A. Skeleton of finger with lateral ligaments; 1. Metacarpal bone; 1_a_. Anterior fibres of lateral ligament blending with glenoid plate; 2. Metacarpal phalanx; extension checked by short anterior fibres of lateral ligament (1_a_) at line of metacarpal axis; 2_a_. Super-extension permitted when 1_a_ long; 3 and 3_a_. Middle phalanx under conditions similar to 2 and 2_a_; 4 and 4_a_. Ungual phalanx.—B. Hammer finger; extension at first inter-phalangeal joint arrested by imperfect longitudinal development of anterior fibres of lateral ligament.—C. Palmar aspect of first inter-phalangeal joint (left middle finger); 1. Metacarpal phalanx; 2. Middle phalanx; 3. Anterior fibres of lateral ligament decussating with those of the opposite side; 4. Glenoid plate.] It may be of advantage to describe the articular structures of one of the finger-joints somewhat in detail. The capsule of an inter-phalangeal joint is formed on the dorsal aspect by the expansion of the extensor tendon, reinforced by the transverse fibres (the _ligamenta dorsalia_ of Henle), which bind the tendon to the bone and lateral ligaments; on the palmar surface of the articulation is a glenoid plate of fibro-cartilage firmly attached to the anterior border of the distal bone, but very feebly connected with the neck of the proximal bone, and fused intimately with the anterior fibres of the lateral ligaments; lastly, at the sides of the joints are the radial and ulnar lateral ligaments, the attachment of which it is important to study closely, as they are often imperfectly described in anatomical text-books. The fibres of each lateral ligament are attached above to a little tubercle at the side of the head of the first phalanx, and from this point they radiate in a fan-like manner—the more posterior passing to the side of the base of the second phalanx, the rest blending with the glenoid plate, and through the intermediation of this are connected with the anterior border of the base of the distal bone, decussating to some extent with fibres of the opposite ligament. (Fig. 7, C.) The strongest part of the glenoid plate, in fact, is made up of these ligamentous fibres; and it is these which, relaxed in flexion, become progressively more and more stretched during extension, and at length by their tension bring the movement to a close, but, as already shown, the point at which the maximum tension is reached varies to a large extent in different individuals.