248 SURGICAL APPLIED ANATOMY. [Chap. xv. 



fact that abscesses of the thumb and little finger are 

 apt to be followed by abscesses in the fore-arm, while 

 such a complication is not usual after suppuration in 

 the remaining fingers. The synovial sac for the 

 flexor tendons is narrowed as it passes beneath the 

 annular ligament, and thus it happens that when 

 distended with fluid or with pus, it presents an 

 hour-glass outline, the waist of the hour-glass corre- 

 sponding to the ligament. The two synovial sacs be- 

 neath the ligament sometimes communicate with one 

 another. 



In one form of whitlow, that form where the pus 

 occupies the synovial sheaths of the tendons on the 

 fingers (thecal abscess), the suppuration can often be 

 seen to end abruptly where the sheath ends, when the 

 index, middle, or ring-finger is involved, viz., opposite 

 the neck of the corresponding metacarpal bones. In 

 another form of whitlow (the abscess in the pulp at 

 the end of the finger) the periosteum, of the third 

 phalanx is readily attacked, there being no inter- 

 vening tendon sheath over that bone. In this 

 affection the bone often necroses and comes away, 

 but it is significant to note that it is very seldom that 

 the whole of the phalanx perishes. The upper part, 

 or base, of the bone usually remains sound, and is 

 probably preserved by the insertion of the flexor 

 profundus tendon. It is also interesting to bear in 

 mind that the base of the bone is an epiphysis that 

 does not imite to the shaft until the eighteenth or 

 twentieth year. 



Beneath the posterior annular ligament there are 

 six synovial sheaths for tendons, corresponding to the 

 six canals formed by that ligament. The sheath most 

 frequently inflamed is that for the extensores ossi meta- 

 carpi and primi internodii pollicis. It runs from 

 a point about three-quarters of an inch above the 

 radial styloid process to the first carpo-metacarpal 



