82 ANATOMY IN A NUTSHELL. 



Origin.— One head from internal condyle of humerus by common tendon; 



the other from inner margin of olecranon, upper two-thirds of posterior border 

 of ulna by an aponeurosis common to it, the Extensor carpi ulnaris, and Flexor 

 profundus digitorum, and also from the intermuscular septum. (Plate XXIII.) 



Insertion. Pisiform bone, annular ligament, and base of fifth meta- 

 carpal and unciform bones. (Plate XXVII.) 



Ai in i\. Flexes wrisi . 



\'u;\ i: Si imma . Ulnar. 



Blood Supply. Ulnar artery. 



Flexor sublimis digitorum (perforatus). Description.— (Plates XXX.) 

 This muscle lies just beneath the preceding and is the largest of the 

 muscles of the superficial layer. It arises by three heads. The fibers 

 pass vertically downward, forming a broad and thick muscle which speedily 

 ■ livides into two planes of muscular fibers, superficial and deep. The super- 

 ficial plane divides into two parts which end in tendonsfor the middle and ring 

 fingers; the deep plane also divides into two parts which end in tendons for the 

 index and little fingers, hut previous to having done so it gives off a muscular 

 slip which joins that part of the superficial plane which is intended for the ring 

 finger. As the four tendons thus formed pass beneath the annular ligament 

 into the palm of the hand they are arranged in pairs, the superficial pair cor- 

 responding to the middle and ring fingers, the deep pair to the index and little 

 fingers. The tendons diverge as they pass onward. Opposite the bases of 

 the first phalanges each tendon divides into two slips to allow the passage of 

 the corresponding tendon of the Flexor profundus digitorum: the two portions 

 then unite and form a grooved channel for the reception of the deep flexor 

 tendon. Finally they subdivide a second time prior to their insertion. 



Origin. (By three heads) first head, (1) internal condyle of humerus by 

 common tendon; (2) internal lateral ligament of elbow-joint; ami (3) inter- 

 muscular septum. Second head, inner side of coronoid process of ulna. Third 

 head, oblique line of radius, from the tubercle to the insertion of the Pronator 

 radii ten-. (Plates XXV-XXIII.) 



1 nsertion. t Plate XXVII.)- Lateral margins of second phalanges about 

 their middle. 



Action. Flexes second phalanges. 



\'u;\ i. Si ppl"5 . Median. 



Hi.< Supply. Radial and ulnar arteries. 



Flexor profundus digitorum. Description.— (Plate XXXI.) This muscle 

 is situated on the ulnar side of the forearm, immediately beneath the su- 

 per fiicial flexors. Its fibers form a fleshy belly of considerable size which 

 divides into four tendons; these pass under the annular ligament beneath the 

 tendons of the Flexor sublimis digitorum. Opposite the first phalanges the 

 tendons pass through the openings in the two slips of the tendons of the Flexor 

 sublimis digitorum. The portion of the muscle for the index finger is usually 

 distinct throughout, bu1 the tendons for the three inner fingers are connected 

 together by cellular tissue and tendinous slips as far as the palm of the hand. 

 Four Bmall muscles, the Lumbricales, are connected with the tendons of the 

 Flexor profundus in the palm. 



