interosseous membrane, and gains the posterior aspect of the limb. It supplies muscular twigs to the three deep muscles with which it is in contact. In addition to these it gives off the following branches : 1. Median. 2. Medullary. 3. Anterior communicating. The median artery is a long delicate vessel, which accompanies the median nerve. The medullary arteries are two in number-one for the radius, the other for the ulna. They enter the nutrient foramina of these bones. The anterior communicating is a slender artery, which runs downwards, behind the pronator quadratus, to join the anterior carpal arch. The Anterior Interosseous Nerve (nervus interosseus volaris) is a branch of the median, and accompanies the artery of the same name. It does not follow it, however, through the interosseous membrane, but is distributed entirely upon the front of the limb. It is the nerve of supply for the flexor longus pollicis, the outer part of the flexor profundus digitorum, and the pronator quadratus, whilst its terminal filament proceeds downwards, behind the last-named muscle, to help in the supply of the carpal joints. WRIST AND PALM. In this dissection we meet with the following struc tures: 1. Palmaris brevis and the palmar cutaneous nerves. 2. Palmar fascia. 1 The flexor profundus digitorum is therefore supplied by two nerves, viz., the ulnar and the median. The precise range of supply by each of these nerves is somewhat variable. As a general rule the division of the muscle which belongs to the index finger is supplied by the median and the part belonging to the little finger by the ulnar; whilst the portions belonging to the middle and ring digits receive filaments from both nerves. 3. Superficial palmar arch and its branches. 4. Median and ulnar nerves and their branches. 5. Anterior annular ligament, the flexor tendons, and the flexor sheaths. 6. Lumbrical muscles. 7. Short muscles of the thumb and little finger. 8. Deep palmar arch and its branches. 9. Arteria princeps pollicis and arteria radialis indicis. Surface Anatomy. In the centre of the palm the depression, known as the "hollow of the hand," may be remarked. Along the ulnar border of the palm this is bounded by a rounded elevation, called the hypothenar eminence, which is produced by the subjacent short, intrinsic muscles of the little finger. The thenar eminence, or ball of the thumb, formed by the short muscles of that digit, is the marked projection which limits the palmar hollow above and on the outer side; whilst the transverse elevation above the roots of the fingers, which corresponds to the metacarpo-phalangeal articulations, constitutes the lower boundary of the central palmar depression. Two pronounced bony projections on the front of the wrist cannot fail to attract attention when the hand is bent backwards. The more prominent of the two is situated at the upper extremity of the thenar eminence, and is formed by the tubercle of the scaphoid bone and the vertical ridge on the front of the trapezium; the other is placed at the upper end of the hypothenar eminence, and is somewhat obscured by the soft parts attached to it. It is caused by the pisiform bone, and when taken firmly between the finger and thumb a slight degree of gliding movement can be communicated to it. Traversing the thick integument of the palm, three strongly-marked furrows are apparent. One of these begins at the elevation formed by the scaphoid and trapezium, and curves downwards and outwards around the base of the thenar eminence to the outer margin of the hand. A second crosses the palm transversely. Commencing at the middle of the outer border of the hand, where the first furrow ends, it runs inwards, but, as a general rule, it fades away upon the hypothenar eminence. The third furrow begins near the cleft between the index and middle fingers, and proceeds inwards with a gentle curve across the hypothenar eminence FIG. 26.-Diagram to show the relation of the skin markings to the inner margin of the hand. The transverse cutaneous furrows at the roots of the fingers, and on the palmar aspects of the interphalangeal joints, should also be noticed, and it should always be remembered that, except in the case of the proximal interphalangeal joints, these do not correspond accurately with the subjacent articulations. The furrows at the roots of the fingers are placed at least one inch below the metacarpo-phalangeal joints, whilst the distal interphalangeal furrows lie slightly higher than the corresponding interphalangeal joints. The upper of the two furrows in front of each of the proximal interphalangeal joints is placed immediately over the articulation. Reflection of Skin.-In the first instance the skin should only be raised from the palm. Two incisions are required, viz.—(1) a vertical incision along the middle line of the palm; (2) a transverse cut across the roots of the fingers from the ulnar to the radial margin of the hand. The skin is tightly bound down to the subjacent deep fascia, and it must be raised with care. More especially is it necessary to proceed with caution at the roots of the fingers in order that some transverse fibres constituting a superficial cutaneous ligament may be preserved. In reflecting the inner flap of integument it is well not to lift it quite as far as the ulnar border of the hand, because it is into this portion of skin that the palmaris brevis is inserted. Superficial Structures.-The superficial fascia over the central part of the palm is dense and thin. The fat is subdivided into small lobules by fibrous septa which bind the skin to the subjacent palmar fascia. Towards the ulnar and radial margins of the hand the fat becomes softer, and the amount of fibrous tissue in its midst diminishes. connection with the superficial fascia of the palm we have to study-(1) the palmaris brevis; (2) the superficial transverse ligament; and (3) the palmar cutaneous nerves. In The palmaris brevis is a small cutaneous muscle embedded in the superficial fascia which covers the upper part of the hypothenar eminence. If it has not already been exposed by the reflection of the skin, carry the knife transversely through the granular fat on the ulnar margin of the palm immediately below the anterior annular ligament. The fleshy bundles of the muscle will come into view. When these have been cleaned, the muscle will be seen to consist of a series of distinct fasciculi, which in its lower part are frequently separated from each other by intervals of varying width. It constitutes a thin fleshy layer, which covers an inch and a half or more of the hypothenar eminence. Externally it takes origin from the anterior annular ligament and inner border of the central part of the palmar fascia, whilst internally its fasciculi are inserted into the skin over the ulnar margin of the hand. The palmar cutaneous nerves are three in number, and they arise, as already noted, from the ulnar, median and radial nerves. They should now be traced to their ultimate distribution in the palm of the hand. The transverse superficial ligament is a band of fibres which extends across the palm at the roots of the fingers. It is intimately connected with the skin, and is enclosed within the folds of integument in the clefts between the fingers. Dissection. The palmaris brevis should be reflected by detaching its fasciculi from their origin, and turning them inwards. In raising the muscle care must be taken of the ulnar artery and nerve, which lie under cover of it, and a little nerve-filament from the latter should be traced into its substance. The granular fat should next be removed from the palm, and the dense palmar fascia cleaned. Towards the roots of the fingers the digital vessels and nerves, together with the lumbrical muscles, appear in the intervals between the slips into which the palmar fascia divides. These should be defined, and it will be seen that they pass downwards under cover of the superficial transverse ligament. Having noted this point, remove the ligament. The digital arteries and nerves for the inner side of the little finger, and the outer side of the index, appear beyond the area of the central part of the deep fascia, higher up than the others, and are consequently liable to injury, unless it be remembered that they occupy this position. Palmar Fascia.-The deep fascia of the palm is composed of three portions-a central and two lateral. lateral parts are thin and weak, and are spread over the muscles which constitute the thenar and hypothenar eminences on the outer and inner margins of the palm. The central portion of the palmar fascia, on the other hand, is exceedingly strong and dense, and is spread out over the middle of the palm. It counteracts the effect of |