FLEXOR PROFUNDUS DIGITORUM AND LUMBRICALES. 



227 



phalanx the tendon of each finger passes through the opening formed for its trans- 

 mission in the tendon of the flexor sublimis, and it is inserted into the base of the 

 last phalanx. 



The index finger portion of the muscle is usually separate throughout : it arises mainly 

 from the interosseous membrane, and only to a slight extent from the adjacent part of the 

 ulna. The middle and ring finger portions arise in close connection chiefly from the anterior 

 surface of the ulna, but also from the inner surface of the bone and the aponeurosis of the 

 flexor carpi ulnaris near the elbow, and by a few fibres from the interosseous membrane 

 below. The little finger portion arises from the hinder part of the inner surface of the ulna 

 and the aponeurosis of the flexor carpi ulnaris. Between the ring and little finger portions a 

 considerable part of the inner surface of the ulna is free from muscular attachment. 



Relations. The upper extremity of the flexor profundus embraces the insertion of the 

 brachialis anticus. In the forearm the muscle is covered by the flexor carpi ulnaris and flexor 

 sublimis digitorum, and on it lie the median nerve and the ulnar vessels and nerve. The 

 external border is adjacent to the flexor longus pollicis, from which it is separated on the 

 interosseous membrane by the anterior interosseous vessels and nerve. 



The lumbricales muscles are four tapering fleshy fasciculi, passing from the 

 tendons of the flexor profundus to the tendons of the common extensor. Each 



Fig. 237. BONES OP TWO FINGERS, WITH THE INSERTIONS OF THE TENDONS. (R. Quain.) 



In A, the tendons of the flexor muscles are bound to the bones by the fibrous sheath. In B, the 

 sheath has been removed, as well as the vincula accessoria ; 1, metacarpal bone ; 2, tendon of the flexor 

 sublimis j 3, tendon of the flexor profundus ; *, perforation of the sublimis by the profundus tendon ; 

 4, tendon of the extensor communis digitorum; 5, lumbricalis muscle ; 6, one of the interosseous 

 muscles. 



muscle arises by fleshy fibres from the outer or radial border of one of the deep flexor 

 tendons, and in the case of the two inner muscles also from the ulnar border of the 

 second and third ; proceeding downwards and then backwards on the radial sides of 

 the fingers, each is inserted into the expansion of the extensor tendon on the dorsal 

 aspect of the metacarpal phalanx. 



Varieties. The index finger portion of the flexor profundus often receives fibres from 

 the upper part of the radius, close to the interosseous membrane. The muscle may be joined 

 by a slip given off from the inner head of the flexor sublimis, or arising separately from tha 

 internal condyle of the humerus or the coronoid process of the ulna : in some cases this slip 

 constitutes an accessory muscle, which joins very variously one or more of the perforating 

 tendons. A connection with the flexor longus pollicis is not unfrequent, generally in the 

 form of a slip passing from that muscle to the index finger tendon of the flexor profundus. 



Varieties of the lumbricales muscles are of frequent occurrence. Their number is occasion- 

 ally diminished to three, or even to two, and in rare instances is increased to five or six. The 

 destination of one or two of them is often changed, and one finger (most frequently the 

 middle or ring) has sometimes two inserted into it. Lastly, one muscle may be inserted into 

 two fingers. The fourth has been observed to take the place of the fourth perforated tendon 

 of the flexor sublimis. 



Synovial bursa. The tendons of both the superficial and deep flexors are enveloped 

 beneath the annular ligament in a large and loose synovial sac, which extends upwards to 

 the level of the radio-carpal articulation, while downwards it is prolonged along the inner 

 tendons to the beginning of the digital sheath of the little finger, into which in most cases it 



VOL. II. Q 



