It is perhaps not easy to say what is meant by the expression “palmar fascia,” since the text-books are by no means agreed upon the point. We have really to notice four palmar structures which may claim a share in the title. These are (1) the radiating fascia, spreading towards the fingers from the palmaris longus and annular ligament; (2) the aponeuroses investing the muscles of the thumb and fingers; (3) a delicate connective tissue blending with 1 and 2 and forming sheaths for the flexor tendons, the lumbricales, and the digital vessels and nerves; (4) the fascia of Gerdy, which runs transversely across the bases of the second, third, fourth, and fifth fingers and in the inter-digital webs, and is continuous with the superficial fascia of the digits and dorsal surface of the hand. Lastly, in addition to these, we might regard the ligamenta vaginalia and the transverse ligaments connecting the metacarpo-phalangeal articulations as specialisations of the family. We are, however, mainly concerned with the radiating fascia and fibres of Gerdy. The _radiating fascia_ consists of a strong fibrous expansion extending subcutaneously from the anterior annular ligament and palmaris longus tendon, and consisting of an outer or thenar portion, spreading over the muscles of the thumb and blending with the muscular aponeurosis; an inner or hypothenar portion similarly related to the muscles of the little finger; and a central digital expansion which is derived almost entirely from the palmaris longus when this is present, but is well developed even when the muscle is wanting. The central portion spreads out in a fan-like manner as it approaches the fingers, giving off some strong fibres from its anterior surface through the palmar fat to the connective tissue of the superjacent corium, especially in the situation of the palmar folds, and attached by its deep surface to the delicate fascial investment surrounding the tendons, vessels, and nerves; finally, a little beyond the middle of the palm it divides into four segments, one for each digit, each of which soon breaks up into two lateral bands that embrace the sides of the metacarpo-phalangeal joint to blend with its ligaments and the periosteum of the first phalanx, and running on become similarly connected with the first inter-phalangeal joint and middle phalanx. Where the four digital bands diverge they are joined together by deep transverse fibres which pass from the inner to the outer border of the hand, blending in these situations with the muscular aponeurosis. (Fig. 2.) [Illustration: FIG. 2. THE PALMAR FASCIÆ.