A remarkable case reported by Sir William MacEwen in the Royal Society’s _Phil. Transactions_, Series B, Vol. 199, pp. 253, 279, is worth referring to in this connection. It was a case of a growth of bone in muscle connected with an old injury to the thigh of a man 38 years old, and healthy. At the operation performed by the author of the paper the tumour was found to be movable, partly attached to the fascia lata of the thigh, and the upper part of the tumour moved on the lower. It was found that the tumour consisted of two parts, the upper three-and-a-half and the lower seven inches long, altogether a mass about ten inches in length. Muscular bundles of the vastus externus were included in this ossific formation, one passed through a tunnel in the bone through which it worked, and the sides of it were polished. _At the point where the newly formed bone came in contact the surfaces fitted each other and were polished as if they were covered with cartilage, and were here surrounded by a capsule._ (Italics not in original.) This fibrous covering when opened was seen to contain a thin serum, which, though not of the consistence of synovial fluid, still aided in lubricating the polished surfaces as they played over one another. A similar case was reported also by Dr. C. Paterson, surgeon to the Glasgow Royal Infirmary. A very interesting address by the Hunterian Professor, Mr. Jonathan Hutchinson, was given in February, 1917, on Dupuytren’s work, especially in the discovery of the cause and treatment of the contraction of palmar fascia known by his name. Professor Hutchinson described his method of curing this by the removal of the head of the first phalanx, and showed excellent results and evidence of the formation of a perfect new joint to take the place of the old distorted one, and the fingers were as efficient as in the normal state in the exercise of flexion. He gives photographs of the hand some months after the operation showing it to be capable of easy and full extension as well as of flexion. This again agrees well with the cases of Sir W. MacEwen and Dr. Paterson of the formation of a functional joint _by_ use and habit.