be entirely sound. On the other hand, the recoveries reported in the literature and in our own series seem to be beyond question. There is not in progressive muscular dystrophy the low fatigue coefficient, within physiological limits, that one would expect to find. The muscle fibers which remain unaffected from the disease seem to be acting to the extent of their normal limit. But there seems to be not "enough ammunition to go around." Is it a matter of waste product elimination? Are a part of the muscle fibers in their physiological capacity of glycogen builders and storehouses, or as secretors of sarcolactic acid and carbon dioxide, failing in their work?

It is generally conceded that there is a low amount of blood sugar, and that sugar when fed is rapidly excreted. Has something happened to the muscular substance which should activate the transforming enzyme? We need more autopsies; we need more pathological studies; more chemical studies; and we need more research by men who go into their work with a good substantial knowledge of what has already been said and done on the subject.

In making this synopsis of our cases we have come to the realization of its possibilities, and the meager work which we have presented will be followed up in the immediate future by a more thorough, and we trust, more enlightening series of experiments.

I am indebted to Dr. Steindler, in charge of the Orthopaedic Service, for the privileges extended me in the use of the cases and for his co-operation and valuable advice.