92 Anatomy Applied to Medicine and Surgery. 



one side of the phalanx to the other, so as to form arches 

 over the tendons, but all the fibres are not transverse, since, 

 opposite the interphalangeal joints they are arranged so as 

 to somewhat resemble a lattice work. Underneath the deep 

 palmar fascia is (4) the superficial palmar arch, a con- 

 tinuation downwards of the ulnar artery, which, passing 

 over the annular ligament on the radial side of the pisi- 

 form bone, enters the palm, and is directed in a curved 

 manner towards the cleft between the metacarpal bones of 

 the little and ring fingers. The artery then passes under- 

 neath the deep palmar fascia and ends, about the junction 

 of the upper and middle thirds of the metacarpal bone of 

 the index finger, anastomosing with the superficialis volae 

 from the radial. The superficial palmar arch supplies the 

 fingers by digital branches, and lies on the flexor tendons 

 and on the divisions of the median nerve. These divi- 

 sions of the median nerve supply some of the muscles of 

 the thumb and the two outer lumbricales and are then dis- 

 tributed to the thumb, index, middle and half of the ring 

 fingers. 



(5) The synovial sheaths for the flexor tendons in the 

 palm are two in number one for the flexor longus pollicis, 

 and the other for the flexor sublimis and the flexor 

 profundus digitorum. The former sheath, i.e., the one 

 for the flexor longus pollicis tendon, extends from about 

 one inch above the annular ligament to the base of the last 

 phalanx of the thumb, whereas, the sheath for the other 

 is larger and extends from ,about one and a half inches 

 above the annular ligament, to the middle of the metacar- 

 pal bones below. In the case of the little finger, however, 

 this sac does not end at the middle of the metacarpal bone, 

 but extends down to the base of the phalanx of that finger, 

 so that the synovial sheaths for both thumb and little fin- 

 rer communicate with the synovial sacs beneath the 



