_Pathology._—The explanations of the peculiar movement which characterises the disease are for the most part of a purely theoretical character, for, as might be anticipated, the opportunities for direct examination of the structures have been extremely rare. It speaks highly indeed for the ingenuity of our investigators that so many plausible hypotheses have been constructed upon so small a basis of observed fact. The views now open for consideration are as follow: (1) The development of a fringe or other growth in the synovial sheath of the flexor tendons. Such a tumour lying in the synovial cul-de-sac, which projects beyond the proximal end of the tendon sheath when the fingers are flexed, would be drawn within the theca during extension of the digit, and might in this way oppose a resistance to the movement which would be overcome as soon as the body had passed the constricted entrance of the theca. (2) A nodose condition of the tendon due to the development of a growth within the tendon or upon its synovial investment. Such a nodosity is said to have been unmistakably palpable in many cases; but in two examples examined by Carlier, where the tactile impression of a node was remarkably strong, the tendons were found perfectly healthy at the point of examination. On the other hand, Leisering of Hamburg actually exposed a nodosity in the profundus tendon at the level of the point at which it entered the canal of the flexor sublimis, excised it, and cured the disease. In another case a fringe-like tumour was discovered springing from the synovial covering of the flexor sublimis. The nodosity accepted as a fact, the “spring” phenomenon accompanying must be explained by the varying resistance of different parts of the theca, the impediment occurring at either of the firm, resistant portions of the canal which lie at the proximal opening of the sheath and opposite the shafts of the first and second phalanges, and the sudden release occurring at the weaker points, just above the metacarpo-phalangeal joint, and in front of the first inter-phalangeal articulation. In the case of the thumb, however, the fibrous sheath is much thinner than in the fingers, and the variations of strength in its different parts are comparatively slight after the inter-sesamoid portion of the canal is passed. An obstruction offered to a nodule in the flexor profundus by the channel in the flexor sublimis has been proposed as a cause; but although this might be accepted for the fingers, it would not apply to the thumb, which has but one tendon within its theca. (3) An alteration in the shape of the articular surface, such as was first pointed out by König in hammer toe. In these cases the movement of the distal bone is intercepted by the presence of a ridge extending transversely across the head of the proximal bone, and when by voluntary or passive force the ligaments are made to yield sufficiently to allow the obstacle to be