214 MUSCLES OF THE UPPER LIMB. 



of the deep flexor tendons, and in the case of the two inner muscles also 

 from the nhiar border of the second and third, and proceeding forwards 

 to the radial sides of the fingers, each is inserted into an expansion of 

 the extensor tendon on the dorsal aspect of the metacarpal phalanx ot 

 the finger. 



Varieties. — The flexor profundus often presents varieties in its origin, deriving 

 fibres from the radius in some instances, a distinct slip from the coronoid process 

 of the ulnar in others, and more rarely from the inner condyle of the humerus. 

 It is not imfrequently connected -^'ith the flexor sublimis, or with the flexor 

 longus poUicis. The distinct slip from the coronoid process constitutes in nume- 

 rous cases an accessory or supplemental muscle wkich joins very variously one or 

 more of the perforating tendons. 



The varieties of the lumbricales muscles are of frequent occurrence. Their 

 number is sometimes diminished to three, and in rare instances is increased to five 

 or six. The destination of cne or two of them is often changed, and one finger 

 (most frequently the third or foirrth) has sometimes two inserted into it. Lastly, 

 one miiscle may be inserted into two fingers. The fourth has been observed to 

 take the place of the fouirth perforating tendon of the flexor profundus. 



The flexor longus poUicis mnscle, placed side by side with the flexor 

 profnndns digitorum, arises from the anterior grooved surface of the 

 radius from the oblique line to the edge of the pronator quadratus ; 

 it arises also from the adjacent part of the interosseous ligament, and 

 sometimes by a rounded fleshy and tendinous slip, distinct from the rest 

 of the muscle, from the inner part of the coronoid process. The muscle 

 ends in a tendon which passes behind the annular ligament of tlie wrist 

 close to the trapezium, turns outwards between the two heads of the 

 flexor brevis and between the sesamoid bones, and, entering a canal 

 similar to those of the other flexor tendons, is finally inserted into the 

 base of the second phalanx of the thumb 



Varieties. — A very common variety in this muscle (in two-fifths of subjects 

 dissected by Macalister) is the existence of a second or accessory tendon for the 

 thumb : this may arise from the flexor sublimis, the coronoid process, or some- 

 times as far up as the mtemal condyle. The flexor longus pollicis is also some- 

 times connected by a slip with the flexor .sublimis or jjrofimdus, or the i^ronator 

 teres. A tendon of insertion iaito the index finger- has also been observed. 



The pronator quadratus, placed close to the bones behind tlie last 

 two muscles, arises from the anterior and inner surfaces of the ulnar 

 for about two inches above its carpal extremity ; its fibres cross the 

 lower part of the forearm, some transversely and others obliquely, 

 and they are inserted for an equal distance into the fore nart of the 

 radius. 



Varieties. — The pronator quadi-atus is subject to varieties, chiefly as follows : — 

 1. It may be entu-ely absent, but tliis is rare ; 2, it is subdivided into two layers, 

 or occasionally into three ; 3. it extends farther iip wards on the bones of the 

 forearm than usual ; 4, it is jirolonged downwards on the carpus, in some cases 

 as a radio-carpal, and in others as an ulno-caiiDal muscle (Macalister, Journ. of 

 Anat., vol. v., W. Griiber, loc. cit.). 



Nerves. — The muscles of the pronator and flexor group receive their nerves 

 in great part from the median : only one muscle being wholly supplied from the 

 ulnar nerve. The branches from the median are distributed to the muscles in 

 two groups, one to the sujierficial and another to the deep set. From these the 

 anterior interosseous is a distinct branch, wliich accompanies the anterior inter- 

 osseous \ essels in front of the mterosseous ligament, and ends in the pronator 



