There is little doubt that in this case the primary contraction was due to imperfect evolution of the ligaments, and that the shortening of the tendons was secondary. The reason for accepting this order of phenomena is that a pure myogenic contraction does not readily lead to changes in the joint structures, because the articulations are capable of full extension while the flexor tendons are relaxed by bending the wrist, and hence the limitation of movement is not constant. (See Case recorded on page 58.) On the other hand, in a permanent contraction of a finger-joint occurring during the period of active growth the flexors are never stretched to their full extent, and consequently do not undergo their normal longitudinal development; but should such a contraction originate in an adult the case is different, as muscle and tendon show very little disposition to undergo active involution in the direction of their length after their complete development is attained; and hence after division of the abnormal bands in true Dupuytren’s disease the tendons do not impede the complete extension of the digit. This law, that joint contractions commencing in youth lead to shortness of muscle tendon, while those beginning in adult life do not, is worthy of the attention of the surgeon. _Pathology._—The affection is of some pathological importance, because it affords a simple test case by which many other questions of larger moment may be decided. It has been demonstrated that the permanent obstacle to extension of the contracted joint is to be found in the ligaments, there is no evidence of either muscular or nervous impairment or of any inflammatory changes in or about the joint, the process of contraction is slow and painless, and the condition always originates and progresses to its maximum during the term of active growth. In order to understand the significance of the complaint, it is necessary to dwell upon some facts in digital anatomy and physiology that have not received the consideration they deserve. If we examine a number of hands, it will be found that there is a remarkable wide physiological variation in the range of movement at the phalangeal articulations in different individuals, and it requires but a small departure outside the physiological limits of variation to constitute the pathological deformity under consideration. The results of my own observations are as follows: (1) At each of the digital joints the distal bone, starting from the position of extreme flexion, passes through a variable number of degrees before it reaches the point at which it is arrested by tension of the ligaments. In the metacarpo-phalangeal joint the angle formed between the two bones during extreme flexion is usually about 80°, and the entire extending movement from this point may be represented in the healthy hand by any number of degrees between 90 and 190. That is, in one person the motion is arrested a little before the axis of the phalanx